GB2090412A - Ultrasonic testing - Google Patents

Abstract

In order to avoid the necessity for repeated re-calibrations of an ultrasonic testing instrument due to changing dimensions of its electronic components, as well as due to different characteristics of the testing head 316, the material of the test object etc., it is provided that the characteristic data are entered via a keyboard 313 and corresponding digital values are stored in memory 34,35. A microprocessor 31 then sends out sequences of ultrasonic pulses of regularly varying rise/fall times and correlates the measured times with a table that permits matching the closest value to the selected data. During actual operation, the traversing time of the sawtooth wave which controls the horizontal beam deflection on the CRT is compared digitally with a calculated time and a suitable correction signal is applied to a current source which modifies the charging current of timing capacitors so as to match the correct sawtooth traversing time. Additional circuitry 311 provides for on-screen display of the position and dimensions of a detection window, textual information and other data. <IMAGE>

Description

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GB 2 090 412 A

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SPECIFICATION

Improvements in signal processing

5 In ultrasonic testing, for example, echo signals received from a workpiece to be tested are converted to 5

electrical signals and displayed as visible indications on a cathode ray tube (CRT) forming part of an oscilloscope which contains a number of control circuits for controlling the position and intensity of the electron beam of the CRT. Generally, the signal voltage to be measured is applied to one pair of deflection plates, usually called the Y-deflection plates, so that a positive signal voltage causes for example, an upward 10 vertical deflection while a negative signal voltage causes a downward vertical deflection of the electron 10

beam. In order to present signals as time-dependent functions, it is necessary and customary to apply a sawtooth waveform to the horizontal deflection plates, usually called X-deflection plates of the cathode ray tube. The sawtooth voltage is a uniformly increasing voltage which results in a constant horizontal deflection speed of the electron beam, i.e. in theX-direction. During the traversing time tH of the sawtooth voltage, the 15 electron beam is deflected from left to right whereafter it returns very rapidly to its starting position. During 15 the return of the electron beam, the beam current is suppressed so that the return path remains invisible on the CRT. In ultrasonic testing equipment, the ultrasonic signal transmitted into the workpiece traverses a given pathlength while the electron beam moves during the time tH. Accordingly, the ultrasonic signal propagation is correlated with the movement of the electron beam; if, for example an echo signal is received 20 by the transducer during the time that the electron beam moves to the right on the CRT, it is possible to 20

correlate the position of the echo on the CRT with an exact location of the source of the echo in the workpiece, for example a void or fault. However, a correlation of this kind is possible with precision, only if the traversing time tH of the horizontal deflection is adjusted very precisely and can be held constant over as long a time span as desired, regardless of the long or short term stability of the various components of the 25 apparatus. Because a full deflection of the beam up to the right-hand limit requires a given deflection voltage 25 and because the traversing timetH is terminated when that final amplitude is attained, the slope of the rising portion of the sawtooth voltage is a function of the traversing time tH. Normally, the sawtooth voltage is generated in a sawtooth generator with the aid of so-called RC elements, i.e. elements consisting of adjustable analog components, such as resistors and capacitors. The electrical characteristics of these 30 components vary, for example as a function of age, making it necessary to perform tedious recalibrations 30 and adjustments with the aid of calibrated test objects in order to correct the substantial errors which may occur in the traversing time of the electron beam due to long-term changes in the characteristics of the components.

Improved circuits for the generation of sawtooth voltages and the display of images on a CRT are 35 disclosed herein in the context of ultrasonic operations, although it will be understood that the circuits are of 35 more general applications. In the drawings, by way of example:-

Figure 1 is a block diagram of a circuit for generating a sawtooth voltage;

Figure 2 is a block diagram similar to that of Figure 1 and employing a microprocessor;

Figure 3 is a detailed circuit diagram of the sawtooth generator;

40 Figure 4a and Figure 4b are diagrams for illustrating the decrease of the voltage of the sawtooth 40

waveform;

Figure 5 is a block circuit diagram of an ultrasonic testing apparatus;

Figure 6a and Figure 6b are diagrams illustrating the manner of correcting the sawtooth voltage in dependence of the selected traversing time;

45 Figure 7 is a block circuit diagram of a trigger delay circuit; 45

Figure 8 is a block circuit diagram of a time and amplitude gate in an ultrasonic testing instrument;

Figure 9 is a set of diagrams illustrating various signals applied to the cathode ray tube for presenting echo signals and the gate;

Figure 10 is a block circuit diagram similar to that of Figure 8 illustrating additional details of the gate 50 circuit; 50

Figure 11 is an elaboration of the block circuit diagram of Figure 5 and illustrates an ultrasonic testing intrument;

Figure 12 is a front view of one embodiment of an ultrasonic testing instrument;

Figure 13 is an illustration of one sample of textual information displayed on the cathode ray tube;

55 Figure 14 is a block diagram elaborating the circuit shown in Figure 11; 55

Figure 75 is a block circuit diagram of the writing circuit for presenting textual information to the cathode ray tube.

Figure 16 shows the circuit for generating the gate bar of Figure 15.

As shown in the diagram of Figure 1, the sawtooth generator 11 is connected by an output line 107 to a 60 horizontal amplifier (X-ampliifier) 110 which applies an amplified sawtooth voltage 19, having a horizontal 60 traversing time tH, to the horizontal (X) deflection plates 111 of a cathode ray tube 112. The exact setting of a precisely maintained traversing time (rise time) tH and thus a precisely defined slope or rate of increase of the sawtooth voltage 19 is insured by additional circuitry shown in Figure 1, including a Schmitt trigger 12 connected to the output line 107, a flip-flop 121, a counter 13 fed by a clock pulse generator 14, a comparator 65 15 and a digital-to-analog converter 16. 65

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The flip-flop serves to initiate and terminate the sawtooth voltage generated by the generator 11 by applying thereto a gate signal 113 over the line 101. The duration of the gate signal is equal to the traversing timetH of the sawtooth signal. The gate signal is started by the application of an external trigger pulse atthe input 100 of the flip-flop 121 and is terminated by the application of a signal from the Schmitt trigger atthe 5 input 102 when the (final) amplitude of the sawtooth voltage 19 exceeds the threshold of the Schmitt trigger 12, i.e. when the end of the traversing time is reached. Subsequently, the actual duration of the traversing timetH is determined in the following way: The length of the gate signal 113 is converted into a digital value by permitting the counter 13 to count pulses from the clock pulse generator 14 while the gate signal 113 is present so that the final count in the counter 13 represents the actual value of the traversing time tH; this 10 value is transmitted to the comparator 15 via a line 103.

A desired (set point) value of the traversing timetH may be selected by means of the keyboard 17. When the keys are actuated, suitable mechanism known per se, for example key switch mechanisms marketed by the firm Datanetics/Knitter provide digital coding of the selected values according to a known diode matrix scheme, for example.

15 The comparator 15 compares the actual value of the traversing time tH present on the line 103 with the nominal or set-point value of the time tH present on the line 104. If these two values differ, a digital value corresponding to the difference is applied to the A/D converter 16 which puts an equivalent analog signal on the input 106 of the sawtooth generator 11. In a manner to be described below, the sawtooth generator 11 then changes the traversing timetH of the next sawtooth pulse 19. The comparison of the actual and nominal 20 values of the traversing time takes place until these values are identical.

Figure 2 is an illustration of a circuit for performing the process described above. The function of the comparator is performed by a microprocessor 114 which contains the intermediate memory 18 shown in Figure 1 and which also performs a number of monitor and control tasks to be described in detail below. A suitable commercial microprocessor is, for example, the type Z-80, available from MOSTEK, in the category 25 "Microprocessor Devices MK". The operating panel (keyboard) 17 is connected to the microprocessor 114. The microprocessor is connected to a preferably 8-line bidirectional databus 118 for transmitting binary coded data and is further connected to a preferably 8-line control bus for transmitting binary coded control commands. These connections are made from the output lines of the microprocessor via a known input/output circuit, for example an integrated circuit also available from MOSTEK.

30 The essential components of the sawtooth generator 11 are an operational amplifier 115, a resistor R0 and, for example, eight capacitors C-i - C8 which are connected to a suitable voltage source U0 of approximately +70 Volts, for example, by a set of switches St - S8. The switches Sn - S8 are preferably semiconductor switches to be further described with the aid of Figure 3. Each of the switches S-i - S8 is controlled by one of eight control lines 142 connected to the intermediate memory 117. A further switch S9 is controlled by the 35 gate signal 113 via the line 101; this signal is generated in the manner already described upon the occurrence of a trigger pulse atthe input 100 of the flip fop 121 atthe time of release of the sawtooth pulse. The operational amplifier 115 is connected as a non-inverting amplifier and serves as a constant current source togetherwith the resistor R0. Depending on the voltage UE atthe input 140 of the operational amplifier 115, its output 141 carries an associated value i whose value is determined by the value of the resistor R0. 40 If the switch Sg has been opened by the presence of a gate signal 113, any of the capacitors C-i -C8 which are connected up will be charged by the constant current I from a discharged state in which the same voltage U0 had been applied to both the top and bottom plates of the capacitors through the closed switch S9. The charge on the top plates of the capacitors flows to ground through the resistor R0, thereby increasing the potential difference across any capacitor which is connected to the battery U0 through a closed switch S-i -45 S8. As a consequence, the output line 141 carries a linearly decreasing sawtooth voltage 143 whose slope depends on the capacitance of the switched-in capacitors and on the magnitude of the constant current I. The capacitors may be said to represent a coarse setting of the traversing timetH while the magnitude of the current I, which depends on the voltage UE, makes possible a fine adjustment of the traversing time tH. When the signal crosses the lower threshold of the Schmitt trigger in the negative-going direction, the rear edge of 50 the gate signal 113 automatically re-closes the switch Sg, causing the capacitors to discharge by placing the voltage UQ atthe output line 141 while the electron beam returns to its starting point. Atthe same time, the duration of the gate signal 113 is counted out in the counter 13 with the aid of the clock pulses generated in the clock pulse generator 14 and the value of the count is transferred to the microprocessor via the data bus lines 118, i.e. the microprocessor 114 delivers a digital value equal to the difference between the set-point 55 value and the actual value of the traversing time. This difference value is converted into an analog signal in the converter 16, i.e. into the signal UE which causes a change in the current I and thus causes a change in the traversing time of the next sawtooth waveform. When the actual and nominal (set-point) values are found to be equal, the digital value thereof is stored in an intermediate memory 116.

A prerequisite for the fine adjustment described above is that the actual value of the traversing time is at 60 'east roughly equal to the set-point value atthe beginning of the comparison. This preliminary coarse setting is obtained in that the microprocessor selects a combination of capacitors so that the joint capacitance, togetherwith an average control voltage UE, produces a traversing time which lies near the desired nominal value. The microprocessor obtains this combination by consulting a table which correlates the externally supplied settings with the appropriate combination of capacitors. A corresponding control signal then closes 65 the correct switches St - S8 and the digital value of the coarse setting is passed over the data bus 118 into an

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intermediate memory 117 where it is stored.

The release and loading processes in the intermediate memories 116 and 117 and in the counter 13 are initiated by signals from the decoder 120 which is connected to the control bus 119 and which is controlled by the microprocessor 114.

5 The above referred-to table within the microprocessor is generated by a suitable program and may be checked for accuracy from time to time in automatic fashion. For example, after the oscilloscope is turned on, the microprocessor may select an average value for the voltage UE and then connect the capacitors C-i -C8 sequentially while constructing a table of coarse, i.e. approximate values for the traversing time of the sawtooth voltage, i.e. these values are stored temporarily. Thereafter, the nominal value of the traversing 10 time selected on the external keyboard 17 is compared with the various values stored in the microprocessor and the closest approximate value is chosen by closing the appropriate set of switches via the intermediate memory 117.

This coarse adjustment is followed by the fine adjustment already described above. This process may take place cyclically in several stages, i.e. by successive approximation in, for example, eight steps, and may be 15 repeated from time to time so as to insure the long-term constancy of the selected traversing time. However, preferably, the desired value of the traversing time tH is determined as follows: After the coarse adjustment, the microprocessor 114 places on the input line of the converter 16 a digital signal having the hexadecimal value 0 and stores the resulting traversing timetHi atthe output of the counter 13; this value represents the traversing time which occurs for an adjustment current of value 0. Subsequently, this process is repeated for 20 a signal with the hexadecimal value FF=255 and the resulting traversing time tH2 is also stored; this value represents the traversing time for the maximum adjustment current I. Using the values tm and tH2 and the pre-selected nominal time tH, the microprocessor 114 then obtains the digital value DW which most closely approximates the desired traversing timetH on the basis of the following relation:

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DW = 255 (1 - tH/tm) - (tH/tH2 - tH/tHi) (1)

This value is transferred via the intermediate memory 116 to the converter 16 which generates a voltage 30 UE that is used to adjust the current I in such a way as to obtain the desired traversing time tH.

The derivation of the formula (1) is not a prerequisite for the understanding of the invention but the following considerations are offered.

Assuming tH = k- C/l,

where k is a constant, C is the capacitance to be charged and I is the constant current set by the resistor R0, 35 then if

I = Ue/R0 and UE = a-DW + b (a and b = constants)

and using the expressions a1 = a/(K-RC) b, = b/(K-RC)

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one obtains

50 for DW — 0 : t^i — 1 /t>i; bi — 1/tm and for DW = FF: tH2 = 1/(a,FF + 1/tm); a, = (1/tH2-1/tHi)/FF

55 When the values of a! and bi are substituted in these relations, formula (1) is obtained.

Figure 3 illustrates details of the circuitry, especially the construction of the electronic switches St -S9 of the sawtooth generator shown in Figure 2. These switches are constructed of per se known transistor circuits as shown. Of the switches St -S8, only the first two, S-i and S2 are shown in Figure 3 and each of these is seen to be built up of an amplifier circuit consisting, for S-,, of the transistors T-i and T,' and a voltage divider made 60 up of resistors Ri and R/.The base of the transistorT-,' is connected via a resistor RE1 and the line 142 to the intermediate memory 117 shown in Figure 2. All switches Si - S3 are of identical construction and each is connected, in the manner shown, to a respective capacitor, Cv C2 etc, the other side of which is connected to the output line 141. The function of, for example, the switch S-i is that the transistorT-,' becomes conductive when its base receives a voltage from the intermediate memory 117 via the control line 142, causing the 65 transistor ^ to conduct and to apply the voltage U0to the plate of the respective capacitor Ci connected to its

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collector. The operational amplifier 115 and the resistor R0 are connected to the output line 141 via a transistor T0. The transistor T0 serves only to minimize the effect of the constant current I on the operational amplifier 115. The switch Sg which applies the voltage UDtothe line 141 and hence to the upper plates of the capacitors consists basically of the transistors Tg and T9' and the resistors R9 and R9' and it is connected to 5 the output of the flipflop 121 via the parallel connection of a resistor 150 and a capacitor 151. As already shown in Figures 1 and 2, the set-input of the flipflop 121 receives the trigger pulse and the reset input of the flipflop 121 is connected to the output of the Schmitt trigger circuit 12. At the occurrence of a gate signal 113 from the flipflop 121, the transistor T9' is rendered conductive causing the transistor T9 to block whereas, when the gate signal 113 ends, the transistor T9' blocks and the transistor Tg conducts, placing the voltage UD 10 on the output line 141.

The circuit shown in Figure 3 also contains additional elements, not contained in the circuit of Figure 2 and illustrated in dashed lines. These additional elements improve the effectiveness of the previously described circuit but elements not essential forthe functioning of the circuit, e.g. resistors and capacitors, have been omitted from the figure for reasons of clarity.

15 The additional elements in Figure 3 include a Zener diode Z, a resistor Ri0, and a transistor Ti0 which, together with the switch S9, form a control loop that defines the base potential of the sawtooth voltage. Without such a control loop, the base voltages of the various sawtooth wave forms would differ due to the different conducting impedances of the transistors T-, -T8. This situation is illustrated in Figure 4a which shows that the base potential 155 of the switch Sn and the base potential 156 of the switch S2are both 20 smaller than the voltage U0. Figure 4b illustrates the sawtooth waveform when the additional control circuit of Figure 3 is active. The Zener diode must be so chosen as to become conductive at a voltage -UZ<U0, i.e., in the present example, at a voltage Uz = 65 V, for example.

Figure 3 also shows that the base of the transistor T10 receives the voltage present atthe junction of the Zener diode Zand the current-limiting resistor Rno, permitting the transistor Tno to control the transistor Tg, 25 i.e. the firing voltage of the Zener diode is stabilized in that the transistor Tg blocks when the voltage on the line 141 becomes too large while it conducts when the voltage UQ is too small.

The remaining additional elements shown dashed in Figure 3 include the transistor T11( a flip flop 122, a monostable multivibrator 123 and a transistor T12 whose function it is to minimize the return time of the sawtooth voltage, i.e. the time during which the electron beam returns to its starting point. This circuitry is a 30 refinement of that shown in Figure 2 for the sawtooth generator 11. The return time will be very short if the resistance of the resistor Rg is relatively small, e.g. 50 Ohm, permitting the charge of the capacitor or capacitors then connected in circuit to drain rapidly and the potential on the line 141 to return very rapidly to the value UQ after the transistor Tg becomes conductive. However, if the constant current I were also permitted to flow through the transistor Tg at this time, the total current would be quite high and might 35 damage the transistor. Forthis reason, the constant current I is interrupted atthe start of the fly-back, i.e. the beginning of the trailing portion of the sawtooth waveform, henceforth referred to as the return time. This is accomplished by passing the pulse from the Schmitt trigger which occurs when the sawtooth voltage crosses the lower threshold to the set-input S of the flipflop 122 via the line 158, causing the transistor T12 to conduct, thereby placing the control voltage UE atthe input 140 of the operational amplifier 115 at ground 40 potential with the result that the operational amplifier 115 generates a constant output current of approximately zero value. After the Zener threshold Uz is exceeded, the voltage drop across the resistor R10, which is amplified by the transistor T11f passes through the line 159 to the monostable multivibrator 123 which generates a corresponding short reset pulse forthe reset input R of the flipflop 122 that returns the latter to its original state in which the transistorT^ is blocked and the original constant current I is 45 re-established by the operational amplifier 115 at a value determined by the intermediate memory 116 in Figure 2 and by the converter 16. The effect of the additional circuitry is thus an interruption of the constant current I following the termination of the gate signal 113 until such time as the voltage on the output line 141 is equal to that defined by the Zener diode Z.

The circuitry according to the present invention, as described above, is particularly suitable for 50 oscilloscope apparatus which already includes a microprocessor for other reasons, for example for processing the measured signals. The circuit according to the invention may be used with particular advantage in multi-trace oscilloscopes in which each channel requires its own sawtooth waveform risetime, i.e. its own X-deflection rate. For such a case, the microprocessor automatically calculates the required coarse and fine values for the traversing times and stores them. When the X-deflection plates are switched 55 over to another channel, the microprocessor automatically places these new values forthe traversing time in the intermediate memories 116 and 117. New calibrations of the different traversing times are not required.

If the circuit according to the invention is used in ultrasonictesting equipment, the input keyboard 17 may be used to enter data regarding the desired display width (e.g. 0-200 mm) as well as the kind of material to be tested (e.g. steel) and data related to the type of testing element or testing head (e.g. a delay distance of 4 60 mm). In other words, the slope of the sawtooth waveform is not entered in terms of the time of traversal of the electron beam across the display but rather as the distance of travel of the ultrasonic beam in the test object (for example 0-200 mm). The propagation of the ultrasonic beam is a function of the velocity of propagation of sound in the test object and this velocity in turn relates the depth of penetration of the ultrasonic beam to the elapsed time. The data to be entered on the keyboard is thus the desired depth of 65 inspection within the test object and the applicable velocity of propagation of ultrasonic energy. From these

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relations, it is possible to derive an appropriate electron beam traversing time, i.e. a time during which the test signal passes through the desired testing area. However, consideration must be given to the fact that the ultrasonic signal must first cover the distance between the piezoelectric transducer element in which it is generated and the beginning of the test region within the test object; this distance is also entered into the 5 keyboard. The delay (pretravel) distance is actually composed of the distance between the piezoelectric 5

element and the surface of the probe and a second distance defined by the depth at which the region to be tested begins. Accordingly, the onset of the X-deflection must be delayed by a given amount of time, called the trigger delay time, as a function of the time required forthe ultrasonic beam to traverse the delay distance. This time delay is produced by a trigger delay circuit.

10 Figure 5 illustrates a block diagram of the circuit for a portable ultrasonic test instrument. As already 10

described, the microprocessor 114 is connected to the keyboard 17 via the multi-conductor data bus 118 and the control bus 119. A sweep generator 124 is also connected to the data bus 118 and the control bus 119;

this trigger generator includes the sawtooth generator 11, the intermediate memories 116,117, the decoder 120, the converter 16, the Schmitt trigger 12 and the counter 13. The trigger generator is connected to the 15 X-deflection plates of the CRT 112 via a horizontal amplifier 110. Atrigger delay circuit 125 is connected to 15 the data bus 118 and the control but 119 and is coupled to the sweep generator 124 via a line 100 which serves to transmit the delayed trigger pulse to the flip flop 121 in the sweep generator so as to cause the start of the sawtooth waveform.

As the electron beam is to be made visible only during its traversal time tH but is to remain dark during the 20 flyback, a control unit 126, acting through an amplifier 164 inhibits the electron beam during that time. The 20 control unit 126 receives a trigger signal for beam release from the trigger generator 124 via a line 160.

Additional circuit elements 127, to be discussed below, may also be connected to the microprocessor 114. The clock pulse generator 14 is connected to the trigger generator 124, the trigger delay circuit 125 and the microprocessor 114 via the line 162.

25 The ultrasonic driving signal is generated by means of a transmitter 128 upon the occurrence of a pulse 25 received from the microprocessor 114 on the line 161. The transmitter 128 excites the transducer 129 which emits an ultrasonic beam. Any returning echo signal is detected in the transducer 129 and converted into electrical signal which are amplified in the amplifier 131 which applies them to the Y-deflection plates of the CRT 112, causing a vertical deflection of the electron beam due to the occurence of an echo. For example, if it 30 is desired to test for any defects in a steel object at a depth of between 20 and 50 mm, these values are 30

entered into the data keyboard 17 togetherwith the velocity of sound in steel and the delay distance mandated by the type of testing head used. The microprocessor 114 then calculates the trigger delay time,

i.e. the time during which the switch S9 of the sawtooth generator (Figure 2) is to remain closed. This time corresponds to the delay distance of the ultrasonic beam in the test object to a depth of 20 mm; when this 35 distance has been traversed, the sawtooth waveform for X-deflection of the electron beam should begin. The 35 required traversing time of the sawtooth waveform is also calculated by the microprocessor 114. These times are expressed in the form of quantities of clock pulses on the basis of a clock frequency f0 which depends on the required resolution or display accuracy. For example, if a resolution of 0.3 mm is required to defect faults in a steel test object, i.e. if faults of this magnitude must be reliably detected, then the clock 40 frequency needed with ultrasonic signal whose longitudinal velocity of propagation is csteei (applicable for 40 normal probes) is given by:

fo = csteei/2(0.3) or approx. 10 MHz.

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The overall trigger delay time time tKv is the sum of the pretravel (delay) time tsv in the probe and the delay time t"M within the test object (corresponding in the present example to a distance of penetration of 20 mm). The delay time tSv in the probe may be calculated from the probe delay distance Sv divided by the ultrasonic propagation speed in the probe (cv) while the delay time tM in the test object may be calculated by dividing the path SM within the test object (20 mm) by the ultrasonic propagation velocity CM in the test object. The quantity of pulses corresponding to the correct trigger delay time is then given by:

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*kv '

2f,

5v SM

Cv Civl

(2)

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The quantity of pulses corresponding to the display width, i.e. the traversing time of the sawtooth waveform, is given by

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IMbb = 2f0 (Sbb/Cm)»

where Sbb is the depth range in the test object, e.g. 30 mm. The pulse count Nkv passes from the microprocessor 114 to the trigger delay circuit 125 via the data bus 118 while the pulse count NBb is applied 65 to the trigger generator 124. Subsequently, the microprocessor 114 generates a trigger pulse on the line 161, 65

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whereafter the transmitter 128 starts to send out a signal. Atthe same time, the trigger delay circuit 125 is released and starts to count down the pulse count TKv which defines the trigger delay time. After the expiration of the trigger delay time, the trigger signal passes from the trigger delay circuit 125 to the sweep generator 124 via the line 100 where it causes the opening of the switch S9 and the onset of the sawtooth 5 voltage in the manner described with the aid of Figure 2. The necessary clock pulses are provided by clock pulse generator 14 over the line 162. Simultaneously with the onset of the sawtooth voltage, the electron beam current is enabled by the amplifier 164 which acts on the cathode assembly of the CRT 112; this event is produced by the control circuit 126 on the basis of a signal received overthe line 160. Any echo signal received during the traversing time tH of the electron beam results in a vertical (Y) deflection of the electron 10 beam and constitutes a fault indication in the test object. Figure 5 includes provision for a data recording device, e.g. a cassette recorder 166 which is connected to the data bus 118 and the control bus 119 of the microprocessor 114 and serves, e.g. for recording the ultrasonic test results.

Figures 6a and 6b illustrate how the pulse count number NKv, computed according to the formula (2), may be corrected by an improved embodiment of the invention, so as to obtain the best possible pictorial 15 representation. This improvement is based on thefollowing considerations. The normal starting pointfor the electron beam of an oscilloscopic display is a point 170, usually atthe left margin of the cathode ray display tube. The electron beam occupies this point when the horizontal deflection voltage is UKst and has a value which is usually smaller than the base line voltage of 65 Volts of the sawtooth waveform. This situation is depicted in Figures 6a and 6b. After expiration of the trigger delay time tKv» defined by the pulse count 20 number NKv» the sawtooth voltage is released. The time A tKsT which elapses until the electron beam has reached the point 170 depends on the slope of the sawtooth waveform. As shown in Figure 6b, if the slope is shallow, the actual image starting point 171 is reached at a latertimethan would be the case with a steep slope. Accordingly, it is suitable to delay the onset of the sawtooth voltage in dependence on the slope of the waveform. The delay of the trigger starting point can be derived approximately from the formula

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At|<sT ~ a . tee

30 where a is a constant which depends on the desired image starting point and tBB is equal to the traversing timetH of the electron beam and corresponds to the time during which it is possible to observe the beam on the screen in its motion from left to right, for example. The resulting corrected pulse count number is then

35 N'kv = NKV — aNeB-

Figure 7 is a block diagram of a trigger delay circuit 125. The pulse count number NKv which is calculated by the microprocessor 114 on the basis of the data entered into the keyboard 17 is loaded into a register 133 40 and passes over a first input line 170 to a binary counter 134. The second input 171 of the binary counter 134 is connected to the output of an AND-gate 128 through a switch S10-The inputs of the AND gate 128 are connected, respectively, to the output of the clock pulse generator 14 and an output of a flip-flop 135. A further flip-flop 174 actuates the switch S10 between two positions A and B; in the position A, the binary counter 134 receives the pulsetrain with frequency f0 whereas, in the position B,the counter 134 receives a 45 pulsetrain with frequency fo/10 after division in the circuit element 175. This selection makes possible a change of the effective image resolution, as previously described. If the trigger pulse generated by the microprocessor 114 on the output line 161 reaches the flip-flop 135, the AND-gate 128 is open and the clock pulses pass from the clock pulse generator 14 to the binary counter 134. As a result, the triggering delay number NKv< which is stored in the counter 134 is counted down at the frequency fQ or fo/10, depending on 50 the position of the switch S10. Atthe conclusion of the count, the counter output 172 generates a pulse which passes overthe line 100 (Figure 5) to the trigger generator 124 and constitutes the onset of the gate signal 113 which opens the switch S9 (Figure 2) that releases the sawtooth waveform.

It is a substantial advantage of the present invention that the above described circuits make possible the calibration of the imaging area of the CRT in terms of units of length. This calibration is based on the 55 provision of suitable traversing times of the beam, i.e. rise/fall times of the leading ramp of the sawtooth waveform which serves as the horizontal deflection voltage (time base voltage). A direct calibration of this kind has not heretofore been possible in testing instruments because the known instruments did not possess the necessary long-term stability of timing components so that the agreement between the selected values of the traversing times and the actual values differed in unpredictable ways and could become substantially 60 different overthe course of time. In order to counteract these defects in the known apparatus, it has become customary to re-calibrate the CRT displays by conducting tests on test objects of known dimensions. This kind of re-calibration, which is relatively time-consuming and which must be repeated from time to time can now be avoided due to the features of the present invention. According to the invention, any imaging region may be pre-selected on the keyboard and will be maintained exactly by the continuous comparison of the 65 nominal value and the actual value of the effective beam traversing time.

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As previously described, the invention permits the representation of a particular range within the test object by causing the triggering of the sawtooth signal, i.e. the start of the CRT image field, after a given holding or trigger delay time has expired and it further permits a selection of the length of the imaging region on the basis of the sawtooth rise/fall time, i.e. the beam traversing time.

5 It may be desirable to provide for an automatic indication of the occurrence of echo signals which are produced by faults within a given depth range in the test object. Such automatic indication is also possible according to a further feature of the invention to be described below. This feature is a so-called time and amplitude gate which defines and displays a "gate-bar" on the CRT screeen. Any echo signal whose amplitude is greater than the vertical position of a bar display and which occurs within its horizontal limits, 10 i.e. it width, is automatically recognized and may serve to initiate an alarm or other action. The vertical and horizontal positions of this gate-bar and its width should, advantageously, be selectable. The gate-bar may be displayed by the electron beam between successive displays of the other signal data on the screen.

Figure 8 again illustrates an ultrasonic testing instrument which includes a transmitter 21 for producing the sound-generating drive signal for the transducer 22, an amplifier 24 for receiving echo signals detected by 15 the transducer 22 and associated elements to be described. The echo signals received from the test object 23 are objected into electrical pulses and amplified by the amplifier 24; they pass over the line 230 to the vertical (Y) deflection plates of the CRT 25 to cause the vertical deflection of the electron beam in known manner. The horizontal timing signal, i.e. the sawtooth voltage, is produced, in the manner already described, by the trigger generator 26 and corresponds to the range of interest within the test object. The necessary holding 20 time, i.e. the time which must elapse between the onset of the ultrasonic signal and the release of the sawtooth waveform, is determined in the trigger delay circuit 27 as also already described. The microprocessor 28 passes the corresponding trigger pulse overthe line 232 to the transmitter 21 and to the trigger delay circuit 27. In this illustration, the data and control buses for transmitting the data and pulse count numbers among the various circuits have been omitted for clarity. During the traversing time of the 25 beam, the trigger generator 26 places a signal 234 on the line 233 which serves to enable the cathode assembly of the CRT and provides for the display of signals thereon.

The horizontal distance SA defining the start of the gate-bar (time gate) and its width SB are produced by the microprocessor 28 whose output line 231 is connected to a register 29 which is followed by a counter 210 connected to a flip-flop 211.

30 Let it be assumed that the various data items relating to the characteristics of the testing head, as well as the delay distance Sv of the ultrasonic signal in the probe, the velocity of sound Cv in the probe and the velocity of sound CM in the test object object are all known and are available as digitial values within the assigned memories of the microprocessor 28. If the operator now selects the desired gate-bar constants, i.e. the starting position SA, the width SB and the vertical position of the gate-bar (amplitude) by entering these 35 data as e.g. lengths in millimeters or percent of CRT height, the microprocessor 28 computes the corresponding internal data items on the basis of a stored program. These internal data items are previously referred-to pulse count numbers of the type N, in this case a number NMA which defines the onset position of the gate-bar and NMB which defines the width of the gate-bar. The clock frequency f0 depends on the desired resolution, i.e. on the precision required in the image. As already discussed in connection with the overall 40 image width, an image resolution of 0.3 mm in a test object made of steel in which the speed of propagation of longitudinal ultrasonic waves is csteei requires a clock frequency given by f0 cs,ee|/2(0.3mm)

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or approximately 10 MHz.

If tA is the time up to the occurrence of the gate bar, i.e. the time which is the sum of the delay times in the 50 probe and the test object, then the pulse count number defining the horizontal position of the gate bar is given by

Nma — 2f0 (Sy/Cv + Ca/Cm)

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where Sv is the delay distance in the probe;

Cv is the velocity of sound in the probe;

SA is the delay distance in the test object; 60 CM is the velocity of sound in the test object.

The pulse count number defining the bar width is given by

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Nmb = 2f0 (Sb/Civj)

where SB is the width of the bar in units of length.

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The calculated pulse number NMa is loaded into the register 29 via the line 231 and is passed into the counter 210. Subsequently, the pulse number NMB is also transferred to the register 29 where it stands ready to be passed to the counter 210. If the line 232 now receives a new trigger pulse from the microprocessor, this pulse opens the input 233, causing the contents of the counter 210 to be counted down by the signal train 10 from the clock 213, at the frequency fD. When the count is complete the counter output 234 carries a first pulse li which sets the flip-flop 211.

The pulse !•, is also passed to the load inputs 235 of the counter 210 and enables them for receiving the pulse number NMB which is immediately counted down, whereafter the counter output 234 carries a pulse l2, which resets the flip-flop 211, causing a square pulse 237 to be generated atthe output 236 of the flip-flop 15 211. The ultrasonic signal and the gate bar are displayed alternately on the screen by the switches St and S2. Forthe position of these switches as shown in Figure 8 (full lines), the ultrasonic signal is displayed and passes through the line 230 to the Y-deflection plates of the CRT 25. At the same time, this signal passes to the comparator circuit 216 whose other input is connected to the converter 214 through the switch S-i and the line 238. The converter 214 transforms the digital value of the bar height into an analog voltage. Figure 8 also 20 shows that the two inputs of an AND-gate 217 are connected, respectively, to the output line 240 of the comparator 216 and the line 239 leading to the switch S2. If the comparator 216 determines that the amplitude of the ultrasonic signal on line 230 is larger than the height (threshold) of the bar represented by a signal on line 238, it delivers a square pulse and the AND-age 217 is open as long as the square pulse from the flip-flop 211 is present online 236, ie. when the echo signal to be represented is larger than the bar height 25 and falls within the width of the gate bar. In this case, the flip-flop 218 connected to the AND-gate 217 is switched and applies a signal to the line 241 which may be used to trigger an alarm, e.g. a horn or buzzer. The display of the ultrasonic signal and the triggering or the alarm occur atthe same time, provided that the echo signal is largerthan the set height and falls within the width limits. The flip-flop 218 is reset by a signal from the microprocessor received on the line 242. The above-described circuit may be used as a peak 30 detector circuit by causing the microprocessor to follow a program of gradually increasing the threshold until the output of the AND-gate 217 no longer indicates the existence of an echo signal; i.e., the microprocessor 28 automatically increases the gate threshold fed to the converter 214 in step-wise fashion while the comparator 216 performs successive comparisons so that the maximum value of the echo signal may be determined.

35 If, however, the switches Sn and S2 are in the position shown in dashed lines in Figure 8, the CRT displays the gate-bar. This is accomplished in that the microprocessor applies a trigger signal to the counter 210 via the line 243 and also to the trigger generator 26. The D-A converter 214 applies a bar height signal to the Y-deflection plates of the CRT, thereby positioning the bar atthe correct height on the screen while the square pulses 237 on the output line 236 of the flip-flop 211 which defines the horizontal position of the 40 gate-bar is passed through the switch S2to the cathode beam control electrode of the CRT (Z-input) to enable the beam current which makes the gate bar visible on the screen.

Figure 9 is a timing diagram which illustrates the timing of the various signals and events. Figure 9a shows three successive trigger pulses. The ultrasonic display occurs between the first and second trigger pulses. If necessary, the microprocessor calculates the new pulse count number forthe gate start, NMa and the 45 number NMB for the gate width. These numbers are loaded into the register 29 followed by the monitoring and indicating of the occurrence of an echo signal within the defined gate bar with an amplitude exceeding the vertical position of the bar. After the switches St and S2 have switched, the gate bar is displayed between the second and third trigger pulses. In the next cycle, the ultrasonic echo signal is displayed again a.s.o. If a second gate bar is to be displayed, it has been found to be suitable to permit an intervening display of an 50 echo signal to maintain adequate brightness of the echo signal. Due to the fact that the individual sequential displays follow one another with great rapidity, an observer perceives all events simultaneously.

Figure 9b shows the signal applied to the vertical (Y) deflection plates. Between the first and second trigger pulse the figure shows the ultrasonic signal which may be received during a test while the voltage corresponding to the bar height is shown between trigger pulses two and three. Figure 9c shows the 55 horizontal deflection voltage and it will be seen that, after the first trigger pulse, a holding timetBAis permitted to elapse by the trigger delay circuit 27 whereafter the trigger generator 26 is actuated and generates the sawtooth waveform during the time tBB. The beam-enabling voltage applied to the Z-input of the CRT is generated only during the time tbb and the waveform of the echo signal is visible only during that time. Figure 9 shows this Z-control pulse. Figure 9e illustrates the rectangular signal 237 which occurs atthe 60 output 236 of the flip-flop 211 and which is released after a time tMA for a period equal to the width of the gate bar. This signal is applied to the AND gate 217 and causes the switchover of the flip-flop 216 if the comparator 216 senses that the gate threshold is exceeded, permitting the activation of an alarm or recording device via line 241.

While the gate bar is being displayed, i.e. during the time period between the trigger pulses two and three, 65 the vertical (Y) deflection plates of the CRT receive the bar height signal supplied by the converter 214 which

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is shown in Figure 9b, while the horizontal (X) deflection plates receive the sawtooth voltage supplied by the trigger generator 26 which has the same traversing (rise) time tBN as the traversing time tBB of the imaging beam. These relations are shown in Figure 9c. During the time Imb in the diagram of Figure 9d, the screen displays the gate bar because of the presence of theZ-control signal from the flip-flop 211, shown in Figure 5 9e. The time t'MA shown in Figure 9e indicates the time span between the onset of the sawtooth voltage and the triggering of the signal for representing the gate bar, i.e. the onset of the gatebar display. Accordingly, the pulse count number for the start of the bar display is

10 N'ma— NMA- NBA

The advantage of advancing the gate bar start by the time tBA resides in the fact that more time is available for further processing and that the next transmitter trigger pulse can be released sooner.

15 The gate bar trigger pulse occurring on line 232 need not actuate the transmitter 21 because ultrasonic echo signals received during that time are not processed anyway.

Figure 10 shows a preferred circuit for generating the pulses l-i and l2 related, respectively, to the onset and termination of the gate bar. As in Figure 8, the microprocessor 28 is connected via the line 231 to the register 29 which, in turn, is connected to the counter 210. The register 29 may be embodied, for example, as a 20 counter of the commercial type SN 74C374; the counter 210 may be a binary down-counting counter, composed, for example, of two commercial counters of the type SN 74191, connected in series.

One input of an AND-gate 220- is connected to a clock generator 213 and receives a signal train of frequency fQ while the other input is coupled to the output of a flip-flop 221. Depending on the position of the switch S3, either the full frequency fQ or the frequency f0/10 is applied to the counter 210 via line 244. The 25 switch S3 is controlled by a flip-flop 223. The microprocessor 28 applies control signals to various points, i.e. to the control input 245 of the register, the input 246 of an OR-gate 219 which controls the input 247 of the counter 210, to the control inputs 248 and 249 of the flip-flop 221 and to the control inputs 250 and 251 of the flip-flop 223.

A control signal at the control input 245 of the register 29 causes the pulse count number NMa» related to 30 the onset of the gate bar, to be loaded into the register 29. Subsequently, the control signal atthe input 246 of the OR-gate 219 causes loading of the pulse count number NMA in the counter 210. Finally, the pulse count number NMB, related to the width of the gate bar, is loaded into the register. This number is available for processing atthe up-count inputs 248 of the counter 210.

A control signal applied by the microprocessor to the input 250 or 251 of the flip-flop 223 determines 35 whether the switch S3 passes the full frequency fD or the diminished frequency fo/10 to the counter 210.

The counting process is initiated by a trigger signal supplied by the microprocessor to the input 248 of the flip-flop 221. The content of the counter 210, i.e., the pulse count number NMA, related to the onset of the gate bar, is counted down. When the count has reached zero, a pulse on line 234 is passed to the flip-flop 211 (Figure 8) and also to the other input 252 of the OR-gate 219, so that the pulse number NMB, related to the 40 gate width, is transferred to the counter 210. The clock pulses arriving on line 244 are used to count this number down as well and when the count reaches zero, the pulse l2 signifies the termination of the gate bar.

It is possible to perform the counting of the numbers related to onset and the width of the gate bar with different frequencies. That will be necessary if one of these numbers exceeds the capacity of the counter 210. One input of the flip-flop 223 which actuates the switch S3 is connected to the output of an AND-gate 224 45 whose one input is connected to the output of a further flip-flop 225 that is set by a pulse arriving from the microprocesor on line 253 and reset on line 254. The other input of the AND-gate 224 is connected via the line 255 to the output line 234 of the counter 210. In this way, after the time before the onset of the gate bar has expired, the pulse h on the line 255 can be used to flip the switch S3 if an appropriate control signal is present at the set-input 253 of the flip-flop 225.

50 One significant advantage of the above described circuit is that the dimensions of the gate bar can be entered directly on the keyboard in units or length (mm or inch) and will cause the correct positioning of the gate bar on the screen. All the relevant data and parameters, such as the delay distances, the speed of sound in the testing head and in the test object etc. are taken into account by the microprocessor during the calculation of the corresponding pulse numbers. Accordingly, it is no longer necessary to set the parameters 55 of the gate bar with analog devices, e.g. potentiometers, while the final calibration must be made manually.

Figure 11 is a block diagram of another embodiment of the ultrasonic testing instrument shown in Figure 5, including a number of additional elements. The microprocessor 31 of Figure 11 includes a computer unit 32 and several memories, i.e. a ROM 33, a RAM 34 and a Random Access Read Out Memory 35 connected to an internal bus 36. The microprocessor 31 is connected to the external system of buses via an Input/Output 60 circuit 37. The external buses include an 8-line data bus 340, an 8-line control bus 341 and additional lines 342 and 343 which will be further explained below. The microprocessor is preferably of the type Z80, for example as manufactured by MOSTEK and marketed under the designation Z80 Microprocessor. The circuit of Figure 11 also includes again a transmitter 315 for producing the ultrasonic drive signal, the probe 316 for transmitting the ultrasonic signal into a test object 318, as well as for receiving the echo signals which pass 65 to an amplifier 317. As already mentioned, the transmitter 315 is activated by receipt of a trigger pulse on the

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line 344; it sends a transmission pulse to the probe 316 via the line 345, causing the transmission of ultrasonic energy into the test object 318. The transmission trigger pulse is produced in the microprocessor 31 and passes to the trigger delay circuit 38 via the I/O circuit 37 and the data and control buses 340,341. After a delay time, the circuit 38 produces the transmission trigger pulse. The ultrasonic pulse transmitted into the 5 test object may encounter structural faults which cause echoes that are reflected back to the probe 316 where the echoes are converted to electrical signals which are amplified in the receiver/amplifier 317. The amplified echo signal is provided to the switch S which, when in position A, transmits the signal to the vertical (Y) deflection plates of the CRT. The horizontal (X) deflection plates of the CRT320 provide the time base of the display and are connected to the output of an amplifier 321 which is driven by a trigger generator 39. A 10 control circuit 310 provides the necessary beam control signal (Z-control) to a Z-axis amplifier 322; this signal is provided during the time during which the sawtooth voltage occurs. The microprocessor is also connected to receive input from a keyboard 313 which serves to enter desired operating parameters and a recording device, e.g. a tape recorder 314 for storing the test data. Still further connected to the microprocessor is a screenwriting circuit 311 which can feed text signals to the CRT when the switch S is in 15 the position B and a gate-circuits 312 that generates the aforementioned gate-bar. A clock 323 delivers timing pulses to the trigger delay circuit 38 and to the gate circuit 312. The various lateral connections among the elements 38,39,310,311 and 312 are designated 352-355. The switch S is controlled by the control unit 310 overthe line 356.

Figure 12 is a front elevational view of an ultrasonic testing instrument according to the invention which 20 houses the circuitry of Figure 11. The front panel of the instrument includes a CRT 324 and four groups of data entry devices T-i - T4. Group T3 also includes a rotary knob 325 and a multiplier button 326. The various key switches are of commercial origin and are available, for example, from the firm Datanetics/Knitter. These key switches must be equipped with suitable coding circuits, for example matrix-type coding circuits so that an application of a given key produces an acceptable binary datum forthe microprocessor. 25 The keyboard group Ti includes three keysT, A and A' which provide the basic mode of representation of the instrument. Depression of the keyT causes the instrument to be usable in the manner of a data terminal, i.e., printed text is placed on the screen 324 in a manner yet to be described. Actuation of the key A causes the well-known A-representation which provides forthe display of echo signals from faults in the test object and actuation of the key A' provides for display of the A-type with simultaneous display of a line of text. The 30 key group T2 includes four keys related to basic functions, namely a key BS for screen data, a key PKfor probes data, a key MA for materials data and a key MO for gate data. Actuation of any of these keys provides data entry access to the respective memories in the microprocessor 31. The key group T2 also includes the keys C and C' which can be used to move a cursor vertically (using key C) or horizontally (using key C'). If the cursor is placed on particular line or column in the display, the keys in group T3 provide access to the 35 memory location related to the cursor position.

The key group T4 consists of two special function keys, a key AS, which, when actuated, provides for storage of the A-image representation and a key LZ which permits measurement of the propagation time of the ultrasonic signal.

Figure 13 is an example of the text data which may be displayed on the screen upon actuation of the keyT 40 in the key group T] and actuation of the key MO in the key group T2. The data displayed are those which had previously been entered into memory by the keys in the group T3. The display includes a movable cursor, an unchanging explanatory text, variable data taken from memory and changeable by application of the appropriate keys of group T3 and suitable dimensions.

If the key MO is actuated, the test and the dimensions are read out of the ROM 33 into the appropriate 45 section of the RAM 35. The changeable parts of the display are taken from the RAM 34 and placed in the corresponding sections of the Read-out RAM 35. By placing the cursor atthe proper location with the aid of keys C and C' and actuating the keys in the group T3, the stored data may be altered at will and is then displayed on the screen. The complete text is continuously displayed until a different set of keys is actuated.

When the entry of the operating data is complete, i.e., when the various parameters relating to the CRT, the 50 probe (delay distance, velocity of sound etc), the test object (velocity of sound, etc.) and the gate-bar (onset, width, threshold, alarm and peak detector) have been entered by use of the various keys in group T2, the key A is depressed, whereupon the microprocessor 31 begins to compute from these data the required count numbers N for the trigger delay circuit 38, the trigger generator 39 and the gate 312 in the manner already described above.

55 Subsequently, the screen displays the A-image corresponding to the workpiece, i.e. the echoes reflected from inhomogeneities within the workpiece and within the selected depth range. The adjustments required to account for the various characteristics of the probe, the material of the workpiece and the characteristics of the CRT are all automatically taken into consideration so that no further calibration is required. During this display, the switch S of Figure 11 is connected to the contact A.

60 As already explained, when the holding time tBA computed by the microprocessor 31 has expired (see Figure 9), the trigger delay circuit 38 sends a pulse overthe line 352 (Figure 11) which triggers the generation of the sawtooth voltage with a forward trace sweep time tBB also as computed by the microprocessor. The sawtooth voltage is applied to the horizontal (X) deflection plates of the cathode ray tube 320. The sawtooth voltage is also used to generate the intensity control signal via the line 353 by causing the control unit 310 to 65 produce a rectangular pulse for the duration of the sweep time of the sawtooth, which pulse is applied to the

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Z-control inputs of the CRT 320.

If the key A' is depressed instead of the key A, i.e., if it is desired to display the signal and the text simultaneously, a line of text appears on the screen in addition to the echo signals, namely the line to which the cursor points. This condition is shown in Figure 15. In this mode of display, the switch S of Figure 11 5 alternates between the contacts A and B. In the position A, in which it resides for approx. 18 ms, the screen 5 depicts the echo signal one or more times. In the position B, in which the switch resides for approx. 2 ms, the line of text is displayed. Due to the relatively short dwell times and the rapid repetition rate, the observer perceives a composite display.

Figure 15 is a representation of a display including the gate bar in the position it occupies when the 10 following keys are actuated: in the key group T2 the key MO is pushed causing the display of the "gate" 10

function to appear as shown in Figure 13. The cursor is then positioned to the line marked "display" and the key marked "YES" in the key group T3 turns on the gate. When the key A or A' is pressed, the gate bar appears. In the case of actuation of key A', the screen shows the ultrasonic echo for 18 ms and subsequently the gate bar and line of text of approx. 2 ms.

15 Figure 14 is a block diagram of a portion of a circuitsimilarto that of Figure 11 but including some 15

additions. The additions comprise a transit time meter 327, an A-image converter 328 and an interface unit 329 for connecting the instrument to an external processing device, not shown. In this manner, the ultrasonic pattern can be presented additionally to the A-image converter 328 where it is converted into digital values which can be either stored in the RAM 34 of the microprocessor or in a recording device 314. This process is 20 initiated by pressing the key AS in the key group T4. The screen then shows the text line "Recording" and 20 when the key "YES" in key group T3 is pressed, the A-image is recorded in the memory. When the key LZ is pressed, the instrument measures the transit time of the ultrasonic signals in a known manner by means of the metering circuit 327 which receives the ultrasonic signal from the line 347 and the clock frequency from line 351.

25 As shown in Figure 16, the writing unit 311 (Figure 11) comprises basically two modules. The first module 25 is responsible for the vertical (Y) deflection of the cathode ray and consists of an intermediate memory 330 connected to the data bus 340 of the microprocessor, a digital -analog converter 331 and an amplifier 332 whose output is connected to the line 350 and which, as shown in Figure 11, passes through the switch S and the amplifier 319 to the Y-deflection plate of the CRT.

30 The second module consists of a second intermediate memory 333, also connected to the data bus 340, a 30 shift register 334 and an electronic switch 335 whose output is connected to the line 354 in ig. 11; this line is connected to the control unit 310 which controls the Z-input of the CRT, i.e., the intensity of the beam. The transfer commands for the two intermediate memories 330 and 333 pass from the control bus 341 through a command decoder 336 to the inputs 360 and 316, respectively, of the two memories. The input 362 of the 35 shift register 334 is connected to the clock generator 323 shown in Figure 11 via the line 351. The decoder 336 35 can also pass a trigger pulse to the trigger generator 39 overthe line 365 to cause the latter to initiate the sawtooth signal. Finally, the decoder 336 is connected through lines 363 and 364 to the control lines 342 and 343, respectively, of the microprocessor.

The process of writing a line of text on the CRT is as follows: If, for example, the key MA for material data is 40 depressed, the microprocess 31 transmits the appropiate material data to the RAM 35 and the digital 40

information required to write the first line of text passes overthe data bus 340 to the intermediate memory 330; this information serves for controlling the Y-deflection of the beam. For this purpose, the intermediate memory 330 is activated by the control bus 341 via the control decoder 336 provided that a "Ready" signal from the I/O circuit 37 and delivered to the line 342 is present at the input 364 of the decoder 336. A strobe 45 signal is then returned through lines 363 and 343 to the I/O circuit 37. Subsequently, the data stored in the 45 intermediate memory 330 stand ready at the D/A converter 331 and the analog value produced there is amplified in the amplifier 332 to a voltage UY which passes overthe line 350 and the switch S and which,

after further amplification in the amplifier 319, is applied to the vertical (Y) deflection plates of the CRT,

causing the still dark electron beam to be aimed atthe upper left corner of the screen.

50 Subsequently, the first brightness control byte is taken from the selection RAM 35 and is loaded into the 50 intermediate memory 333 via the data bus 340 under the control of the control bus 341 and with the aid of the decoder 336. This digital value is transferred to the register 334 which operates as a parallel-series converter and which transfers the signals for a bright beam H and a dark beam L to the switch 335 in the rhythm of the clock frequency. This frequency on line 351 is started by the clock generator 323 only after the trigger 55 generator 39 has received the trigger pulse for starting the sawtooth voltage from the decoder 336 via the 55 line 351. Underthe influence of the sawtooth waveform, the electron beam travels from left to right along the upper image line while being modulated in intensity by the brightness control signals being taken out of the shift register 334 so as to cause illumination of the image points which constitute the line of text. While the shift register 334 is emptied, the next intensity control byte required forthe continuation of the text line is 60 prepared for uninterrupted transfer to the shift register 334. After the passage of sixteen intensity control 60

bytes, the electron beam has arrived atthe right edge of the screen, i.e., atthe end of the first image line of the first line of characters. During the fly-back of the beam, no intensity control bytes reach the line 354 and the screen remains dark. Subsequently, the intermediate memory 330, the converter 331 and the amplifier 332 reduce the vertical deflection voltage UY by an amount equal to one image line of a line of characters so 65 that the next sixteen intensity control bytes for forming the second image line of the first line of characters 65

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can be transmitted.

Each line of text or characters is composed of five image lines so that, after five complete writing processes, the first line of text is fully formed. At that time, the microprocessor shifts the beam downward by a distance equal to three image lines and starts the generation of the second line of characters. In a manner 5 similar to that of a TV scan, the lines of text are composed by sequential horizontal scans. The total amount of textual information may consist often lines of text with twenty-one characters per line, in the exemplary embodiment described here.

As already noted, each line or characters is composed of five lines of image points; after ten lines of text have been written, the electron beam is positioned in the lower right-hand corner of the screen.

10 The gate bar shown in Figure 15 is also generated by the circuit of Figure 16. The vertical position, i.e. the height, of the gate bar, which constitutes a threshold level, is formed by the intermediate memory 330, the converter 331 and the amplifier 332 and is applied to the vertical (Y) deflection plates of the CRT. The operator-selected values forthe start and width of the gate bar, entered by pressing the key MO and the appropriate keys in group T3 (Figure 12) are used by the microprocessor 31 to generate corresponding

15 traversing times for the electron beam so that the beam may be intensity-modulated in the manner required to place the gate bar at the correct position on the screen.

The ultrasonic test instrument described hereinabove is characterized by compact construction and convenient operation. It may be constructed as a portable unit capable of universal use. The internal computational and other features which are part of this invention relieve the operator of many of the

20 adjustments and calibrations which are necessary when using known instruments of this general type. A particularly advantageous feature of the present invention is that the cathode ray screen which is normally present forthe display ofthe echo signal information is used, additionally, forthe presentation of other information. The screen is used, in addition to the display ofthe echo signal, for presenting both selected and computed data, displaying legends and dimensions of these data, and displaying text and a monitor

25 signal gate bar related to the region of interest within the workpiece. All of these displays may be made atthe same time as the display ofthe echo signal. The data entry keys are grouped in convenient fields related to function in a way which makes possible a compact and practical construction.

Theforegoing description and illustrations relate to preferred exemplary embodiments and variants ofthe invention. These embodiments are to be regarded as serving the purpose of explanation and not limitation.

30 Various other embodiments, variants and contructions may be made and features of one embodiment used with another, all within the spirit and scope ofthe invention, the latter of which is defined by the appended claims.

Claims (17)

CLAIMS 35

1. An apparatus for displaying ultrasonic signals on the screen of a cathode ray tube, comprising:

a) a testing head (316) for radiating ultrasonic signals into a test object and for receiving echo signals reflected from inhomogeneities in the test object, including means for converting said echo signals into electrical signals which are applied to the vertical (Y) deflection plates ofthe cathode ray tube;

40 b) a trigger generator (39) for generating a sawtooth voltage applied to the horizontal (X) deflection plates ofthe CRT fortime-dependent deflection ofthe electron beam, said sawtooth voltage having a defined final amplitude and a traversing time which defines the imaging region within the test object;

c) a data entry keyboard (313) for setting the desired imaging region in the test object directly in units of length and for setting parameters related to the material ofthe test object and to the construction and type of

45 the testing head;

d) a microprocessor (31) including memory means for storing the parameters set on the keyboard and a computing circuit for computing the traversing time (tH) which defines the ulltrasonic imaging region within the test object and for computing the trigger delay time (tKv) which defines the delay between the emission ofthe ultrasonic signal and the onset of the traversing time and serving further for computing the time (tMB)

50 which defines the width ofthe detection window and the time (tMA) which defines the onset of the detection window subsequent to the emission ofthe ultrasonic signal; and e) a writing circuit (311) which is connected to the vertical (Y) deflection plates ofthe cathode ray tube via a switch (S)for producing a line raster signal and intensity modulation signals that cause a screen display of the parameters and values set in the data entry keyboard.

55

2. An apparatus according to claim 1, wherein said writing circuit (311) includes:

a) a first intermediate memory (330) for storing line height information derived from the microprocessor and a digital-analog converter for converting the contents ofthe memory to a Y-deflection voltage;

b) a second intermediate memory (333) for storing beam intensity information derived from the microprocessor and a shift register (334) the output of which is coupled to a switch element (335) for

60 controlling the beam intensity according to the contents ofthe memory.

3. An apparatus according to claim 2, further including a command decoder (336) for controlling the transfer of information into the first and second intermediate memories according to control data received from the microprocessor.

4. An apparatus according to claim 1, wherein the switch (S) is switchable between two states, one of

65 these states being devoted to the presentation of ultrasonic signals on the screen and the other of these

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states being devoted to the display of information placed in the apparatus via the keyboard.

5. An apparatus for displaying ultrasonic signals on the screen of a cathode ray tube, comprising:

a) a testing head for radiating an ultrasonic signal into a test object and for receiving echo signals reflected from inhomogeneities within the test object and means for converting said echo signals into

5 electrical signals applied to the vertical (Y) deflection plates of said cathode ray tube; 5

b) a trigger generator for producing a sawtooth voltage which is applied to the horizontal (X) deflection plates of the cathode ray tube for time-dependent deflection of the electron beam, said sawtooth voltage having a defined final amplitude and a traversing (rise/fall) time which defines the imaging region within the test object;

70 c) a data entry keyboard including a plurality of input keys ordered in functional groups forthe input and 10 binary coding of data related to the desired imaging region, the type and construction ofthe testing head, the properties of the test material and the representation ofthe detection window on the screen;

d) a microprocessor including memory means for storing the data entered via the keyboard and a computing unit for computing the traversing time, the trigger delay time, the onset time of the detection

15 window and the width and height of the detection window; and 15

e) a writing unit (311) for displaying the parameter values entered on the keyboard (313) and stored in memory.

6. An apparatus according to claim 5, wherein the keys on the keyboard (313) are arranged in groups as follows:

20 a) afirst group (Tt) including a keyfor each of the functions 20

presentation ofthe ultrasonic signal;

presentation of characters and text;

a mixture of signals and text;

b) a second group (T2) including a key for each of the functions

25 presenting data related to imaging region; 25

presenting data related to the testing head;

presenting data related to the material;

presenting data related to the detection window; and c) a third group (T3) for numerical data entry.

30 7. An apparatus according to claim 6, wherein the text representation provided by key group two (T2) 30 comprises a section for permanent text, a section for changeable data and a section for dimensions related to the changeable text.

8. An apparatus according to claim 7, including additional keys for positioning a cursor in a desired place on the screen to thereby select the data to be changed.

35 35

AMENDED CLAIMS

1. An ultrasonic test apparatus including a transducer for providing a signal representing an ultrasonic echo, a cathode ray tube for displaying said signal and a screen writing circuit for providing a signal

40 representing text matter to be displayed on the screen ofthe cathode ray tube, said writing circuit including: 40

a) a first intermediate memory for storing line height information derived from the microprocessor and a digital-analog converter for converting the contents ofthe memory to a vertical (Y) deflection voltage;

b) a second intermediate memory for storing beam intensity information derived from the microprocessor and a shift register the output of which is coupled to a first switch for controlling the beam intensity

45 according to the contents of the memory. 45

2. Apparatus according to Claim 1, further including a command decoder for controlling the transfer of information into the first and second intermediate memories according to control data received from a microprocessor.

3. Apparatus according to Claim 1 or Claim 2, including a second switch having a first condition in which

50 the signal representing an ultrasonic echo is supplied to the cathode ray tube and a seccond condition in 50

which the signal representing text matter is supplied to the tube, and means for setting said second switch in the condition appropriate to the display required.

4. Apparatus according to Claim 3, including a key operable to cause selected data to be read out and the second switch set in its second condition.

55 5. Apparatus according to any preceding claim, including a key operable to cause the second switch to 55 alternate between one condition and the other, the rate of such alternation being such that an observer perceives on the screen a composite display of ultrasonic information and text matter.

6. Apparatus according to any preceding claim, wherein said second switch is connected through an amplifier to the Y deflection plates of the cathode ray tube and the X deflection plates are corrected to the

60 output of a sweep generator for providing a saw-tooth voltage. 60

7. An apparatus for displaying ultrasonic signals on the screen of a cathode ray tube, comprising:

a) a testing head for radiating ultrasonic signals into a test object and for receiving echo signals reflected from inhomogeneities in the test object, including means for converting said echo signals into electrical signals which are applied to the vertical (Y) deflection plates ofthe cathode ray tube;

65 b) a trigger generator for generating a saw-tooth voltage applied to the horizontal (X) deflection plates of 65

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the CRT for time-dependent deflection of the electron beam, said saw-tooth voltage having a defined final amplitude and a traversing time which defines the imaging region within the test object;

c) a data entry keyboard for setting the desired imaging region in the test object directly in units of length and for setting parameters related to the material of the test object and to the construction and type ofthe

5 testing head;

d) A microprocessor including memory means for storing the parameters set on the keyboard and a computing circuit for computing the traversing time (tH) which defines the ultrasonic imaging region within the test object and for computing the trigger delay time (tKv) which defines the delay between the emission ofthe ultrasonic signal and the onset ofthe traversing time and serving further for computing the time (tMB)

10 which defines the width ofthe detection window and the time (tMA) which defines the onset of the detection window subsequent to the emission ofthe ultrasonic signal; and e) a writing circuit which is connected to the vertical (Y) deflection plates ofthe cathode ray tube via a switch for producing a line raster signal and intensity modulation signals that cause a screen display ofthe parameters and values set in the data entry keyboard;

15 f) said switch being switchable between two states, one of these states being devoted to the presentation of ultrasonic signals on the screen and the other of these states being devoted to the display of information placed in the apparatus via the keyboard.

8. An apparatus according to Claim 7, wherein said writing circuit includes:

a) a first intermediate memory for storing line height information derived from the microprocessor and a

20 digital-analog converter for converting the contents ofthe memory to a Y-deflection voltage;

b) a second intermediate memory for storing beam intensity information derived from the microprocessor and a shift register the output of which is coupled to a switch element for controlling the beam intensity according to the contents ofthe memory.

9. An apparatus according to Claim 8, further including a command decoder for controlling the transfer

25 of information into the first and second intermediate memories according to control data received from the microprocessor.

10. An apparatus for displaying ultrasonic signals on the screen of a cathode ray tube, comprising:

a) a testing head for radiating an ultrasonic signal into a test object and for receiving echo signals reflected from inhomogeneities within the test object and means for converting said echo signals into

30 electrical signals applied to the vertical (Y) deflection plates of said cathode ray tube;

b) a trigger generator for producing a saw-tooth voltage which is applied to the horizontal (X) deflection plates ofthe cathode ray tube for time-dependent deflection ofthe electron beam, said saw-tooth voltage having a defined final amplitude and a traversing (rise/fall) time which defines the imaging region within the test object;

35 c) a data entry keyboard including a plurality of input keys ordered in functional groups forthe input and binary coding of data related to the desired imaging region, the type and construction of the testing head, the properties ofthe test material and the representation ofthe detection window on the screen;

d) a microprocessor including memory means for storing the data entered via the keyboard and a computing unit for computing the traversing time, the trigger delay time, the onset time ofthe detection

40 window and the width and height ofthe detection window; and e) a writing unit for displaying the parameter values entered on the keyboard and stored in memory.

11. An apparatus according to Claim 10, wherein the keys on the keyboard are arranged in groups as follows:

a) a first group (T-|) including a key for each of the functions presentation ofthe ultrasonic signal;

45 presentation of characters and text;

a mixture of signals and text;

b) a second group (T2) including a key for each ofthe functions presenting data related to imaging region;

presenting data related to the testing head;

50 presenting data related to the material;

presenting data related to the detection window; and c) a third group (T3) for numerical data entry.

12. An apparatus according to Claim 11, wherein the text representation provided by key group two (T2) comprises a section for permanent text, a section for changeable data and a section for dimensions related

55 to the changeable text.

13. An apparatus according to Claim 12, including additional keys for positioning a cursor in a desired place on the screen to thereby select the data to be changed.

14. A method for operating an ultrasonic test apparatus wherein forthe representation of tables for a probe, material, cathode ray tube screen and monitor data as well as for the displaying of a headline in

60 addition to the measured A-scan, there is used a line by line formation with brightness modulation and the sweep frequency of a saw-tooth generator has a constant value different from the A-scan.

15. A method according to Claim 14, wherein digital information values, regarding the respective line height pass from a microprocessor to a first intermediate memory via a data bus ofthe apparatus, these information values are then converted into a corresponding analog value, subsequently amplified and finally

65 routed to the Y-plates of the cathode ray tube, digital brightness modulation values similarly reaching a

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second intermediate memory via the data bus, these values being then routed via a shift register and an electronic switch to the Z-input ofthe cathode ray tube, the transfer instruction for both the intermediate memories being given by a command decoder which is connected to the microprocessor via the control bus.

16. A method according to Claim 14 or Claim 15, wherein the microprocessor provides constant

5 brightness values for displaying a stored A-scan, whereby the corresponding digital information reaches the 5 Z-input ofthe cathode ray tube via the data bus, an intermediate memory and a shift register, the stored amplitude values ofthe A-scan being routed, via the data bus, a second intermediate memory, a digital analog converter and an amplifier to the Y-plates ofthe cathode ray tube.

17. A method for operating an ultrasonic test apparatus including a cathode ray tube for displaying test

10 results, wherein when displaying a monitor bar, the height of the bar is adjusted from a micro-processor via 10 a data bus, an intermediate memory, a digital/analog converter and a series-connected amplifier, which is connected to the Y-plates of the cathode ray tube, the start and the width of the monitor bar being determined by a real-time operating gate, whereby the gate signal activates the cathode ray tube by means of a switch.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1982. Published by The Patent Office, 25 Southampton Buifdings, London, WC2A 1AY, from which copies may be obtained.