DE3544095A1 - Device for calibrating analog real-time signals - Google Patents

Abstract

The invention relates to a device for the microprocessor-controlled detection, processing, displaying, storing and outputting of analog and/or digital measurement values from a number of measuring points or sensors, comprising a process computer in conjunction with a sequentially sampling measuring-point switch, an analog/digital and digital/analog converter, a number of analog amplifiers and analog and digital memories and a data input device and plug-in contacts for a plug-in-adaptor. The device allows the quasi-simultaneous processing of analog and digital measurement values and exhibits digital non-real-time-capable and analog real-time-capable output channels. The calibration with the sensors to be used is carried out semi-automatically in one version and fully automatically in another version.

Description

The invention relates to a device for microprocessor-controlled Acquisition, processing, display, storage and output of analog and / the digital measured values of several measuring points or sensors, with a process computer in connection with a sequential scanning Measuring point switch, an analog-digital and digital-analog converter, several analog amplifiers and analog and digital memories as well a data input device and plug contacts for a pluggable Adapter.

For the acquisition, processing, display, storage and output of analog and / or digital measured values, especially for a mobile Use, one strives to use portable devices and preferably here Pocket-sized devices, similar to a calculator.

For recording physical values such as pressures, temperatures or other measured values, corresponding sensors are available, which deliver both digital and analog signals. To improve the Determination of state variables or properties of a system, for example a hydraulic system, it is in many cases required or desirable, measured values of several at the same time Record sensors, process immediately and the results display or to supply a pen or printer.

Each sensor has its own characteristic, which when connecting on a measuring and evaluation device. This counts in particular its zero point position and that specified by the manufacturer Full scale or measuring range.

When using multiple sensors, there is therefore the problem that this Adapt measuring and evaluation device. They are already sensors known, which is equipped with its own compensation circuit are to make them sufficiently compatible, but they are Sensors are very complex and require their own energy supply.  

With the compensation circuit, for example, the temperature effect balanced, but not an existing zero point error, because this in operation, due to aging, short-term overload or the like changes.

In analog measuring devices, it is known for each sensor used Connection to the measuring device there to carry out an adjustment, whereby by Manual adjustment of a potentiometer, the zero point and the Final value, d. H. its measuring range can be set. The analog output signal Such a measuring device can be used to apply a recorder be used.

For processing digital input signals and application is the use of microprocessors to increase the power density of digital measuring devices necessary.

The present invention has for its object to provide measures and propose means to adapt a digital Measuring device to facilitate and to a variety of sensors automate. The invention is further based on the object To design digital measuring device such that at least one channel is present, from which real-time output signals are emitted.

To solve this problem is in the device listed above

a: each analog input via an analog amplifier with a constant Gain factor and a measuring point switch with an analog-digital Converter connected, which in turn via a process computer is linked to a digital memory which one measured once and amplified analog, digitally converted Zero point error of a sensor used can be called up;  

b: the digital memory from the data input device via the process computer controllable and stores one via the data input device entered calibration value of a sensor used available as its final value, and

c: the process computer via a digital-to-analog converter and one Analog amplifier for outputting a corrected signal with the Output connected.

With the output of an analog amplifier is temporary for storage Signals advantageously connected to an analog memory, its output has a tap in the measuring point switch.

In the detachable adapter part of the basic device is according to the invention Achieving a real-time output signal is also an electrical Actuatable switch available, the input of which on the one hand with the Output of a process computer controlled digital-to-analog converter and Analog amplifier and on the other hand with the output of an analog amplifier is connected and its output is a matchable Output amplifier is supplied.

The output amplifiers in the adapter part advantageously have electrically adjustable resistors.

The electrically controllable and adjustable resistors are for Carrying out an automatic comparison using the digital memory saved sensor-dependent zero point error and calibration end values Process controlled by the digital-to-analog converter.

The electrically controllable resistors are also field-effect transistors formed, which in one embodiment of the invention each via a digital-to-analog converter with the help of the processor are controllable.  

In a modified embodiment of the invention, the Field effect transistors from a common digital-to-analog converter can be controlled sequentially with the aid of a processor-controlled switch, the drive value achieved in a field effect transistor assigned analog memory is stored until this value by another is replaced.

The invention is described in more detail with reference to the drawings. Here demonstrate:

Figure 1 shows the basic circuit of a manually adjustable amplifier of a purely analog measuring device, according to the prior art.

Figure 2 shows the basic circuit of a semi-automatic tunable output amplifier with a processor, for one channel, according to the invention.

Fig. 3 shows the basic circuit of a fully automatically adjustable output amplifier with processor, for one channel, according to a further embodiment of the invention, and

Fig. 4 shows the schematic overall circuit of the basic device with adapter.

In Fig. 1, the basic circuit of a manually adjustable amplifier of a purely analog measuring device is shown schematically as prior art. The measurement input 1 is connected to the adjustable analog input amplifier 28 , the output of which leads to the display device. The output of the analog amplifier has a tap which is passed via an output amplifier 41 to a further evaluation device, such as a recorder (not shown). The potentiometers 29 and 30 are designed to be adjustable by hand, so that an adjustment must be carried out for each sensor used when connecting to the measuring device by adjusting the zero point and the final value, ie its measuring range, by adjusting a potentiometer by hand.

The analog output signal of such a measuring device can be applied a writer can be used directly, as already is executed at the beginning. Such a comparison is very time consuming.

Fig. 2 shows the basic circuit of a semi-automatic tunable output amplifier with processor for one channel of a digital measuring device. The analog measuring input 1 leads via an input amplifier 5 to an analog-digital converter 10 and further via a processor 11 to a digital-analog converter 14 . The present analog signal is fed to the analog output 23 via a switch 20 and output amplifier 21 . The resistors 29 and 30 can be adjusted manually, the resistor 29 being intended for the final adjustment or the calibration and the resistor 30 serving for the zero point adjustment. To achieve a real-time signal in a digital measuring device, the output 23 is connected via line 35 to the analog-digital converter 10 and the output of the input amplifier 5 via line 36 to the switch 20 . Based on the overall circuit of FIG. 4 will be discussed in more detail later this.

FIG. 3 shows the schematic circuit of an input and output channel of a digital measuring device with fully automatic calibration and a real-time signal output. Positions 10, 11 and 41 embody the basic device consisting of an analog-digital converter, a computer and a digital-analog converter.

The analog input 1 leads via an input amplifier 5 with constant gain. The amplifier is adjusted arithmetically. The switches 42, 48 and 49 are measuring point and control voltage changeover switches. The dashed line 19 indicates that the framed elements are housed in the adapter part.

This part is designed to be pluggable with the basic device. The output amplifier 50 is equipped with electrically controllable resistors 43 and 44 , which are designed as field-effect transistors. In front of each field-effect transistor 43 and 44 is an analog memory 46 and 47 , respectively, which stores the control voltage required to maintain the desired resistance, as provided by the digital-to-analog converter 41 and is varied until the desired resistance is achieved by successive approximation. The digital-to-analog converter then leaves this channel and the associated analog memory takes over the further maintenance of the voltage or the resulting resistance. The analog memory 46 with the field-effect transistor 43 is used to set the amplification factor of the amplifier 50 , while the analog memory 47 with the field-effect transistor 44 is used to set the zero point.

The input of the amplifier 50 can be switched over by the switch 49 , specifically once to the analog memory 45 and secondly directly to the analog signal to be output. In the normal operating phase, ie when the amplifier 50 has been adjusted, the switch 49 is switched to the analog input amplifier 5 and the faulty input signal runs via the input amplifier 5 . The end value is not related to the end of the measuring range and a zero point error is also still present. If the amplifier 50 is error-corrected as listed above, the desired configuration results, ie a corrected signal appears in real time at the output 23 .

For the necessary adjustment of the two resistors 43 and 44 , the switch 49 is disconnected from the analog input and is applied to the analog memory 45 . The computer feeds a calibration voltage into the analog memory via the digital-analog converter 41 and the switch 42 in the uppermost position, which voltage is held there. The computer measures the output voltage of the amplifier 50 via the digital-analog converter 41 and the switch 48 in the upper position.

If the input voltage is zero volts or one Voltage, which reflects the stored zero point error, can Zero point of the output amplifier can be adjusted.

The final value is calibrated in a similar way. The analog memories 45 , 46 and 47 ensure that the previously defined correction voltage for the zero point and the calibration voltage is maintained during the switchover of the switch 42 until these are replaced by new values. The field-effect transistors are therefore also supplied with the required voltage during the switching operations of the switch 42 , so that the necessary adjustment of the amplifier is ensured in every operating phase.

FIG. 4 shows the overall circuit of the digital measuring device with adapter 19 , the adapter here having the semi-automatic embodiment according to FIG. 2, which however can be replaced by the fully automatic version according to FIG. 3. In reference to FIGS. 2, 3 and 4, the same elements are provided with the same reference numerals.

The analog inputs 1, 2, 3 and 4 are connected through an analog amplifier 5, 6, 7 and 8 with a constant gain factor and a measuring point switch 9 with an analog-digital converter 10 , which in turn is linked to a digital memory 12 via a process computer 11 . The use of an input amplifier with a constant gain factor is possible according to the invention because the errors (offset voltage) inherent in the input amplifier are compensated for or corrected by means of the processor in connection with the zero point adjustment, which will be described in more detail below will.

The digital memory 12 stores a one-time measured and analog amplified and digitally converted zero point error of a sensor used. This value can be called up at any time.

The digital memory 12 is also fed data from the data input device 13 via the process computer 11 which corresponds to the predefined calibration values of a sensor used. These values are then saved as their final value and can be called up at any time.

The process computer 11 is connected to the output 16 via a digital-to-analog converter 14 and an analog amplifier 15 for outputting a corrected signal which is not real-time capable.

To store short-term signals, an analog memory 17 or 18 is connected to the output of an analog amplifier 5 or 6 , the output of which has a tap in the measuring point switch 9 .

In the adapter part 19 there is an electrically actuable switch 20 , the input of which is connected on the one hand to the output 16 of a process-controlled digital-to-analog converter with analog amplifier 15 and on the other hand to the output of an analog amplifier 5 or 6 , and the output of which is an adjustable output amplifier 21 or 22 is supplied. The output 23 or 24 of the output amplifier 21 or 22 is connected to the measuring point switch 9 .

The output amplifier 21 or 22 in the adapter 19 has electrically adjustable resistors 26 or 27 . The electrically controllable resistors 26 and 27 can be adjusted in a process-controlled manner by the analog-digital converter 10 in order to carry out a semi-automatic adjustment in this case with the aid of the sensor-dependent zero-point errors and end-of-calibration values stored in the digital memory 12 .

As already explained above, the part of this circuit can be replaced by the circuit according to FIG. 3, so that a fully automatic adjustment can be carried out.

The device according to the invention is further equipped with a digital measuring input 31, 32 and a digital output channel 34 which, for example, acts on a printer.

The connection 33 , which is connected to the energy source, not shown, serves to measure and monitor its own power supply. The computer can continuously measure the condition of its own battery via this measurement input.

With the device according to the invention described here, two pressure measuring points and two temperature measuring points can be processed quasi simultaneously. All channels can thus be occupied, the measured values of which are fed sequentially to the computer. The signals of the pressure transducer sensors, not shown in more detail, are switched directly and in parallel to two channels of the measuring point switch 9 , which is designed as a multiplexer, to two further channels, each of which is preceded by a fast analog memory 5 and 6 .

This method allows the detection of pressure peaks in a much shorter time than the circulation time of the multiplexer and the conversion time of the analog-digital converter 10 that occurs for each channel.

The natural zero point deviation of each sensor used is measured once by the device itself and the size of this deviation is stored in the digital memory 12 . The calibration value determined by the manufacturer of the pressure transducer sensors, ie the scaling of the measuring range end value of the sensors used in each case, is written into the digital memory 12 by the operator using the keyboard of the data input 13 . Instead of the keyboard, a bar code reader can also be used, each sensor having its calibration values in the form of a bar code. This avoids incorrect keying or confusion with a data sheet.

Every time a pressure measurement is made, it is stored in the memory stored data for the calculation of the absolute pressure from the current measured value used. Once stored in memory, remain this calibration data there until it is overwritten by the operator will. Thus, when changing the transducer system or systems, the usually complete readjustment of the analog input amplifier.

The acceptance of the actual zero point error as the new reference zero point, also allows the measurement of an absolute pressure above one certain existing form z. B. Measurement in a liquid filled system, in which the weight of the weight above the encoder The amount of liquid has already been preloaded with a static pressure.

When querying the analog memory instead of the direct pressure measurement channels through the computer, the last instead of the effective pressure values pressure peaks occurring at the respective pressure measuring channel processed will. The initially analog and digitally saved after the query Pressure peaks remain as measured values until they are reached by a occurring larger pressure peaks can be overwritten or from Operator deleted by keystroke and for a new one, by Zero outgoing peak measurement, be prepared.

Through the simultaneous processing of two separate measuring points and the use of a calculator is also a sum or difference Representation of the measured values possible.

The device according to the invention has two further input channels 3 and 4 , which are intended for temperature measurements. The fast analog memories, as are provided for pressure measurements by the memories 17 and 18 , are omitted here, since the temperature changes take place only relatively slowly in comparison to the pressure changes.

There is also a fully automatic calibration for the temperature sensors not necessary, as mainly standardized sensors are used, which do not require a new adjustment when changing. In principle, it is of course also possible here to use a fully automatic Perform an adjustment if this should be necessary.

With the device according to the invention it is also possible to digital Record and process measured values.

Such values result, for example, from the speed measurement. For this purpose, the digital measuring channels 31 and 32 for the direct processing of pulses from a digital sensor system, for. B. shaft revolutions per unit of time used.

Similar to the speed measurement, volume flows can also be measured and Perform flow measurements. Here, however, are those of the sensor system delivered counts per unit of time not directly processed.

The operator has the option of using the form factor in the keyboard Store digital memory. This factor contains data such as Device constant of a measuring turbine, influence of the viscosity of the Turbine driving medium and the like. From the actual The measured value and this factor stored in the memory is then calculated the actual measured variable is determined and for further processing provided.  

The following measurands are available for processing:
1. pressure at pressure measuring channel 1 ,
2. pressure at pressure measuring channel 2 ,
3. pressure peak value at pressure measuring channel 1 ,
4. pressure peak value at pressure measuring channel 2 ,
5. differential pressure of the two pressure measuring channels 1 and 2 ,
6. temperature at temperature measuring channel 3 ,
7. temperature at temperature measuring channel 4 ,
8. difference temperature of the two temperature measuring channels 3 and 4 ,
9. Speed on digital channel 31 and
10.Volume flow on digital channel 32 .

The following processing methods can be applied to the available measured quantities freely selectable by the operator.

1. Display
The device according to the invention has, for example, an LCD dot matrix display with two lines of 16 characters each. Up to two measured variables can be displayed simultaneously with their respective measuring units.

During the measurement, the operator can currently choose from the two Switch the displayed values to any other values.

2. Background storage
The pressure peaks that occur in the two pressure measurement channels are continuously stored in the memory, even if they are not called up for display. They can be called up at the push of a button.

3. Continuous storage in the memory
In a time cycle that can be selected by the operator, the measurement variables of a measurement channel, which can also be selected, can be stored in the memory in sequence. This process runs automatically, at most until the storage capacity is reached.

The data stored in this way can be saved at a later time - too after switching off the device in the meantime - via a serial Transfer the data interface to a printer or evaluation computer will.

4. Analog output (recorder output)
The recorded measured values of an analog channel can be output analog again in their present, uncorrected form. The output signal is proportional to the input signal, only its size is standardized with respect to the interface.

Claims (9)

1. Device for microprocessor-controlled detection, processing, display, storage and output of analog and / or digital measured values of several measuring points or sensors, with a process computer in connection with a sequentially scanning measuring point switch, an analog-digital and digital-analog converter, several Analog amplifiers and analog and digital memories as well as a data input device and plug contacts for an attachable adapter, characterized in that

• a: each analog input ( 1, 2, 3, 4 ) via an analog amplifier ( 5, 6, 7, 8 ) with a constant gain and a measuring point switch ( 9 ) with an analog-digital converter ( 10 ), which in turn is connected is linked via a process computer ( 11 ) to a digital memory ( 12 ) which stores a one-time measured and analog amplified, digitally converted zero point error of a sensor used;
• b: the digital memory ( 12 ) can be controlled by the data input device ( 13 ) via the process computer ( 11 ) and stores a calibration value of a sensor used as the end value, which can be called up via the data input device ( 13 ), and
• c: the process computer ( 11 ) is connected to the output ( 16 ) via a digital-to-analog converter ( 14 ) and an analog amplifier ( 15 ) for outputting a corrected signal.

2. Apparatus according to claim 1, characterized in that an analog memory ( 17, 18 ) is connected to the output of an analog amplifier ( 5, 6 ) for storing short-term signals, the output of which has a tap in the measuring point switch ( 9 ). 3. Apparatus according to claim 1 and 2, characterized in that an electrically actuable switch ( 20 ) is present in the adapter part ( 19 ), the input of which on the one hand to the output ( 16 ) of a process-controlled digital-to-analog converter with analog amplifier ( 15 ) and on the other hand, is connected to the output of an analog amplifier ( 5, 6 ) and the output of which is fed to an adjustable output amplifier ( 21, 22 ), and the output ( 23, 24 ) of the output amplifier ( 21, 22 ) is connected to the measuring point switch ( 9 ) . 4. Apparatus according to claim 1 and 2, characterized in that the output amplifier ( 21, 22 ) in the adapter ( 19 ) has electrically adjustable resistors ( 26, 27 ). 5. Apparatus according to claim 1, 2 or 3, characterized in that the electrically controllable resistors ( 26, 27 ) for carrying out an automatic adjustment with the aid of sensor-dependent zero-point errors and end-of-calibration values from analog-digital stored in digital memory ( 12 ) Transducers ( 10 ) can be adjusted in a process-controlled manner. 6. Apparatus according to claim 4 or 5, characterized in that the electrically controllable resistors are designed as field-effect transistors ( 43, 44 ), each of which can be controlled via a digital-to-analog converter with the aid of the processor ( 11 ). 7. The device according to claim 4 or 5, characterized in that the electrically controllable resistors are designed as field-effect transistors ( 43, 44 ) which of a common digital-to-analog converter ( 41 ) with the aid of a processor-controlled switch ( 42 ) can be controlled sequentially and the control value achieved is in each case stored in an analog memory ( 45, 46 and 44 ) assigned to the field effect transistor until this value is replaced by another. 8. The device according to claim 1 or one of the preceding claims, characterized in that at least one digital measuring input ( 31, 32 ) and a digital output channel ( 32 ) are present. 9. The device according to claim 1 or one of the preceding claims, characterized in that the data input ( 13 ) is designed as a keyboard and / or as a connection for a bar code reader.