DE1762987A1 - Device for studying particles suspended in a liquid - Google Patents

Description

Device for studying particles suspended in a liquid The invention relates to a method and an apparatus for counting Output pulses of a measuring device, e.g. B. a device for automatic counting of blood cells, a counter and a threshold value being provided, the defines a lower limit for the amplitude of the measurement pulses to be counted.

'in a method and a device according to this older proposal counting only measuring impulses that exceed this threshold value. Quickly successive Measurement pulses se can escape counting if the pulse intervals are smaller than corresponds to the recovery times of the circuits used.

The invention remedies this by providing that the bleßimpulse are fed to a selection amplifier connected downstream of the threshold value transmitter, which, in a manner known per se, generates a square pulse for the duration of the lower one The range of the measuring pulse exceeding the threshold value provides that this rectangular pulse is fed to a differentiator, which is known per se at the points in time of the pulse edges of the square pulse each generates a needle pulse, since that of the The needle pulse assigned to the leading edge is suppressed and that of the trailing edge associated bradelimpuls is used to control the counter.

The counting of the measuring pulses is therefore not based on the whole Pulse width, but after passing its trailing edge, so that not only the Dirt effects occurring on the leading edge remain unconsidered, but also the times necessary for the recovery of the circuits are certainly available stand. Counting by means of the trailing edge of the measuring pulse also enables to make the counting dependent on any conditions associated with the measuring pulse related, e.g. B. shape, size, pulse duration.

Another object of the invention is to provide only exile pulses to pay whose amplitude lies in a selected range. To solve this The invention provides a further object that the measuring pulses also one, one second threshold value transmitter downstream selection amplifier are supplied, the a square pulse for the duration of the range exceeding the upper threshold value of the meusimpulses supplies that this square pulse to a second differentiator is supplied, the one needle pulse assigned to the leading edge of the square pulse outputs that a blocking of a gate circuit, which is connected upstream of the counter, triggers at least for the duration of a measuring pulse.

These measures make it possible to measure those impulses from the count waste that exceeds the upper threshold.

In order to be able to adapt the device to given measuring conditions, according to the invention, at least one of the threshold value transmitters is used to set it Output voltage formed.

In order to be able to evaluate weak or distorted measuring impulses, see the invention, since # the meter is followed by a proportional amplifier, which emits the measurement signal to be evaluated to a device according to the invention. To the extensive elimination of protective effects and to ensure compliance with the specified The invention provides threshold values since # the selection amplifiers are threshold value limiters downstream are those for further evaluation from the selected university core emitted, almost rectangular impulses mask a suitable area.

The invention also solves the problem that immediately successively continuous particles which produce impulses that so quickly follow one another so that the gate circuit does not have time to return to the starting position remains before the second strong impulse arrives. Both impulses exceed the upper threshold, but only the first would be able to respond to the counting circuit to prevent.

According to the invention, the counting circuit is strong when a second arrives Signal automatically incapacitated for a sufficient time to avoid wrong counting. For this purpose, the invention provides that 3 an output of the control circuit is applied to a delay circuit in the timing circuit is that blocks the task of a counting pulse by this for a specified time.

The invention is explained in more detail below with reference to the drawing. In the drawing show: 1 shows a block diagram of a device, in which the invention finds application; Fig. 2 is a timing diagram as an example for lead pulses to be analyzed; Fig. 3 is a pulse plan from the measurement pulses in according to the invention derived pulses; 4 shows an overview of the conditions the emergence of the pulses according to FIG. 3; Fig. 5 shows the circuit diagram of the common Power supply device.

The invention is hereinafter in connection with its application explained in a device that the analysis of suspended in a liquid Particle serves, e.g. B. counting and sizing blood particles such as of blood cells.

Such a device. comprises a measuring apparatus, denoted by 20 in FIG and a number of Schaltgeinheit.

In the block diagram of FIG. 1, 20 denotes one of the possible usable measuring devices. This measuring apparatus is designated as 20 as a whole and essentially comprises two vessels 21 and 22 made of an electrically insulating one Material, with the inside forming a tube closed at the bottom and the outside consists of a simple cup, which is raised towards the closed tube (21) can be so that the lower end of the tube (21) into one in the outer vessel (22) contained liquid (24) is immersed.

In the wall near the bottom of the tube (21) there is a very small im following tactile opening called opening (26) is provided, the diameter of which is approximately between 20 and 200 microns. The tube 21 is filled with suspension 28, which of may be of the same or different nature as the liquid 24. In the liquid 24 particles are suspended, their number, (concentration) or other properties one wishes to examine. The upper end of the tube 21 is connected to a valve 30 connected to a vacuum source and connected to a lifting device 32.

The lifter 32 comprises a simple U-shaped mercury Elanometer arrangement, which an overflow capillary tube 34 open to the outside air, a horizontal one or has an almost horizontal measuring section 36 and a vertical section 38, which with the upper end of the tube 21 via a storage space 40 for mercury connected is.

If a vacuum acts on the liquid 28, the liquid 24 will penetrate the sensing opening 26 is sucked, the particles suspended in this liquid step through the tactile opening 26.

The tactile opening 26 is the only one between the interior of the two Vessels 21 and 22 have an electrical and physical connection. When to the A voltage is applied to the lead electrodes 48 and 50 introduced into the vessels a current from one electrode to the other can only run through the sensing opening 26. The tactile opening forms an electrical resistance, the size of which depends on the temperature, the ion concentration and other factors. The particles have a different conductivity than the liquid present in the tactile opening aU and consequently change the total resistance of the tactile opening when passing through it. These Change modulates the voltage drop iitu, r the tactile opening and generates a detectable one Signal.

Measurement pulses are picked up at the touch opening, as they are, for example are shown in FIG. Each measuring pulse corresponds to one through the tactile opening particles passing through, the momentum amplitude being somewhat greater than the size of the particle testifies.

All voltages in the device according to the invention come from a main energy source derived, which to an external line, preferably via a voltage converter is connected, the one or more substantially constant voltages gives away. One of the voltages delivered by the main source 94 (preferably in of the order of magnitude of about 6 volts), which keeps the mains frequency hum to a minimum halt, is supplied to the energy source (76) via the connection (93).

The block (75) in Fig. 1 is shown only for the sake of simplicity and as such, the apparatus 20 with insulating resistors, reversing switches and like. Represent. The connections 87 and 80 are only intended to show that they are suitable There are connections between the measuring apparatus and the circuit units.

The electrical measuring part of the device has a preamplifier 86 and a main amplifier 88 connected to it via connection 92. The preamplifier 86 is coupled to the tactile opening 26 and has an extremely small input resistance. The main amplifier 88 has a high input resistance, but is insofar unusual, as the stages are DC-coupled, but with the operating constants of an amplifier so that it acts like an AC amplifier behaves.

The main amplifier 88 has a high gain, for example of about 5000. The output of the Main amplifier is via one Connection 96 to a block 98 containing a high pass filter and rectifier placed. The filter is a small condensate or on the order of 25 picofarads, which is preceded by a diode.

The low-resistance output 100, which the signal from block 98 via containing connection 120 is an ac coupled cathode amplifier circuit. The output circuit 100 is used to control threshold value circuits and therefore stands over the connection 104, 105 and 106 in connection with selection amplifiers 110 and 108, respectively. The jiusgang circuit with low impedance prevents charging through the threshold circuits, d. H. the lower threshold circuit does not become the signal pulse load, causing an apparent change in the upper threshold level became. The phase inverter 112 is an anode amplifier circuit which the signal via connection 114-receives and the same via connection 118 to the baffles the cathode ray oscilloscope tubes 116 forwards. Other distraction circles are connected to the phase inversion stage.

The main amplifier 88 controls the alarm circuit via the connection 122 120. The alarm is audible or perceptible by means of a device 124 made and indicates that the tactile opening 26 either temporarily or permanently is clogged.

The main task of the output circuit 100 is the two selection amplifiers 108 and 110 to control. These amplifiers are excited and surrendered to satisfaction a linear gain only over a very small range, e.g. B.

6 volts, of the pulse received from the output circuit (100).

This 6 volt range is determined by the voltage at the cathodes Tubes in the selection amplifiers and the level of these voltages is selected controlled by the threshold value transmitter 82 and 84. The selected range of a pulse will reinforced and a section through the over connections 132 or 134 connected threshold value limiter 128, 130 is selected. Any selection booster has a gain of approximately five and controls the threshold limiters by a pulse part. The threshold limiters are made up of pairs of semiconductor diodes educated. Since any 6 volt range of the output pulse is used can, the bias is set on the threshold limiters. This can go through variable resistances or set by correctly selected milling resistors will.

The examination area can be chosen at will by appropriate choice its upper and lower threshold can be expanded.

In Fig. 1 are individual connecting lines between switching units those reference signs are added in brackets (as capital Latin letters), which correspond to the timing diagram of FIG. This means that these connecting lines lead the pulses shown in Fig. 3 and explained below.

The threshold limiters result in an approximate square pulse with an amplitude on the order of 2 volts compared to the 30 volts from the selection amplifier (6 volts times gain 5) and feed via the connections 140 or

142 the amplifiers 1) 6 and 138, which are used for light and dark control of the cathode ray tube 116 are used. These circles must receive the pulses without delay can pass on, because otherwise the connections via the connections 144 and 146 would be dem Cathode ray tube 116 supplied light and dark pulses not at the right time arrive. The gain of the light and dark control amplifier is of the order of magnitude from 15 to the cathode ray tube with a 30 volt pulse for light and dark control of the beam for the period selected between the two threshold values. The sharpness of the impulses and the short time span are achieved because the The bandwidth of this pulse amplifier is several megahertz.

The outputs of the light and dark control amplifiers 136 and 138 are also via connections 148 and 150 to further pulse amplifiers 70 and 152 connected. A network of diodes prevents the tubes of the pulse amplifiers from Draw grid current and ensure that there are small pulses near the baseline the light and dark control pulses are not lost. The impulse is on this Way in the pulse amplifiers further amplified about thirty times. The original one The pulse provided by the selection amplifiers is now considerably further amplified. If the original pulse from the main amplifier only by a very small amount is above the lower threshold, the part of the impulse which is above the threshold Gelant, amplified enough to switch the trigger circuit 66 via the connection 154.

These pulse amplifiers 70 and 152 with their double tube arrangements are provided twice so that it is possible to count or not to pay, depending on whether an impulse exceeds one or both threshold values. Exceeds it is the first threshold and not the second, it is counted. Exceeds If both threshold values are set, the number is suppressed. This is based on the following 3 explained. Bg. 3 represents a so-called pulse plan in which pulse shapes are plotted one below the other on horizontal time axes, but are vertical Stress axes different. The impulse schedule shows the at different points of the Device received signals (see. Fig. 1). blit A is the signal at the output of the Main amplifier, which occurs on line 104, designated. It is more positive than that MeB pulse 204 shown, the amplitude of which is from one to 100 volts and its duration (width) are in the order of 20 microseconds can. This impulse corresponds to a particle that passes through the tactile opening 26. The potentials labeled 156 and 158 are the lower resp. upper threshold values which determine the amplitude of the pulses to be examined. The critical times are at 160, namely when the pulse has reached the lower threshold and at 162 when it exceeds the upper threshold. The trailing edge of the pulse falls below the upper threshold value at 164 and the lower threshold value at 166. ne The one shown Pulse 204, which has an AmpEtude that is too high and therefore also the upper threshold value 158 should not be counted, for example. Only impulses which are below the threshold value 158 but above the threshold value 156, should be registered. To explain the invention, however, a pulse is discussed, which also exceeds the upper threshold value 158.

In the selection amplifiers 108, 110, the upper or lower part of the pulse 204 emitted by the main amplifier 88 under the control of the threshold value transmitter 82 and 84 cut off and only the area of the Momentum between the two thresholds, which is only of the order of a few Volts, boosted to about 10 volts (B and C in Figure 3). The amplitude of the two Signals (B and C) can be the same, but their width is different.

Of these pulses B and C, the one between the broken lines becomes in the illustration of FIG. 3 lying area, which is about 2 volts, however has different duration for the two pulses is selected. From this arise the square output pulses D and E on lines 140 and 142, respectively (Fig. 1).

These pulses are sent to the grid of tubes in the light and dark amplifiers 136 and 138 and boosted to about 30 volts so that the pulses F and G can be obtained. Connections 144 and 146 are used by these amplifiers the cathode ray of the oscilloscope tube 116 mr for the duration of the pulse while which it lies between the threshold values 156 and 158 is lightened.

A small fraction of the signal energy of the pulses F and G (as per the dashed lines indicated), is fed to the pulse amplifiers 70 and 152, respectively. These signals are shown at IS and I, respectively. Their amplitude is only a few volts and their duration is still different. This measure ensures that a Impulse which exceeds the given threshold by a small amount is amplified sufficiently is to switch the counting circuits even if it is not far enough over the Threshold is enough to control the cathode ray light and dark. The inventive The device is therefore extremely @ sensitive to the pulse amplitudes. That on the lower one Signal H triggered by threshold value 156 is converted into a square-wave pulse in pulse amplifier 70 amplified with an amplitude of about 190 volts, as shown at J, while the at the upper threshold value 158 triggered signal I into a square pulse with a Amplitude of about 250 volts is amplified, as shown at K. Both square pulses, which are referred to below as threshold value pulses are negative.

The leading edge 168 of the pulse associated with the upper threshold After it has been differentiated, K is sent to control circuit 1'70 via the connection 1 / given and thus delivers the trigger pulse 174 (trigger pulse) as a needle pulse, as shown at N. The control circuit 170 can also be referred to as an inverter flip-flop triggered by the trigger pulse 174 and the generation of a blocking signal, as shown at P.

The lock signal P is negative and is transmitted via connection 178 (as "negated input") of the gate circuit 176 supplied. The impulse caused by the trailing edge 180 of the threshold value pulse K would be triggered, is suppressed by diodes, such as this is usually done in a known manner in the event of undesired pulses.

Accordingly, the trailing edge 182 of the threshold value pulse J, der associated with the lower threshold 156, differentiated by a trigger pulse 184 (L) as a needle pulse, with the original through the leading edge 186 is suppressed. This trigger pulse thus obtained becomes 184 used to trigger the timing circuit 66.

The blocking signal P supplied to the gate circuit 176 switches it through Applying a negative bias to a tube so that it will last for the duration of the Presence of a blocking signal P emits no signal. It should be remembered that this blocking signal P resulted from the fact that the measurement signal exceeded the upper threshold 158 exceeded and that without exceeding the upper threshold, the blocking signal P would not exist, so that from other circuits of the device to the other input signals given to the gate circuit would be allowed to pass.

The trigger pulse 184 L in Fig. 3 is fed to the timing circuit 66, which delivers a square pulse M at its output. This is over the connection 186 is applied to the second input of the gate circuit 176. The time circuit 66 is as formed astable tilting circle, which triggered by the trigger pulse L, after some retires from its astable state in a few microseconds. If the gate circuit is permeable, i.e. if there is no pulse P, will the pulse is passed on to the counter 67 via the connection 188 as a counting signal. The trailing edge 190 of the pulse k becomes a reset pulse through differentiation 192, as shown at 0, which is sent to the control unit via connection 194 170 is supplied to this designed as a bistable multivibrator circuit reset to its original state.

A distinction can be made between three types of warning signals A: a) those who do not exceed the lower threshold 156; b) those who also exceed the upper threshold 158 and c) those who which are just between these two swell advertisements.

Those measurement signals which exceed the upper threshold will be suppressed because the blocking signal P prevents them from going through the gate to the payer 67 to arrive. Those small signals that do not exceed the lower threshold cannot generate a trigger pulse L and cannot trigger timing circuit 66. All other measurement signals are counted. The gate circuit 176 can be used as an AND gate a negated input (for the control pulse P) or as an EITHER-OR circuit be trained.

As can be seen from the block diagram, a connection 196 a delay pulse from the control circuit 170 to the timing circuit 66, to block this for a certain period of time. This is important when you are wants to receive essential statistical statements about counted impulses.

Assume a particle population in which a very small percentage dec of particles falls between two predetermined threshold values, while the rest significantly are larger particles that should not be counted. Is used by the device If the only unwanted particle is paid, then this constitutes a considerable one Errors, especially when the percentage of particles to be counted is a fraction one percent is. As a result, the time circuit 66 immediately after each strong If the signal is blocked, an immediately following pulse is prevented from counting regardless of whether it is large or small. The distribution of the smaller Particle is such, last the probability, a smaller particle because of Not counting this delay is much less than that, an undesirable one Counting particles.

FIG. 2 shows two such target pulses immediately following one another o04a and 204b. The critical times when the thresholds are exceeded are the same as shown in FIG. The times for the measuring pulse 204b are with provided with a line index. Exceeding the threshold 158 at time 162 controls the generation of the trigger pulse 174 N in Fig. 3 and the following Lock signal P.

Now comes a second measurement pulse 204b, which is also the upper threshold 158 exceeds the critical point in time for generating the blocking signal at 162 ', whereas the critical point in time for counting the first pulse (square pulse M) is 166 and the reset pulse C arrives some time later. Consequently the trigger pulse N generated by the second measuring pulse 204b occurs at a point in time in which the control circuit 170 still generates the locking signal P.

At the time 166 'when the measurement pulse 204b exceeds the lower threshold 156 falls below, the control circuit 170 can be switched again. Since abcr no trigger pulse 74 As soon as N arises, a signal lui would go through the gate circuit 176 and the meter pulse 204b can be counted.

The pulse M assigned to the first measuring pulse 204a would be via the Reset pulse 0 cause the blocking pulse P to be terminated. The second Threshold value pulse K assigned to measurement pulse 204b was indeed over its leading edge bring the trigger pulse N, which however does not generate a new control pulse P. able because the first blocking pulse P still lasts. On the other hand, the second would Pulse M associated with measuring pulse 204b subsequently cause an unwanted counting.

The arrangement which prevents this is a tube circuit, which the time circuit 66 after the occurrence of a strong measuring pulse a04 for a period of time blocks, which is longer than the normal duration of the pulse J and thereby the Counting of immediately following impulses prevented. For example, locking the Time circle 66 up to the point in time 19 ig. L) expand so that the measuring pulse 204B cannot generate a count signal to 1ö8 if it exceeds the threshold 1% falls below at 106 '.

Lies a helmsman. pulse P, then the time circuit is set via line 196 b6 blocked. This blocking must be effective for a longer period of time than the duration of a threshold pulse is normally J. First the back flank of a new threshold value pulse J, that of a subsequent, not shown Read signal was triggered, can then control the timing circuit 66, so there then a pulse M is able to arise which cancels the blocking pulse P, which is still ongoing.

Statistical corrections established through tests and calculations and from the distribution and simultaneous passage of particles through the tactile aperture are usually applied to the results and reduce the consequences of not counting small pulses with a large accumulation to a minimum.

4 shows a summary of the sequence of the individual processes.

Fig. 5 shows the circuit diagram of the common power supply for di entire device. The power supply of the reading section 27 wrd through reaches a transformer (T-1), on its secondary winding (S3 and S-4) after Rectification DC power is removed. The common TransSormator primary winding is labeled P-1. The secondary winding Th-1 and Th-2 for threshold value sensors are closely coupled to the secondary windings S-3 and S-4. These thresholds serve to count or register Me # pulses with specific amplitudes to be able to choose. The primary winding P-1 is preferably on the same part of the transformer core so that # the coupling between all these windings is very tight. It is essential that the current over the measurement path 27 is kept largely constant at all times. This only refers to here the current over the measuring section, since the supply current is not modulated. It was already pointed out that changes in resistance across the tactile opening 26 do not influence the signal output as long as the measuring path current is constant is held.

This can be achieved by automatically regulating the power supply to compensate for any changes in the current applied to the measuring path seeks.

The transformer T-1 has a winding in addition to those mentioned S-5. This is a heating voltage winding with resistors R-37, R-38, R-39 and R-40 neutralized center. The winding S-6 is a high voltage winding, which with the help of the rectifier D-1 and filters R-36, C-21 the positive voltage for the measuring section 27 and across the resistors R-41 and R-42 the positive voltage for the grid 252 of the tube V-10 and the anode 254 of the pentode V-9 with the in the circuit diagram delivers specified values.

The winding S-3 provides with the help of the diode D-2 and the filter R-43, C-22 a positive voltage for the screen grid 256 of the pentode V-9, where the Windings S-6 and S-3 have a common ground.

The winding S-4 generates by means of the diode D-3 and the filter R-45, C-23, C-26, R-44, a negative voltage for the control grid 258 of the pentode V-9. The positive voltage is applied to cathodes 260 through variable resistor R-46 Tube V-10 laid. The tap of the resistor R-46 is on a common Connection line on the other windings S-3 and S-6 and on the cathode 262 of tube V-9 with control grid 258 negatively biased by several volts.

The resistor R-46 limits the in the tube V-10 and thus the over the measuring section 27 flowing current. The anodes 251 of the tube V-10 are over the Line 223 and the pole changer S-1 with the measuring section 27 and with the input of the Measuring amplifier 86 connected. The DC circuit over the test section is by means of of the resistors R-8 and R-9 via the pole changer S-1 and the conductor 222 to the winding S-6 closed.

The circuit of winding S-3 expediently serves as an independent one Price circle for the screen grid 256 of the tube V-9.

The circuit of winding S-4 provides the reference voltage between the cathodes 260 of tube V-10 and the control grid 258 of tube V-9 with which the voltage across resistor R-46 is compared. The tensions build up as explained below, so that large voltages are present on R-46 can and the voltage between grid 258 and cathode 262 of tube V-9 only experiences very small changes. The anode 254 of tube V-9 is with the grid 252 of the tube V-10. If there is a change during operation of the device of the total current flowing through the tube V-10, which is the measuring path current this change will manifest itself as a change in the voltage drop across show the resistor R-46. This will influence the current flow in the tube V-9, because this voltage is continuously compared with the reference voltage. The bias of the grid 258 opposite the cathode 262 is affected. Makes this change noticeable by a change in the current flow through the anode circuit of the tube V-9 ; and since this anode circuit is connected to grid 252, any change will of current flow through V-10 by increasing or decreasing the voltage between Counteracted grid and cathode. This circuit is extremely sensitive, since the grid voltage of the tube V-10 only needs to fluctuate very little in order to achieve great To cause changes in the anode current. The tube V-9 works hard with it stabilizing with the result that with a large range of changes of Measuring section resistance a constant measuring section current is maintained.

Claims (18)

P a t e n t a n s p r ü c h e 1. Procedure for counting output pulses a measuring device, e.g. B. a device for the automatic counting of blood cells, with a counter and with a threshold value transmitter that sets a lower limit for the Determines the amplitude of the measuring pulses to be counted, characterized in that the measuring pulses (204) is supplied to a selection amplifier (108) connected downstream of the threshold value transmitter (8) are, in a known manner, a square pulse (8) for the duration of supplies the range of the Keßimpuls which exceeds the lower threshold value (156), that this square pulse is fed to a differentiator, which in itself as is known, one each at the times of the pulse edges of the square pulse Needle pulse generates that the needle pulse assigned to the leading edge suppresses is, and that the trailing edge associated needle pulse (184) for controlling the Counter (67) is used. 2. The method according to claim 1, characterized in that the measuring pulses (204) also to a selection amplifier connected downstream of a second threshold value generator (84) (110) are fed to the one square pulse (C) for the duration of the upper one Threshold value (158) exceeding Range of the measuring pulse supplies that this square pulse is fed to a second differentiating element, that emits a needle pulse (174) assigned to the leading edge of the square pulse, the one blocking of a gate circuit (176), which is connected upstream of the counter (67), triggers at least for the duration of a measuring pulse. 3. Device for counting output pulses of a measuring device, e.g. B. a device for automatic counting of blood cells, with a counter and with a threshold value transmitter that sets a lower limit for the amplitude to be counted Determines measuring pulses for carrying out the method according to Claim 1 or 2, characterized by a selection amplifier (108) connected downstream of the threshold value transmitter (82), to which the measurement pulses (204) are fed (104) that during the exceeding of the threshold value, a square pulse (182) is formed from its trailing edge a needle pulse (184) is derived by differentiation, which is considered astable Tilt circuit formed timing circuit (66) controls, which in turn with the counter (67) is connected, and that the differentiation results from the leading edge the needle pulse resulting from the square pulse is suppressed. 4. Apparatus according to claim 3, characterized in that a second one Threshold value transmitter (84) is provided, which has an upper limit (158) for the amplitude to be counted measuring pulses (204) specifies that this threshold value transmitter a second The selection amplifier (110) is connected downstream to which the measurement pulses are fed (106), that when the second threshold value is exceeded, a further square pulse (180) is formed, from the leading edge of which a needle pulse (174) is differentiated is derived, which triggers a locking signal in a control circuit (170) and its needle pulse arising from the trailing edge is suppressed and that the control circuit (170) which is followed by an input of a gate circuit (176), the second of which Input (186) is connected to the timing circuit (66), being over the blocking signal blocking the gate circuit is fed to the second input and the output (188) of the gate circuit is connected to the counter (67). 5. Apparatus according to claim 3 and 4, characterized in that the measuring device (20) is followed by a proportional amplifier 86, 88) which supplies the measuring signal is. 6. Apparatus according to claim 3 or 4, characterized in that dad the selection amplifiers (108 or 110), threshold value limiters (128 or 130) are connected downstream are. 7. Device according to one of claims 3 to 6, characterized in that that at least one of the threshold value transmitter (82, 84) for setting the output voltage is trained. 8. Device according to one of claims 3 to 7, characterized in that that the selection amplifier or the selection amplifiers (108 and 110) pulse amplifier (70 or 152) are connected downstream, the threshold value pulses (J or K) for the timing circuit (66) or the control circuit (170). 9. Apparatus according to claim 4, characterized in that the control circuit (170) has a bistable flip-flop, which from the leading edge through Differentiation formed needle pulses (174) as a trigger pulse in the one stable State and from a pulse (192) of the timing circuit (66) as a reset pulse in the other stable state is reset and in the first-mentioned switching state emits a blocking signal (P) to the gate circuit (176). 10. Device according to one of claims 3 to 9, characterized in that that the time circle (66) has an astable flip-flop that is generated by the needle pulse (184) of its differentiating element is triggered as a trigger pulse and a pulse (M) delivers to another differentiator that Facilities to suppress the leading edge pulse and the trailing edge pulse (192) as a reset pulse to the control circuit (170) via its output (194). 11. The device according to claim 10, characterized in that a further output (196) of the control circuit (170) to a delay circuit in the time circuit (66) is placed, which is the astable trigger stage of the time circuit for a locks the specified time. 12. Device according to one of claims 4 to 11, characterized in that that the gate circuit (176) is designed as an AND circuit. 13. Device according to one of claims 9 to 12, characterized in that that the from the astable multivibrator of the time circuit (66) emitted pulse (M) as Counting pulse is sent to the gate circuit (176) and from there to the counter (67) is placed (188). 14. Device according to one of the preceding claims, characterized in that that threshold voltage from a common, also serving as a measuring current source Power supply device (76) is derived. 15. The device according to claim 14, characterized in that the common power supply device (76) both the first threshold voltage and the second threshold voltage are derived. 16. Device according to one of claims 14 or 15, characterized in that that the first and the second threshold voltage are adjustable and only pulses let through between the two threshold voltages. 17. Device according to one of claims 14 to 16, characterized in that that a transformer with a primary winding (R1) and three closely coupled secondary windings is provided, one of which is provided with rectifiers secondary winding (S-4, S-3, S-5, S-6) serves as the MeB current source, while the other two secondary windings (TH-1, TH-2) are used to generate the threshold voltages. 18. Device according to one of the preceding claims, characterized in that that a cathode ray tube (116) is provided, which via devices (112, 136, 138) the measuring pulses are supplied in such a way that only pulses within a presettable Range of pulse amplitudes the cathode ray tube lights up.