SU1307404A1 - Device for contactless measurement of pulsed current - Google Patents

Abstract

The invention can be used for contactless control of electrical signals in nodes and blocks of electronic equipment. The purpose of the invention is to improve the measurement accuracy. The device contains a generator of I stimulating pulses connected to the diagnosed bus 2 of the printed circuit board 3, a contactless electromagnetic current sensor 4, an amplifier 5, a threshold unit 9 and a display unit 12. A phase inverter 6, an adder 7, a delay line 8, registers 10 and 13 of amplitude and sign, a code-converter 11, an IL 14 element and a synchronization unit 15 are entered into the device. Due to this, in the presence of a pulse noise in the amplitude register 10, only the amplitude value of the useful pulse is recorded, taking into account the sign. In this case, the influence of interference on the measurement result is excluded. 1 hp ff, 2 ill. € cl about 4; about 4;

Description

one

The invention relates to a measurement technique and can be used for the non-contact monitoring of electrical signals in nodes and blocks of electronic equipment in the diagnosis of failures and localization of faulty elements mounted on printed circuit boards.

The purpose of the invention is to improve the measurement accuracy.

Figure 1 presents the scheme of the proposed device, nafig. 2-time diagram of the device.

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The device contains a generator of 1 stimulating pulses connected to the diagnosed bus 2 of the printed circuit board 3 of the monitored digital unit. The contactless electromagnetic current sensor 4 is connected via amplifier 5 to a phase inverter 6, whose direct output is connected to the first input of the adder 7, and the inverse output through the first delay line 8 to the second input of the adder 7 The output of the adder 7 is connected to the first input of the threshold unit 9, the outputs which through the register 10 amplitude and the Converter 11 code is connected to the first inputs of the display unit 12 and the register 13 characters, the outputs of which are through the logical element OR 14 and connected to the second input of the display unit 12. The generator 1 is connected to the input of the synchronization unit 15, the first output of which is connected to the inputs of the installation in the initial state of the amplitude register 10 and the register of 13 characters. The second and third outputs of the synchronization unit are connected respectively to the gate input of the threshold unit 9 and information inputs of the register 13 characters. The first 16 and second 17 outputs of the device are connected

respectively with the first and second pulse shifted relative to one

generator 1 moves. Synchronization unit 15 contains pending multivibrators 18 and 19, delay line 20 and standby multivibrator 21. The inputs of multivibrators 18 and 19 are connected to the input of block 15 and, via a delay line 20, to the input of multivibrator 21. The first, second and third outputs of block 15 are connected respectively to the outputs of multivibrators 18 and 19 and 21.

The device works as follows.

The generator 1 stimulating pulses generates pulses (figure 2, a, b.

the other for the time with, determined by the delay line 8, the polarity of the first pulse U of the signal coincides with the polarity of the increment of the measured current. The signal U, from the output of the adder 7, is fed to the input of the threshold unit 9, performed on comparators with gating, and the comparators whose comparing level is higher than DiaeT, triggers. These comparators are switched on exit to state 1, and O are left at the output of the other comparators. Thus, in the threshold block

ten

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c) which are fed to the input of the synchronization unit 15 and through the outputs 16 and 17 are applied to the tested bus 2 of the diagnosed PCB 3, creating current pulses i in it, the magnitude and direction of which characterize the type and location of the malfunction. In particular, if the bus at any point is shorted to ground, then 1 1 current pulse i has a positive polarity (FIG. 2a) i.e. corresponds to the current flowing out (from the generator), and vice versa, if the bus is shorted to the power source, the impulse current i changes direction (Fig.26), i.e. flows into the generator. By measuring the magnitude and direction of the current in individual branches x of the common bus, the location of the fault is localized and the branch in which the current is greatest is faulty. For measurements, a contactless electromagnetic current sensor 4 is mounted on the conductor to be tested with current 1, which creates a proportional pulsed magnetic field around it. At the moments of formation of the current pulse fronts in the winding of the electromagnetic sensor 4, short voltage pulses are indicated (Fig. 2 a, b, c), the amplitude of which is proportional to the amplitude of the current pulses 1, and the polarity depends on the current direction.

20

25

thirty

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I

The pulses after amplification by amplifier 5 are fed to the input of phase inverter 6. The signal from the inverted output of phase inverter 6 is delayed by the delay line 8 for time 2 (U-} Fig. 2) and summed with the signal from the direct output of phase inverter 6. Thus , the signal Od output of the adder 7 is two

the other for the time with, determined by the delay line 8, the polarity of the first pulse U of the signal coincides with the polarity of the increment of the measured current. The signal U, from the output of the adder 7, is fed to the input of the threshold unit 9, performed on comparators with gating, and triggers the operation of those comparators whose comparison level is higher than DiaeT. These comparators are switched on exit to state 1, and O are left at the output of the remaining comparators. Thus, in the threshold block

the positive pulses of the signal ij are transformed into a single normal code, which is fed from the outputs of the threshold block to the information inputs (5-inputs) of the amplitude register 10 and is recorded in it.

The code converter 11 continuously converts a single normal code at the output of the amplitude register 10 into a natural binary-decimal code that controls the display unit 12 and simultaneously supplies the synchronization inputs with the C-inputs of the character register 13.

With the arrival of the leading edge of the pulse U from the generator 1, Fig. 2 a), the simultaneously waiting multivibrators 18 and 9 of the synchronization unit 15 are started simultaneously. The pending multivibrator 21 is started with a delay relative to the pulse edge U, for the time determined by the delay line 20, the delay time of which must be equal to the delay time of the first delay line 8. The multivibrator 19 forms a short reset pulse Ug (Fig. 2), which is applied to the R inputs of the registers 10; 13 and brings them to the initial state. The multivibrator 18 generates a pulse of the first strobe U (Fig. 2, during which the maximum value of the output code of the threshold block 9 is recorded in the amplitude register 10). This happens as follows.

The strobe impulse U g arrives at the input of the gating of the threshold unit 9 and thereby allows its operation during its operation time. From the output of the threshold block 9, the unit normal code enters the 5 inputs of the register 10. The register 10, built on the R5 triggers, stores the maximum code value at the output of the threshold block 9 and stores this code until the next reset pulse Us — the Multivibrator 21 generates the pulse of the second gate 1) (Fig. 2) is half the duration of the pulse of the first gate U which arrives with a delay of cG relative to the front of the first gate U to the information inputs (O-inputs) of the register 13 of the sign and thereby resolves act Record a signal of high level in the register 13. Pulse duration per074044

strobe I is selected so that during its operation from adder 7 both yg pulses are forgiven and (positive and negative), 5 occurring when the sensor 4 converts the leading edge of the measured current pulse i, and for the duration of the second gate pulse {J-, twice as long as O, the first gate passes only the second voltage pulse U, shifting from the first by time (Fig. 2a).

15 A positive pulse of the signal tJ, j causes the operation of those comparators of threshold block 9, the level of comparison of which it exceeds in amplitude, therefore recorded in the register

2Q 10 output states of the threshold block comparators characterize the amplitude value of the signal i. Recorded in register 10 values through the code converter 11 are received

5 to the display unit 12 and to the synchronization inputs of the register of 13 characters, on the information inputs of which the pulse of the second gate U- arrives. This pulse is written to register 13 and

0 is transmitted through the element OR 14 to the sign bit of block 12 as a minus sign only if, during the time of the strobe pulse Y, a code change takes place on the course of the code converter 11. Consequently, when the measured current is positive (Fig. 2a), when the first pulse EJ is positive in the U4 signal and the second E. negative, the value of the first pulse E, .a second negative pulse coinciding in the amplitude register 10 is recorded. in time with the pulse of the second strobe 11, does not cause a change in the code at the output of the converter 11 in the code. The outputs of the converter 11 are connected to the synchronization inputs of the register 13 characters, and the information inputs of the register 13 are fed with the pulse of the second gate (J, which is

in the absence of a synchronization signal, it is not recorded in the register 13, and the bit of the display unit 12 corresponds to the plus sign. When the current direction i is negative (fig.2b) in the signal U, the first pulse becomes negative and the second pulse positive, therefore the recording of a positive pulse in amplitude register 10 coincides with the pulse of the second gate U- ,. Consequently, at least one of the synchronous inputs of the register of the sign 13, a signal level drop occurs during the time of the gate and at least one of the bits of the register of the mark sign 13 records a high logic level, and a voltage drop U g occurs on the sign bit of the display unit 12, corresponding to signal minus. Thus, the proposed device provides a contactless measurement and indication of the current amplitude, taking into account the sign.

The device operates in the same way and in the presence of impulse noise caused by parasitic surge at the switching front of the measured current of Fig. 2c. In this case, the signal 0, which enters the input of the threshold unit 9, contains two pulses of positive polarity with amplitudes E and E, the first of which (EJ is due to pulsed interference, and the second (E4) is due to the useful switch signal of the tested circuit to logical state. When a signal is input to the threshold unit 9, the amplitude amplitude EI is first converted and recorded into register 10, then the amplitude E of the second signal is written to register 10 in the same way. If there is more interference amplitude E, then the pulse E of the useful signal coinciding in time with the Btoporo pulse of the U-J5 strobe triggers the higher bits of the threshold block and increases the code in the register 10. The code change during the strobe time and 7 results, as shown previously, to an entry in register 13 and block 2 minus signs.

one

 the third waiting multivibrators and the delay line, the inputs of the first and second multivibrators waiting are connected to the input of the synchronization unit and through the delay line to the third input

Thus, in the presence of impulse noise in register 10, only the value of the amplitude of the useful pulse is recorded, taking into account the sign, and the effect is 50 of the standby multivibrator, and the first, interference effect on the measurement result is the second and third outputs of the sync block, which allows to increase they are connected respectively with the accuracy of contactless measurement of the outputs of the first, second and third pulsed current of its multivibrators.

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1. A device for contactless measurement of pulsed current, containing a stimulating pulse generator, the first and second outputs of which are connected to the first and second outputs of the device, a contactless electromagnetic current sensor connected to an amplifier input, a threshold unit and a display unit, characterized in that accuracy of measurement; a phase inverter, an adder, delay lines, storing amplitude and sign registers, a code converter, an OR element and a synchronization unit, and an output the silicon is connected to the phase inverter input, the direct output of which is connected to the first input of the adder, and the inverse step is connected via a delay line to the second input of the adder, the output of which is connected to the input of the threshold unit, the output of which is connected to the amplitude register input, the output of which is through the code converter connected to the first inputs of the display unit and the information input of the register of the mark, the output of which through the logical element OR is connected to the second input of the display unit, the third output of the generator I pulses coupled to Stimulates

5; the input of the synchronization unit, the first output of which is connected to the setup input to the initial state of the amplitude register and the sign register, the second output to the gate input of the threshold unit, the third output to the gate input of the sign register.

2. The device according to A.1, about T and - the fact that the synchronization unit contains the first, second and

 the third waiting multivibrators and the delay line, the inputs of the first and second multivibrators waiting are connected to the input of the synchronization unit and through the delay line to the third input

0

0

0 standby multivibrator, and the first, second, and third outputs of the synchronization unit are connected respectively to the outputs of the first, second, and third multivibrators.

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Claims (2)

Claim (. A device for contactless measurement of pulsed current, containing a stimulating pulse generator, the first and second outputs of which are connected to the first and second outputs of the device, a contactless electromagnetic current sensor connected 10 to the amplifier input, a threshold unit and an indication unit, characterized in that, in order to improve the accuracy of measurement, a phase inverter, a total of 15 torr, a delay line, memory registers of the amplitude and sign, a code converter, an OR element, and a synchronization block are additionally introduced, while the output the amplifier is connected to the input of the phase inverter, 20 whose direct output is connected directly to the first input of the adder, and the inverse output is connected via a delay line to the second input of the adder, the output of which is connected to the 25 input of the threshold block, the output of which is connected to the input of the amplitude register, the output of which is through the converter the code is connected to the first inputs of the display unit and the information input of the sign register, the output of which through a logic element OR is connected to the second input of the display unit, the third output of the generator with stimulating pulses is connected to the 35th input of the synchronization block, the first output of which is connected to the installation input in the initial state of the amplitude register and sign register, the second output is with the gate input of the threshold block 40, and the third output is with the gate of the sign register. 2. The device according to claim 1, wherein the synchronization unit comprises a first, second and 45 third standby multivibrators and a delay line, the inputs of the first and second standby multivibrators are connected to the input of the synchronization block and through the delay line to the input of the third 50 multivibrator, and the first, second and third outputs of the synchronization unit are connected respectively to the outputs of the first, second and third waiting multivibrators. Figure 2.