CN202339390U - Bad contact detection device for instrument test line - Google Patents

Abstract

The utility model relates to a bad contact detection device for an instrument test line. The bad contact detection device comprises a sampling control signal generator, a first-level undersampling circuit, a second-level undersampling circuit and a band-pass filter, wherein the first output end of the sampling control signal generator is connected with the control signal input end of the first-level undersampling circuit; the second output end of the sampling control signal generator is connected with the control signal input end of the second-level undersampling circuit; the signal output end of the first-level undersampling circuit is conncted with the signal input end of the second-level undersampling circuit; and the signal output end of the second-level undersampling circuit is connected with the band-pass filter. The bad contact detection device for an instrument test line has the advantages of low cost, can convert a high-frequency signal into a low-frequency signal and is especially suitable for a component detection device.

Description

Meter Test line loose contact pick-up unit

Technical field

The utility model relates to instrument detection technique field, particularly a kind of Meter Test line loose contact pick-up unit when being used for LCR electric bridge, low resistance test, internal resistance of cell test etc. and detecting.

Background technology

For the components and parts of resistance or electric bridge class, producing whether qualified detection that all needs man-hour it.Usually can adopt instrument that it is detected, be provided with four p-wire transmission lines on this instrument, respectively with the HC of Meter Test end; HP, LC, LP connects; The other end at each bar p-wire; The other end of two p-wires is connected on the same clamping device, like this, has connected a voltage sample p-wire and a current drives p-wire on each clamping device.During use, two clamping devices are clamped in the two ends of element to be detected respectively, can carry out whether qualified detection.

Along with the progress of science and technology, the measurement accuracy of detecting instrument is had higher requirement, because the apparatus measures result's that the loose contact of p-wire itself or broken string cause error causes qualification rate to reduce.So also just increased the client and detected the measured piece probability of errors, probably defective products has been used as the non-defective unit use, perhaps non-defective unit has been judged to defective products and has abandoned.

Therefore, at present, numerous clients hopes to have a kind of like this means, and whether contact that can automatic tester table p-wire is reliable, thereby can significantly reduce the erroneous judgement situation of test measured piece.In existing technology owing to there are not such means, be merely able to usually by client oneself find test not to after, manual work is injected p-wire again measurement port and is checked whether test data correct, and such judgement itself also possibly have problems.Based on such demand and perfect to the continuous pursuit of properties of product, we have designed such testing circuit that is used for the p-wire loose contact,

Summary of the invention

The purpose of the utility model is to provide a kind of Meter Test line loose contact pick-up unit; When adopting the Meter Test measured piece; If a certain loose contact in four p-wires or broken string; Can detect through this pick-up unit so, and logical display screen shows the result of p-wire loose contact or broken string.

The technical scheme that realizes the utility model is following:

Meter Test line loose contact pick-up unit is characterized in that, comprising:

The signal amplification module, this signal amplification module carries out the amplification of signal amplitude with p-wire voltage sample end signal; And

Reference signal source module, this reference signal source module provide a ripple that exchanges with the voltage sampling signal different frequency; And

The voltage sampling signal synthesis module synthesizes the signal of the signal amplification module that receives and the signal of reference signal source, obtains voltage sample end composite signal; And

The voltage sample comparison module compares the signal of the voltage sampling signal synthesis module output positive and negative voltage with a setting, thereby obtains the whether comparison signal of loose contact of voltage sample end; And

Current drive signal module for the sampled signal of p-wire current drives end; And

The current sample comparison module compares the current sampling signal of the current drive signal module output positive and negative level with a setting, thereby obtains the whether comparison signal of loose contact of current drives end; And

The level translator switch module will carry out the conversion of level to the output signal of voltage sample comparison module and current sample comparison module this two, make its signal meet the level signal of CPU, and the signal after the level conversion is exported to CPU; And

CPU counts the signal of level translator switch module output, thereby determines the situation whether current p-wire exists loose contact; And

Display, the output signal of reception CPU shows the situation that p-wire contacts.

Adopted such scheme; The utility model has solved the offset issue of the data result that present impedance measurement aspect causes owing to the p-wire loose contact; The measuring error that has significantly reduced therefore problem like this and caused; Improve the qualification rate of the examination and test of products, improved work efficiency, thereby reduced job costs.Select for use a kind of and the signal signal source different frequency, thereby distinguish any road p-wire loose contact.

Description of drawings

Fig. 1 is the circuit block diagram of the utility model;

Fig. 2 is the circuit theory diagrams of corresponding diagram 1;

Fig. 3 is another embodiment of reference signal source module

Fig. 4 is another embodiment of level translator switch module;

In the accompanying drawing, 1 is the signal amplification module, and 2 is the reference signal source module, and 3 is the voltage sampling signal synthesis module; 4 is the voltage sample comparison module, and 5 is the current drive signal module, and 6 is the current sample comparison module; 7 is the level translator switch module, and 8 is CPU, and 9 is display.

Embodiment

With reference to Fig. 1, the Meter Test line loose contact pick-up unit of the utility model comprises:

Signal amplification module 1, this signal amplification module carries out the amplification of signal amplitude with p-wire voltage sample end signal; And reference signal source module 2, this reference signal source module provides a ripple that exchanges with the voltage sampling signal different frequency; And voltage sampling signal synthesis module 3, the signal of the signal amplification module that receives and the signal of reference signal source are synthesized, obtain voltage sample end composite signal; And voltage sample comparison module 4, the signal of the voltage sampling signal synthesis module output positive and negative voltage with a setting is compared, thereby obtain the whether comparison signal of loose contact of voltage sample end; And be the current drive signal module 5 of the sampled signal of p-wire current drives end; And current sample comparison module 6, the current sampling signal of the current drive signal module output positive and negative level with a setting is compared, thereby obtain the whether comparison signal of loose contact of current drives end; And level translator switch module 7, will carry out the conversion of level to the output signal of voltage sample comparison module and current sample comparison module this two, make its signal meet the level signal of CPU, and the signal after the level conversion is exported to CPU; And CPU8, the signal of level translator switch module output is counted, thereby determined the situation whether current p-wire exists loose contact; And display 9, the output signal of reception CPU shows the situation that p-wire contacts.Make detailed description in the face of the concrete structure of each module down:

With reference to Fig. 2; Signal amplification module 1 comprises the first operational amplifier U1, the second operational amplifier U2; Be connected to the in-phase input end of the first operational amplifier U1 after one first capacitor C 1 and 1 series connection of first resistance R, the other end of first capacitor C 1 is unsettled, receives during use to come from p-wire voltage sample end signal; Second resistance R 2 and the 3rd resistance R series connection back one end ground connection, the other end is connected between first capacitor C 1 and first resistance R 1.The inverting input of the first operational amplifier U1 is connected with one the 4th resistance R 4, and the other end ground connection of the 4th resistance R 4 is connected one the 5th resistance (R5) between the inverting input of the first operational amplifier U1 and output terminal.The inverting input of the second operational amplifier U2 is connected with an end of the 6th resistance R 6, and the other end of the 6th resistance R 6 connects the output terminal of the first operational amplifier U1, is connected one the 7th resistance R 7 between the inverting input of the second operational amplifier U2 and the output terminal.

With reference to Fig. 2, reference signal source module 2 comprises reference signal source, charge-discharge circuit and Hi-pass filter, and charge-discharge circuit connects the output terminal of reference signal source, and the input end of Hi-pass filter connects the output terminal of charge-discharge circuit.It is 2kHz that reference signal source provides a frequency, and dutycycle is 33.3% 5V square-wave signal.Charge-discharge circuit is made up of resistance R 10, capacitor C 3, resistance R 11, capacitor C 4, and R10, capacitor C 3 constitute charge-discharge circuit for the first time, and resistance R 11, capacitor C 4 constitute charge-discharge circuit for the second time, and Hi-pass filter is made up of capacitor C 5 and resistance R 12.When the reference signal source input signal, capacitor C 3, resistance R 10 are discharged and recharged, be about 1V thereby obtain a minimum point, peak is the triangular signal about 3V.Through the signal after discharging and recharging for the first time, this signal is again to resistance R 11, and capacitor C 4 is carried out secondary and discharged and recharged, and makes signal more level and smooth.Through capacitor C 5, the Hi-pass filter that resistance R 12 forms is isolated DC level, thereby the 2kHz that obtains an about 50mV of effective value exchanges ripple Vf, and it is outputed to the in-phase input end of the 3rd operational amplifier U3.

With reference to Fig. 3, the reference signal source module can also adopt following circuit to substitute, and it comprises clock generator, is used to produce stable accurate clock signal; And frequency divider, the conversion of signals that will come from clock generator is square-wave signal output; And counter, the square-wave signal that will come from frequency divider converts the PROM address signal that frequency becomes the multiple relation into; And programmable read-only memory, the conversion of signals that will come from counter is the signal of counting the number of words; And D/A converter, the output conversion of signals that will come from programmable read-only memory is simulating signal output; And operational amplifier, the analog signal conversion that will come from D/A converter output is a ladder sine wave; And low-pass filter, the ladder sine wave that operational amplifier is exported converts sinewave output into.The working method of this replacement circuit is: the high stable precision interval clock signal that produces from the 7.68MHz clock generator adds to the frequency divider input; Export the square wave that a frequency is 20F (F is a frequency test signal); Obtain the PROM address signal that frequency becomes the multiple relation through counter again, in the programmable read-only memory stored 256 digital shape sinusoidal wave, under the address signal effect; The digital quantity of output is delivered to 8 D/A converters; Be the current signal amplitude of being transformed to of D/A converter output the ladder sine wave of 10Vp～p to the maximum through operational amplifier, this sine wave promptly obtains a standard sine wave through low-pass filter.

Voltage sampling signal synthesis module 3 comprises the 3rd operational amplifier U3; The in-phase input end of the 3rd operational amplifier U3 is connected with the output terminal of reference signal source module 2; The inverting input of the 3rd operational amplifier U3 is connected with the output terminal of signal amplification module 1; Between the inverting input of the 3rd operational amplifier U3 and its output terminal, be connected one the 8th resistance R 8, be connected with the signal amplification module through a feedback resistance R9 at the output terminal of the 3rd operational amplifier U3.

With reference to Fig. 2; Voltage sample comparison module 4 comprises the first comparer U4, the second comparer U5; The inverting input of the first comparer U4 is connected with the voltage of a negative 5V through the 13 resistance R 13; The 14 resistance R 14 of a ground connection is connected with the inverting input of the first comparer U4, and the in-phase input end of the first comparer U4 is connected with the output terminal of voltage sampling signal synthesis module.The inverting input of the second comparer U5 is connected with the output terminal of voltage sampling signal synthesis module; The in-phase input end of the second comparer U5 is connected with the voltage of a positive 5V through the 15 resistance R 15, and the in-phase input end of the second comparer U5 is also through the 16 resistance R 16 ground connection.

With reference to Fig. 2, current drive signal module 5 comprises first charge-discharge circuit, and second charge-discharge circuit that is connected with this first charge-discharge circuit.First charge-discharge circuit is made up of the 6th capacitor C 6 and the 21 resistance R 21; First charge-discharge circuit is made up of the 7th capacitor C 7 and the 22 resistance R 22; The 6th electric capacity (C6) the back ground connection of connecting with the 21 resistance R 21, the 7th capacitor C 7 ground connection of connecting with the 22 resistance R 22.Likewise, discharge and recharge through the current drive signal of two-stage charge-discharge circuit to input, the current signal of output is comparatively level and smooth.

With reference to Fig. 2; Current sample comparison module 6 comprises the 3rd comparer U6, the 4th comparer U7; The in-phase input end of the 3rd comparer U6 is connected with a positive level through the 17 resistance R 17; The 18 resistance R 18 of a ground connection is connected with the in-phase input end of the 3rd comparer U6, and the inverting input of the 3rd comparer U6 is connected with the output terminal of current drive signal module 5.The in-phase input end of the 4th comparer U7 is connected with the output terminal of current drive signal module 5; The inverting input of the 4th comparer U7 is connected with a negative level through the 19 resistance R 19, and the inverting input of the 4th comparer U7 is also through the 20 resistance R 20 ground connection.

With reference to Fig. 2; Level translator switch module 7 comprises triode Q1, the 23 resistance the 23, the 24 resistance the 24, the 25 resistance 25, and the base stage of triode Q1 is connected with an end of the 24 resistance 24, an end of the 23 resistance 23 be connected power supply; The other end is connected with the 24 resistance; The collector of triode Q1 is connected with an end of the 25 resistance 25, and the other end of the 25 resistance 25 connects power supply, the grounded emitter of triode Q1.

With reference to Fig. 4, level translator switch module 7 can also adopt photoelectrical coupler to substitute.The anode that outputs signal to the optocoupler diode of voltage sample comparison module 4 and current sample comparison module 6.When comparator signal be+during the 5V high level, the optocoupler diode current flow, the conducting of optocoupler output terminal triode, the level signal of exporting to CPU is a zero level; When comparator signal be-during 5V, the optocoupler diode ends, optocoupler output terminal triode ends, exporting to cpu signal is high level.This shows the triode Q1 of this circuit in can perfect alternate figures 2.

The course of work of the utility model is following:

During the instrument operate as normal, test lead HC, HP, LC; LP all reliably is connected with measured piece, and the contact of p-wire is good, and at this moment, the output Vo of U3 is the interchange ripple of 1kHz; And signal amplitude is at V+, between V-, thus the first comparer U4; The second comparer U5 is output as high level, triode Q1 conducting, and the signal of exporting to CPU is a low level.Show that the p-wire contact is good.

When voltage sample end p-wire broke off, Vin did not have input, and first capacitor C 1 is floating empty; The output voltage V f of reference signal source forms positive feedback through the feedback resistance R9 on the 3rd operational amplifier U3, and the output signal exceeds the positive-negative power of amplifier, by cut the top become 2kHz ± square wave of 5V; This square-wave signal exceed setting+5V and-scope of 5V, thereby voltage sample comparison module 4 output results are the square-wave signal of 2kHz; This signal makes that triode Q1 can not conducting; Thereby the signal that makes triode export to CPU is the fixed frequency of a 2kHz, through CPU counting gained, breaks off thereby judge voltage sample end p-wire.

When current drives end p-wire breaks off, Vin (like Fig. 2) ground connection, the output electric signal Vo of voltage sampling signal synthesis module 3 is that a small-signal 2kHz exchanges ripple, and the scope of this electric signal is within ± 5V, and this signal deficiency is so that triode Q1 conducting.Yet the voltage Vin1 (like Fig. 2) that the electric current on the measured piece is sampled on range resistance has but produced sudden change because of the disconnection of current sample end p-wire; This signal and the positive level that is connected the 3rd comparer, and the negative level that connects the 4th comparer compares, and obtains the square-wave signal of a 1kHz; Be used to control the conducting of triode Q1; This signal is exported to CPU, through counting, detects current sample end p-wire and breaks off.

After breaking off when voltage sample end p-wire, $V02=(1-\frac{\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}7\&times;R5}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6\&times;R4})\&times;\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1,$ Here make R7 * R5=R6 * R4, so V02=0; Like this $\mathrm{Vo}=(1+\frac{R8}{Z_{c2}})\&times;V_f,$ Output signal frequency is the waveform of 2kHz.For making this signal exceed the scope of comparative level; Thereby can differentiate the problem that voltage sample end p-wire breaks off according to this, get R8=50k Ω, capacitor C 2=1uF here; Like this output amplitude of Vo reached ± 7.8V about; The power range that has exceeded the 3rd operational amplifier U3 is pushed up ± 5V so the output result cuts, thereby the 3rd operational amplifier U3 output this moment Vo signal is the square-wave signal of a 2kHz.

Show the utility model with derivation below:

With reference to Fig. 2, when the instrument operate as normal, test lead is all reliable to be connected.Vin is the 1kHz frequency, 6 millivolts of sine waves that effective value is following, and it amplifies through the first operational amplifier U1 through first capacitor C 1 $1+\frac{R5}{\mathrm{<figure-callout\; id="4"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}4}$ Doubly, obtain signal V01; And V01 and V1 obtain signal V02 through the amplification of the second operational amplifier U2, and relation does between it $V02=(1+\frac{R7}{R6})\&times;V1-\frac{R7}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6}\&times;V01,$ And $V01=(1+\frac{R5}{R4})\&times;\mathrm{Vin},$ Thereby $V02=(1+\frac{R7}{R6})\&times;V1-\frac{R7}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6}\&times;(1+\frac{R5}{R4})\&times;\mathrm{Vin};$ Because Vin is very little, so V1 mainly contains resistance R 3, feedback resistance R9 dividing potential drop forms, promptly in addition $V$ $1=\left(\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+R9}\right)\&times;\mathrm{Vo},$ So $V02=(1+\frac{R7}{R6})\&times;\left(\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+R9}\right)\&times;\mathrm{Vo}-\left(\frac{R7}{R6}\right)\&times;(1+\frac{R5}{R4})\&times;\mathrm{Vin};$ Amplification obtains Vo and V02 is through the 3rd operational amplifier U3, therefore has following relation again $V02=(1+\frac{Z_{C2}}{R8})\&times;V_f-\frac{Z_{C2}}{\mathrm{<figure-callout\; id="8"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}8}\&times;\mathrm{Vo},$ Thereby can push away in view of the above $[\frac{Z_{C2}}{\mathrm{<figure-callout\; id="8"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}8}+(1+\frac{R7}{R6})\&times;\left(\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+R9}\right)]\&times;\mathrm{Vo}=(1+\frac{Z_{C2}}{R8})\&times;V_f+\frac{R7}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6}\&times;(1+\frac{R5}{R4})\&times;\mathrm{Vin};$ The output signal of so final Vo is the composite signal of Vf and Vin, and signal frequency is 1kHz, amplitude and+5V and-5V between; So the final first comparer U4, the high electricity of second comparer U5 output, and this moment, current sampling signal Vin1 signal was the millivolt level; Signal frequency is 1kHz, amplitude V and-V between, so the 3rd comparer U6; The 4th comparer U7 is output as high level, and the output of final like this four comparers is high level, control triode Q1 conducting; Thereby the signal of exporting to CPU is a low level, shows that all p-wire contacts are good.

When voltage sample end p-wire broke off (loose contact), Vin did not have the signal input, and this moment first, capacitor C 1 was floating empty. $\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1=\left(\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+R9}\right)\&times;\mathrm{Vo},$ And $V01=(1+\frac{R5}{R4})\&times;\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1,$ Thereby $V01=(1+\frac{R5}{R4})\&times;\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+\mathrm{<figure-callout\; id="9"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}9}\&times;\mathrm{Vo};$ And $V02=(1+\frac{R7}{R6})\&times;V1-\frac{R7}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6}\&times;V01,$ Thereby $V02=(1+\frac{R7}{R6})\&times;V1-\frac{R7}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6}\&times;(1+\frac{R5}{R4})\&times;\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1,$ Derive thus $V02=(1-\frac{\mathrm{<figure-callout\; id="7"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}7\&times;R5}{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}6\&times;R4})\&times;\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1,$ Here make R7 * R5=R6 * R4, so V02=0; Like this $\mathrm{Vo}=(1+\frac{R8}{Z_{c2}})\&times;V_f,$ Output signal frequency is 2kHz; And since this moment Vo peak-to-peak value exceeded the positive-negative power scope of the 3rd operational amplifier U3; So pushed up by cutting ± square-wave signal of the 2kHz of 5V; The Vo of this moment exceeded ± scope of 5V, so the first comparer U4, the square-wave signal of second comparer U5 output 2kHz.When breaking off (loose contact) owing to the voltage sample end simultaneously, the current sample end still contacts well, and the current sample voltage Vin1 of this moment remains normal signal; So the 3rd comparer U6, the 4th comparer U7 output signal still is a high level, and it does not influence the first comparer U4; The output signal of the second comparer U5, the output signal of so final comparer is 2kHz, the square-wave signal of ± 5V; Its control triode Q1's can not conducting, thereby obtains a 2kHz, the square-wave signal of 0～5V; And output it to CPU, through counting, judge that this moment, voltage sample end p-wire broke off (loose contact).

When current sample end p-wire breaks off (loose contact), Vin=0, so this moment V01=0; So can push away $V02=(1+\frac{R7}{R6})\&times;\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1,$ And $\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">V</figure-callout>}1=\left(\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+R9}\right)\&times;\mathrm{Vo},$ So can get $V02=(1+\frac{R7}{R6})\&times;\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+\mathrm{<figure-callout\; id="9"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}9}\&times;\mathrm{Vo};$ And $V02=(1+\frac{Z_{C2}}{R8})\&times;V_f-\frac{Z_{C2}}{\mathrm{<figure-callout\; id="8"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}8}\&times;\mathrm{Vo},$ Can push away thus: $[(1+\frac{R7}{R6})\&times;\frac{R3}{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HDA0000101703510000011.png,HDA0000101703510000021.png"\; state="\{\{state\}\}">R</figure-callout>}3+\mathrm{<figure-callout\; id="9"\; label="R"\; filenames="HDA0000101703510000011.png"\; state="\{\{state\}\}">R</figure-callout>}9}+\frac{Z_{C2}}{R8}]\&times;\mathrm{Vo}=(1+\frac{Z_{C2}}{R8})\&times;V_f,$ This moment, Vo was the interchange ripple of a 2kHz, and signal amplitude is at V+, between the V-, thus the first comparer U4, the second comparer U5 is output as high level; Simultaneously, when DRIVE current drives end p-wire broke off, the current sample voltage signal changed, its amplitude exceeded V and-scope between the V; Thereby comparer the 3rd comparer U6, the 4th comparer U7 is output as a 1kHz, the square-wave signal of ± 5V; Whether the conducting of this signal controlling triode Q1, thereby obtain a 1kHz, the square-wave signal of 0 to 5V variation; And this signal exported to CPU, through counting, break off (loose contact) thereby judge this moment current sample end p-wire.

Claims (10)

1. a Meter Test line loose contact pick-up unit is characterized in that, comprising:

The signal amplification module, this signal amplification module carries out the amplification of signal amplitude with p-wire voltage sample end signal; And

Reference signal source module, this reference signal source module provide a ripple that exchanges with the voltage sampling signal different frequency; And

The voltage sampling signal synthesis module synthesizes the signal of the signal amplification module that receives and the signal of reference signal source, obtains voltage sample end composite signal; And

The voltage sample comparison module compares the signal of the voltage sampling signal synthesis module output positive and negative voltage with a setting, thereby obtains the whether comparison signal of loose contact of voltage sample end; And

Current drive signal module for the sampled signal of p-wire current drives end; And

The current sample comparison module compares the current sampling signal of the current drive signal module output positive and negative level with a setting, thereby obtains the whether comparison signal of loose contact of current drives end; And

The level translator switch module will carry out the conversion of level to the output signal of voltage sample comparison module and current sample comparison module this two, make its signal meet the level signal of CPU, and the signal after the level conversion is exported to CPU; And

CPU counts the signal of level translator switch module output, thereby determines the situation whether current p-wire exists loose contact; And

Display, the output signal of reception CPU shows the situation that p-wire contacts.

2. Meter Test line loose contact pick-up unit according to claim 1; It is characterized in that: said signal amplification module comprises first operational amplifier (U1), second operational amplifier (U2); Be connected to the in-phase input end of first operational amplifier (U1) after one first electric capacity (C1) and first resistance (R1) series connection; The inverting input of first operational amplifier (U1) is connected with one the 4th resistance (R4); The other end ground connection of the 4th resistance (R4) is connected one the 5th resistance (R5) between the inverting input of first operational amplifier (U1) and output terminal; The inverting input of second operational amplifier (U2) is connected with an end of the 6th resistance (R6); The other end of the 6th resistance (R6) connects the output terminal of first operational amplifier (U1), is connected one the 7th resistance (R7) between the inverting input of second operational amplifier (U2) and the output terminal.

3. Meter Test line loose contact pick-up unit according to claim 1; It is characterized in that: said reference signal source module comprises reference signal source, charge-discharge circuit and Hi-pass filter; Charge-discharge circuit connects the output terminal of reference signal source, and the input end of Hi-pass filter connects the output terminal of charge-discharge circuit.

4. Meter Test line loose contact pick-up unit according to claim 1, it is characterized in that: said reference signal source module comprises: clock generator is used to produce stable accurate clock signal; And

Frequency divider, the conversion of signals that will come from clock generator are square-wave signal output; And

Counter, the square-wave signal that will come from frequency divider converts the PROM address signal that frequency becomes the multiple relation into; And

Programmable read-only memory, the conversion of signals that will come from counter is the signal of counting the number of words; And

D/A converter, the output conversion of signals that will come from programmable read-only memory are simulating signal output; And

Operational amplifier, the analog signal conversion that will come from D/A converter output is a ladder sine wave; And

Low-pass filter, the ladder sine wave that operational amplifier is exported converts sinewave output into.

5. Meter Test line loose contact pick-up unit according to claim 1; It is characterized in that: said voltage sampling signal synthesis module comprises the 3rd operational amplifier (U3); The in-phase input end of the 3rd operational amplifier (U3) is connected with the output terminal of reference signal source module; The inverting input of the 3rd operational amplifier (U3) is connected with the output terminal of signal amplification module; Between the inverting input of the 3rd operational amplifier (U3) and its output terminal, be connected one the 8th resistance (R8), be connected with the signal amplification module through a feedback resistance (R9) at the output terminal of the 3rd operational amplifier (U3).

6. Meter Test line loose contact pick-up unit according to claim 1; It is characterized in that: said voltage sample comparison module comprises first comparer (U4), second comparer (U5); The inverting input of first comparer (U4) is connected with a negative voltage through the 13 resistance (R13); The 14 resistance (R14) of a ground connection is connected with the inverting input of first comparer (U4), and the in-phase input end of first comparer (U4) is connected with the output terminal of voltage sampling signal synthesis module; The inverting input of second comparer (U5) is connected with the output terminal of voltage sampling signal synthesis module; The in-phase input end of second comparer (U5) is connected with a positive voltage through the 15 resistance (R15), and the in-phase input end of second comparer (U5) is also through the 16 resistance (R16) ground connection.

7. Meter Test line loose contact pick-up unit according to claim 1, it is characterized in that: the current drive signal module comprises first charge-discharge circuit, and second charge-discharge circuit that is connected with this first charge-discharge circuit.

8. Meter Test line loose contact pick-up unit according to claim 1; It is characterized in that: said current sample comparison module comprises the 3rd comparer (U6), the 4th comparer (U7); The in-phase input end of the 3rd comparer (U6) is connected with a positive level through the 17 resistance (R17); The 18 resistance (R18) of a ground connection is connected with the in-phase input end of the 3rd comparer (U6), and the inverting input of the 3rd comparer (U6) is connected with the output terminal of current drive signal module; The in-phase input end of the 4th comparer (U7) is connected with the output terminal of current drive signal module; The inverting input of the 4th comparer (U7) is connected with a negative level through the 19 resistance (R19), and the inverting input of the 4th comparer (U7) is also through the 20 resistance (R20) ground connection.

9. Meter Test line loose contact pick-up unit according to claim 1; It is characterized in that: said level translator switch module comprises triode (Q1), the 23 resistance (23), the 24 resistance (24), the 25 resistance (25); The base stage of triode (Q1) is connected with an end of the 24 resistance (24); One end of the 23 resistance (23) be connected power supply, the other end is connected with the 24 resistance, the collector of triode (Q1) is connected with an end of the 25 resistance (25); The other end of the 25 resistance (25) connects power supply, the grounded emitter of triode (Q1).

10. Meter Test line loose contact pick-up unit according to claim 1, it is characterized in that: said level translator switch module is a photoelectrical coupler.

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