SU1009676A1 - Device for measuring welding current amplitude - Google Patents

Description

the gate is connected to the output of the delay line, the output of the clock pulses is connected to the key output, and the output of the initial setpoint pulses is connected to the output of the generator of single pulses, the first and second inputs of the synchronizer are connected to the inputs of the second and first comparator. respectively.

The invention relates to the control of resistance welding mode and can be used to measure the amplitude values of the welding current. A device for measuring the amplitude of the welding current is known in which the extraction of the amplitude of the welding current is made by measuring and storing the signal at the time the derivative of the welding current passes the non-cut zero C1. However, when welding on low-frequency and direct-current machines, determining the moment the derivative passes through zero is difficult which leads to an error in the measurement of the welding current amplitude. This is due to the fact that the welding current impulse has a rather flat front, characteristic especially with a long impulse duration, as well as the fact that during the current rise time there may be a tendency to decrease it. A device for measuring the amplitude of the welding current, containing a memory capacitor, is charged through the diode to the highest voltage applied to it during the passage of a welding current 2 3-. The voltage is measured by a high impedance measuring instrument. However, these devices have a significant measurement error. This error is introduced by the memory circuit consisting of a diode and a capacitor. Since the circuit has a certain time constant, the voltage across the capacitor depends on the duration of the welding current pulse. In addition, the nonlinearity of the current-voltage characteristic of the diode affects the measurement results. With a decrease in the applied voltage, the direct resistance of the diode increases dramatically, and the time constant of the discharge target of the storage capacitor increases, consequently, the voltage across the capacitor also decreases in comparison with the amplitude value. The aim of the invention is to improve the accuracy of measuring the amplitude of the welding current. The goal is achieved by the fact that a known device for measuring the amplitude of the welding current contains a current sensor, a memory unit, a measuring unit and an information reading unit in which the input of the measuring unit is connected to the output of the current sensor and the output of the memory unit is connected to the information input of the node information reading, additionally equipped with a selector, buffer register, comparison circuit, setpoint storage unit, decoder, coincidence circuit, subtraction unit, synchronizer and electrode compression force sensor c ;;, while the information inputs of the selector are connected to the output of the measuring unit and the output of the buffer register. The output of the selector is connected to the information input of the memory unit, and its control input to the output of the decoder. The output of the memory unit is connected to the information input of the buffer register and the input of the subtraction unit, the second input of which is connected to the output of the measuring unit and the output to the first input of the comparison circuit. The second input of the comparison circuit is connected to the output of the setpoint storage unit, its direct output is connected to the first input of the decoder, and the inverse is connected to the second input of the decoder and the first input of the coincidence circuit, the output of which is combined. not connected to the control input of the information reading unit, the synchronizer having an output of information read pulses associated with the second input of the coincidence circuit, a clock output associated with the control inputs of the subtractor, the buffer register and the memory block, the output of clock pulses, associated with the control input of the measuring unit, and the output of the initial pulses. setpoints associated with a memory block erase input. In addition, the two inputs of the synchronizer are associated with a date, a current ticker, and a sensor / force of electrodes. The synchronizer contains two compressors, a clock pulse generator, a single pulse generator, a key, a trigger and a delay line; wherein the output of the first comparator is connected with the input of the generator of single pulses, the output of which is connected with the input O of the flip-flop. The output of the second comparator is connected to the control input of the key and to the trigger input 1 Information key input is connected to the generator, clock pulses, and the output is connected to the input of the delay line, and the synchronizer information pulse output is connected to the trigger output, synchronizer clock output associated with the output of the delay line, the output of the clock pulses - with the output of the key, and the output of the pulses of the initial setpoint - with the output of the generator of single pulses. In this case, the first and second inputs of the synchronizer are connected with the inputs of the second and first comparators respectively. In FIG. 1 is a block diagram of the device; in fig. 2 is a block diagram of a synchronizer; Fig, 3 is a diagram of the operation of the device. The output of current sensor 1 is connected to the input of measuring unit 2 and the first input of synchronizer 3, the second input of which is connected to the signal circuit of the sensor for compressing the electrodes, not shown in the diagram; the output of the measuring unit 2 is connected to the first inputs of the subtraction unit 4 and the selector 5- The second input of the selector is connected to the upstream input of the buffer register 6, and the output of the selector is connected to the input of the memory unit 7. The output of the memory unit is connected to the input of the buffer register 6, the second input of the subtraction unit k and the input of the information reading unit 8. The first input of circuit 9 is compared to the output of the L subtractor, and its second input is connected to the setpoint storage unit 10. The direct inverted outputs of the comparison circuit 9 are connected to the input of the decoder 11, the output connected with the control circuit of the selector 5. In addition, the investment output of the comparison circuit 9 is connected to the first input of the matching circuit 12. The output of the coincidence circuit 12 is connected to the control circuit of the information reading unit 8. The communication circuits connect the synchronizer 3, respectively, to the second input of the matching circuit 12, the control inputs of the blocks A, 6.7 to the control input of the measuring unit 2 and the erase input of the memory block 7. In the synchronizer 3, the inputs of the comparator, the tori 17 18 are connected to the current sensor 1 and the sensor for compressing the electrodes. The output of the comparator 17 is connected to the input of a single generator 19, pulses, the output connected to the input O of the trigger 20. The output of the comparator 18 is connected to the control circuit of the switch 21 and the input 1 of the trigger 20, the information input of the key 21 is connected to the generator 22 of clock pulses and its output is with the input of delay line 23; The single trigger output 20 of the delay line 23, the key 21 and the generator .19 single impulses are connected to the first, second, third and fourth outputs of the synchronizer 3, respectively. The operation of the device is explained by the diagram. The following symbols are used on it: C 13 C 16diagram of signal changes on chains 13 16 of synchronizer connection 3, respectively; C 9 is the signal change diagram at the forward output of the comparison circuit 9 and C 18 at the output of the comparator 18 of the synchronizer 3B mbment tQ of electrode compression, the comparator 17 of the synchronizer 3 is triggered. A signal at its output starts the generator 19 of single IM pulses. The device elements are set to zero, the memory block 7 is cleared. When the welding current is switched on at time t, the comparator 18 is triggered. A negative switch 21 opens the key 21 at its output. The clock pulses from the generator 22 are fed to the input of the control unit I of the measuring unit 2 and through the line 23 of the delay to the control inputs of the subtractor k register 6 and block 7pam tee. The process of welding current measurement begins.

The measurement of the amplitude value of the welding current is based on the fact that the measured value of the signal is memorized; the current value of the signal is compared with that stored in memory A. and determining the increment of the first over the second, i.e. calculate the value of L A - A, | . With a positive increment of the current signal banner, under the condition where E is a given value, the contents of the memory block change, i.e. write to it the result of the last measurement. Otherwise, the contents of the memory block are not changed.

Comparison of the results of measurements made at two successive moments of the measurements specified by the clock generator 22 clock pulses of the synchronizer 3 is performed by the subtraction unit 4. The comparison of the value of L with E formed in the storage unit 10 of the setpoint is made by the circuit 9. At D 6, a high level of the signal is formed at the forward output of the comparison circuit 9, and on the inverse low. In this case, the falling edge of the pulse C H information from the output of the measuring unit 2 is recorded in the memory unit 7. At the same time, the result of the previous measurement stored in memory block 7 is deleted.

B some time point tj the measured value of the welding current A c is less than the previous A. The result of the comparison leads to the rewriting of the contents of the memory block 7 by reading the code from the buffer register 6, intended for intermediate storage of information. The numbers from memory block 7 are written into the buffer register 6 and subtraction block k, as well as from measurement block 2 to subtraction block k, on the leading edge of pulse C 1. The memory block 7 is connected to one of the two the channels of the measuring unit 2 or the buffer register 6 is performed by the selector 5; The selector 5 controls the decoder 11 in accordance with the combination of the | on channels in the forward and inverse outputs of the comparison circuit 9.

The measurement process continues until the end of time of the welding current pulse (t) - By a positive voltage drop at the output of the comparator 18 of the synchronizer 3, the trigger 20 is set to one. This allows information 8 to be read out from memory block 7. The elements of information readout node 8 are a digital indicator or a digitizer unit - display the amplitude value of the signal recorded during the pulse current of the welding current.

The accuracy of measuring the amplitude of the welding current by the device is determined by the frequency of the input signal and the accuracy of the analog-digital conversion of the signal by the measuring unit.

The use of the device is most appropriate in digital measuring systems, in particular, in systems of the lower level of hierarchical automated process control systems for welding.

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Ф91.1

FIG. J

Claims (2)

(57> 1. A DEVICE FOR MEASURING A WELDING CURRENT AMPLITUDE, comprising a current sensor, a memory unit, a measuring unit and an information reading unit, the input of the measuring unit being connected to the output of the current sensor and the output of the memory unit connected to the information input of the information reading unit, characterized in that, in order to increase the measurement accuracy, a selector, a buffer register, a comparison circuit, a set storage unit, a decoder, a matching circuit, a subtraction unit, a synchronizer and an electrode compression force sensor are added to it, p In this case, the information inputs of the selector are connected to the output of the measuring unit and the output of the buffer register, the output of the selector is connected to the information input of the memory unit, and its control input is connected to the output of the decoder, the output of the memory unit is connected to the information input of the buffer register and the first input of the subtraction unit, the second input which is connected to the output of the measuring unit, and the output to the input of the comparison circuit, the second input of the comparison circuit is connected to the output of the setpoint storage unit, the direct output of the comparison circuit is connected to the first the decoder, and the inverse version, to the second input of the decoder and the first input of the match circuit, the output of which is connected to the control input of the information reading unit, the synchronizer having the output of the information reading pulses connected to the second input of the match circuit, the sync output associated with the control the inputs of the subtraction unit, the buffer register and the memory block, the output of clock pulses associated with the control input i-g of the measuring unit, and the output of pulses of the initial setpoint associated with the input of erasing the block amyati; in addition, the first synchronizer input is connected to the output of the current sensor, and the second to the output of the electrode compression force sensor. 2. The device according to claim 1, characterized in that the synchronizer comprises a first and second comparators ^ clock generator _} a single pulse generator, a key, a trigger and an.-Delay line, wherein the output of the first comparator is connected to the input of a single pulse generator, the output of which * connected ς with input 0 of the trigger, the output of the second comparator is connected to the control input of the key and to input 1 of the trigger, the information input of the key is connected to the clock generator, and its output is connected to the input of the delay line, and the output of information read pulses synchronizer is connected to the trigger output, the output of the synchronization pulses is SU, 1009676 of the congestion is connected with the output of the delay line, the output of the clock pulses is connected with the key output, and the output of the initial setpoint pulses is connected with the output of the single pulse generator, while the first and second inputs of the synchronizer ’are connected to the inputs of the second and first comparators ·, respectively.