SU1599169A1 - Apparatus for measuring intensity of welding current - Google Patents

Abstract

The invention relates to a device for measuring current in a pulsed mode and can be used on resistance welding machines. The purpose of the invention is to improve the quality of the welded joint by improving the accuracy of welding current measurement and extending the measurement limits. The device contains a current sensor, the output of which is connected to the input of a controlled current source. The output of the latter is connected to a storage element, to which the input of a DC amplifier with a high-resistance input and an output of an electronic switch is also connected. A voltmeter is connected to the output of a DC amplifier with a high-resistance input, and an electronic switch input is connected to the synchronization circuits of the welding machine. During welding, the output voltage of the current sensor, directly proportional to the welding current, is fed to the input of a controlled current source. The output current of the latter is directly proportional to the signal from the current sensor and charges the memory element. The voltage across the memory element, directly proportional to the integral value of the welding current pulses, is amplified and indicated by a voltmeter. The total measurement error of the welding current when the device is operated does not exceed 0.2%. 3 il.

Description

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The invention relates to devices for measuring the current in a pulsed mode and can be used on resistance-welding machines.

The purpose of the invention is to improve the quality of the welded joint by improving the accuracy of welding current measurement and extending the measurement limits.

Figure 1 shows the functionalization scheme of the device; Fig. 2 shows a specific embodiment of the device; FIG. 3 shows diagrams explaining the principle of operation of the device.

The device (Fig. 1) contains a current sensor 1, a controlled current source 2, a storage element 3, a DC amplifier with a high-resistance input 4, a voltmeter 5, an electronic switch 6 o The elements of the device are connected in the following way.

The output of current sensor 1 is connected to the input of a controlled current source 2, the output of which is connected to memory element 3 to which is connected

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THKke input of DC amplifier with high-resistance input 4 and output of electronic key 6. To the output of DC amplifier with high-resistance input 4, a voltmeter 5 is connected, and the input of electronic key 6 is connected to the synchronization circuit of the welding machine.

A specific embodiment of the device is presented in FIG.

As a current sensor 1, an additional resistance introduced into the secondary circuit of the welding machine is used. The controlled current source 2 is made in the form of a preamplifier (transistor VT1) and a current mirror (transistors VT2 VT3).

The storage element J is a capacitor C. A DC amplifier with a high-resistance input A is made, for example, at the base of the K 140 UD 14 amplifier. A voltage meter 5 is used for measuring voltage (for example, B7-16). Electronic key 6 is made on the basis of the transistor VT4.

The device works as follows.

When welding is turned on, the output voltage of the sensor, which is directly proportional to the welding current, from current sensor 1 is fed to the input of a controlled current source 2, the output current of which is directly proportional to the instantaneous value of the input control voltage, charges memory element 3 (capacitor C). Thus, the voltage across the memory element 3 is directly proportional to the integral value of the welding current pulses. This voltage is amplified by a DC amplifier with a high-resistance input 4, at the output of which wave 5 is connected. At the end of the measurements, before the new welding cycle, the electronic switch 6, receiving a synchronization pulse from the welding machine, discharges the storage element 3. The discharge pulse can serve, for example, by changing the potential of the first anode of the lamp. L1 time controller RVE-7 when performing the first operation Compression.

On the basis of FIG. 3, the advantages of the proposed device are taken away from npoTotHnoM. Input

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The idealized pulse of the welding current 1 causes a voltage to appear on the memorized element in the proposed device according to a linear law (2), in the prototype by the exponent (3). Each specific value of this voltage represents information about the value of the welding current at the moment. The measurement error of this voltage (or after the amplifier) of the Linac causes an error in the determination of the welding current. AL t (in the proposed device) and 4t.3 (in the prototype). Obviously, the exponentiality curve of curve 3 (in the prototype) At is always greater than 417. and increases with increasing integration time. .

The proposed device has a high linearity and, with this accuracy, measurements of the welding current over a wide range — up to the voltage on the storage condenser — 5 and E — and, where E is the power supply voltage; UM is the voltage across the transistor VT3.

The total measurement accuracy of the current determines the accuracy of the voltmeter. Apply voltmeter 1-ggo klas0

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Sa, the total error in measuring the welding current strength is 0.2%.

Claims (1)

Invention Formula A device for measuring the strength of a welding current, comprising a welding machine, a current sensor, a memory element and a voltmeter, characterized in that it is improved in order to. nor is the quality of the welded joint due to increased measurement accuracy and extension of the measurement limits, it is equipped with a controlled current source, a DC amplifier with a high-resistance input and an electronic switch, while the current sensor is connected to the input of a controlled current source whose output and input . a DC amplifier with a high-resistance input and an output of an electronic switch are connected to a memory element, the input of the electronic switch is associated with the synchronization circuits of the welding machine, and a voltmeter is connected to the output of the DC amplifier with a high-resistance input. FIG. one FIG. 2 and 4t2 4t3 FIG ..