SU151723A1 - Wide-range universal DC device - Google Patents

Description

Existing universal devices, such as A4-M2, VK-2, and others, designed to measure DC voltages, currents, and ohmic resistances, have a number of disadvantages. The input resistance of these devices is relatively small, the low sensitivity prevents measurement of thousandths of a volt, and when measuring resistance, the scale of the devices is nonlinear. With the aid of these instruments, large resistances (10 ohms) cannot be measured at reference voltages of the order of tens of volts.

The proposed universal measuring instrument makes it possible to extend the range of the measured values and measure large resistances. This is achieved due to the use of an electronic autocompensator with a high-resistance input in the device circuit.

FIG. 1 shows a block diagram of the device; in fig. 2 shows a voltage measurement circuit ranging from 3 to 100 volts; in fig. 3 is a circuit for measuring resistances ranging from 1 ohm to 1 mg; in fig. 4 shows a circuit for measuring resistances within 10-10 ohms.

The electronic autocompensator / is an AC amplifier with conversion using a DC-4 type vibrator converter of a DC signal to an AC input and a synchronous rectifier output. Due to the use of deep feedback, the input resistance of the auto-compensator circuit has a large value. The amplifier consists of three stages of voltage amplification and a cathode repeater with a transformer output and assembled on 6NZP and 6N2P lamps.

The excitation winding of the vibration transducer is powered by the sound generator 2 on a 6G1P lamp. The power of the amplifier and the generator is produced from the power supply unit 3 of the device, consisting of high-voltage

No. 151723-2 -

rectifier (ABC-80-260) and rectifier for feeding the lamp filament (D-303). Lamp circuits are powered by a constant voltage. The stabilizer is made on semiconductor devices P4A, P13 and D-808. Switching unit 4 is used to switch operating modes and measurement limits. The device is based on the use of a DC voltmeter with high sensitivity. Based on this, measurements of all the indicated values are carried out according to the method of measuring the voltage drop across the Resistance, including in the measuring circuit.

The measured voltage b is applied to the measuring circuit consisting of the resistance R and one of the resistances Ri - The voltage drop across one of the resistances - Ri is measured by a voltmeter 01M with a linear scale. In this case, the input resistance of the device is determined by the resistance of RU 220 mg. When measuring voltages ranging from 1 mV to 1, the input voltage is fed directly to the input of the autocompensator circuit.

The measured resistance Rx is connected to the source of the reference voltage in series with one of the model resistances. The auto-compensator measures the voltage drop across the sample resistance. The measurement limit is determined by the voltage Uoi - Uos of the reference source and the magnitude of the additional resistance Ri - RT. The reference voltage t / o is chosen to be 1, 3, 10, 30, and 100 volts depending on the magnitude of the resistance being measured. The reference voltage is stabilized by a stabilizer on a SG2P lamp and D-810 type zener diodes.

When measuring currents, the value of the reference (shunt input) resistance is chosen to be rather small. The described instrument has the following measurement limits:

1) DC voltage from 100 µV to 100 V over 11 ranges;

2) constant current from 10 A on the AND bands;

3) resistance from 0.1 to EVIL ohm on 18 ranges. The accuracy of the device in all measurement modes, voltage and

current is + 3% of the upper limit of measurement, and when measuring resistance, the error is ± 3% of the measured value on scales from 1 ohm to 3 g and + 5% of the measured value on scales from 3 to 300 g. The device is powered from the AC mains with a voltage of 110/127/220 V, and the power consumption is about 40 volts. When measuring the resistances, the proposed electronic autocamp allows to obtain a linear scale. In addition, the instrument may be used to measure the reverse resistance of silicon reference diodes at low dc voltages.

Subject invention

A wide-range universal DC device for measuring DC voltages, currents and ohmic resistances, having a switching unit, an electronic autocompensator, a sound generator and a power supply unit, characterized in that, in order to expand, ranges of measured values and possible. high resistance measurement, it uses an electronic auto-compensator with a high-resistance input.

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