SU566190A1 - Resistance metering apparatus - Google Patents

Description

one

The invention is intended for use in various devices for measuring resistances, particularly in electrical measuring technology.

A device for measuring resistances is known, containing an EMF source, exemplary resistors connected in series with switches, an operational amplifier whose feedback circuit includes a measured resistivity and a voltage ratio meter whose first input is connected to a measured resistance. l.

When measuring resistances in a large range, a set of model resistances switched by keys is used as a known resistance.

The advantage of the circuit is the ability to measure resistances in a large range of values, the measured value being associated with the resistance value by a linear ratio.

The disadvantage of the scheme is not high enough accuracy and naae.

Thus, the variation of the transient resistances of the keys connected in series with the model resistors causes a change in the scale of the transformation and introduces an error in the measurement result.

The reliability of the circuit is low due to the use of electromechanical switching elements as kdyuchy. Reliability increases when they are replaced by MOSFETs, but this increases significantly; measurement error due to the finite values of resistances of closed and open states of keys.

To increase the reliability of the device without reducing the accuracy of measurements, it is equipped with a switch, a control unit and a storage device, one output of which is connected to the second input of the voltage ratio meter, the EMF source and reference resistors through the KOMNiyTaTop, and the control unit is connected to switches and a switch other storage device source

EMF and the third entrance and the amrvtep ratio.

The drawing is a diagram of the proposed device.

 contains exemplary key resistors (vodvvvk emf 7, as measured by resistance to, | plugged in four clamping cxeuBs current terminals 9 and Yu, potential terminals 11 and 12, operative usypvtel 13, grounded input

14electric amplifier, voltage ratio meter 15, low-potential outputs 16–16 o 6 times Y1 resistors 1–3, respectively, switch 19, switch keys 2028, memory

29 and control unit AOR.

The device works as follows

When the device operates at the first measurement limit, block 30 closes the keys 4, 27, 28 and opens the keys 5, 6, 26. In the absence of mixing, the amplifier 13 is sufficiently large enough to increase its gain and the input resistance of the meter

15, the voltage U g on one of its inputs is determined by the relation where is the resistance between the low-potential output of resistor 1 () and the potential output of the measured resistance 8 (I) connected to the input of the amplifier 13. The device has two cycles of operation. In the first cycle, the keys 2O and 21 are closed and the keys 22-25 are open. In this case, the device 29 through the closed switches 2O and 21 is charged to the voltage of resistor 1 (R. In the second cycle, the keys, 21 are opened, and the keys 24 and 25 are closed, Mouth, the device 29 is connected to the second input of the voltage ratio meter 15, the indication of which is determined by the shape-MULOY. Thus, the indication of the device does not depend on the resistance value f.

The error introduced into the measurement result of leakage currents from source 7 through resistors 2i 3 and open switches 5, 6 is eliminated at the first measurement limit by closing low-potential leads of resistors 2 and 3 to grounded input 14 of operational amplifier with switches 27 and 28. The device operates similarly for the rest of the measurement limits. If, among the resistors 1-3, there are low impedance, and the currents passing through the keys 26-28 are large, it is advisable to run them on bipolar transistors that have the smallest resistance of the closed state among the electronic keys. In the remaining cases, they can be performed both on bipolar and field trasistor Hbix.

Claims (1)

Thus, the proposed device has a significantly higher accuracy and reliability when measuring resistances in a wide range of measured values. Claim device A device for measuring resistances containing an EMF source, exemplary resistors connected in series with keys, an operational amplifier whose feedback circuit includes a measured resistance in a four-terminal circuit and a voltage ratio meter whose first input is connected to a measured one. resistance is characterized in that, in order to improve device reliability without reducing measurement accuracy, it is equipped with a switch, a control unit and a storage device, one One of which is connected via a switch: to the second input of the voltage ratio meter, the source of electromotive force and reference resistors, and the control unit is connected via keys and switch to another output of the memory device, the source of the electromotive force and the third input of the ratio meter. Sources of information taken into account in the examination: 1. USSR Copyright Certificate No. 159224 cells & O1 T 27 / OO, 29.03.1963.