SU1504791A1 - High-ohmic simulator of electric resistance - Google Patents

Abstract

The invention relates to a measurement technique and can be used as a code-controlled electrical resistance measure used to test resistance measurement means. The purpose of the invention is to improve the accuracy of imitation. The simulator contains an operational amplifier 2 with paraphase outputs and external terminals 6,7,8. To achieve the goal, a high voltage voltage divider 1, a controlled resistor voltage divider 3, and a controlled multiresistor 4 with an electromagnetic screen 5 are introduced into the simulator. Due to the fact that amplifier 2 operates with zero common mode signals, the simulator's accuracy increases. The presence of the screen 5 in the multiresistor 4 eliminates the flow of parasitic currents along the multiresistor circuit. 1 il.

Description

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about

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The invention relates to a measurement technique and can be used as a code-controlled measure of electrical resistance used to test resistance measuring means.

The purpose of the invention is to increase the accuracy of the imitation of resistance, increase the permissible value of the measuring voltage.

The drawing shows an electrical structure of a high-resistance simulator,

The high impedance electrical resistance simulator contains a high voltage divider 1 voltage, an operational amplifier 2 with paraphase outputs, a controlled resistor voltage amplifier 3, a controlled multiplier 4 with an electromagnetic screen 5, the first 6, the second 7 and the third 8 external terminals.

High impedance electrical resistance simulator works as follows.

The simulator is connected to an isomer (not shown) by the first 6, second 7 and third 8 external leads so that the measuring voltage is applied between the first 6 and third 8 external leads, and the second external lead 7 is connected to that input a meter whose potential is maintained equal to the potential of the common point of the applied voltage. At the same time, the resistance reproduced by the high simulator is obtained between the first 6 and second 7 external signals. Since the potentials of the third B and the second 7 external leads are equal, we can write

2. 1and

Uo

17

(one)

Where cd is reproduced by simulator

resistance;

Ug is the voltage applied to the simulator from the side of the measuring circuit; 1 „is the current that flows through the simulated resistance to one of the inputs of the meter (to the current input). The voltage applied to the high-voltage voltage divider 1 is scaled. When the division factor is equal to M, we obtain the voltage at the output of the high-voltage divider 1 voltage, determined from the expression

and, uo / m,

(2)

where and,) is the input and output voltage of the high-voltage divider 1 voltage, respectively.

A voltage is applied between the first input and the output of the operational amplifier 2. Due to the high gain of the operational amplifier 2, the voltage 1 must be equalized between its inputs. In this case, a current is established in the second output circuit of the operational amplifier 2, which ensures the equality of the voltages between the inputs of the operational amplifier 2, which corresponds to the equality of the voltages at the outputs of the high-voltage divider 1 voltage and the controlled resistor voltage divider 3.

If the division ratio of the controlled resistor divider 3 voltage is equal to p, then the voltage U at the second output of the operational amplifier 2 can be determined from the expression

and - Ui Uo, ich .. ,, “.

(3)

 .

If the potentials of the third and the second 7 external leads are equal, which is provided by the meter, then the value of current 1 flowing through the controlled multiresistor 4 and determining the current through the resistance reproduced by the simulator can be determined by the formula

t and ° "KMR

(four)

where R., is the resistance value of the controlled multiresistor 4.

In accordance with (1), (4) reproducible three-clamp. high resistance simulator resistance R is equal to

To "rMK" (5)

In this case, RJ is completely determined by the parameters of the simulator nodes and does not depend on the magnitude of the input action,

Learn that, X, ..., X „, expression (5) can be written as follows:

RI, CO, X ,, ...,, (6) where, ..., 9,, ..., 9 depending on the dialed code at the input of the decade of the scale of the controlled resistor voltage divider.

From expression (6) it follows that by means of a three-clamp high resistance simulator with given M and R, resistance values from 0, l M R | q to MR can be obtained with a discreteness determined by the discreteness of the scale of the controlled resistor voltage divider 3.

The connection of the external screen of the operational amplifier 2 with the simulator common bus protects the operational amplifier 2 from leakage currents and improves the accuracy of the simulator, especially when playing large resistances. Due to the fact that the operational amplifier 2 works with zero common mode signals, the accuracy of the simulator is increased.

The presence of an electromagnetic shield 5 in the supervised multiresistor 4 eliminates the flow of parasitic currents through the controlled multiresistor circuit.

Claims (1)

Invention Formula A high-impedance electrical resistance simulator containing an operational amplifier with paraphase-outputs and an electromagnetic shield. 0 five 0 five 0 five connected to a common bus, characterized in that, in order to increase the accuracy of resistance simulation and increase the permissible value of the measuring voltage, a high-voltage voltage divider, a controlled voltage suppressor, and a multi-resistor with an electromagnet; The first output of the operational amplifier with para-phase outputs, the common output of the input and the output of the controlled resistor voltage divider are connected to the common bus, the signal input of the high-voltage voltage divider is the first external output of the high-resistance electrical resistance simulator, to the output of the high-voltage the voltage divider is connected to the first input of the operational amplifier with the paraphase outputs, the second input of which is connected to the signal input of the controlled resistor divider and to the first output of a controlled jfynb-thyristor, the second output of which is the second external output of a high-resistance electrical resistance simulator, and the screen is connected to a common bus, which is the third external output of a high-resistance electrical resistance simulator, the control input of a decade of scale is control a controlled resistor voltage divider input.