SU1357896A1 - D.c.standard - Google Patents

Abstract

The invention can be used in precision devices for measuring direct currents. The purpose of the invention is to improve the accuracy of reproduction; direct current. The device contains a constant voltage source 1, a constant current comparator 5 magnetic flux indicator 8 and an adjustable constant current source 9. Performing an input winding of a DC comparator 5 with a given resistance and using it as a reference resistor reduces the influence of the resistance and leakage currents on the accuracy of the DC measurement. This, in turn, reduces the requirements imposed on the insulation of the interconnecting circuits and reduces the costs involved in the design and manufacture of the device and increases the reliability of the measurement. 1 il. 1X HI OE SP 00 co O)

Description

The invention relates to electrical measuring equipment and can be used in precision devices for measuring direct currents.

The purpose of the invention is to improve the accuracy of the reproduction of the direct current value.

The drawing shows a circuit diagram of a direct current circuit.

The DC measure includes a constant voltage source 1, which includes a Josephson junction 2, a bias current source 3, and a microwave voltage generator 4. A DC comparator 5 with an output winding 6, in which a resistor 7 forms an input winding, is inductively coupled to a null indicator 8 of the magnetic flux connected to a controlled DC source 9. The output of the latter is connected to the output winding 6 of the DC comparator 5. Leakage resistance and leakage points affect the circuits connecting resistor 7 and Josephson junction 3 (sources of leakage are not shown in the drawing). The connection circuits of resistor 7 and junction 2 are made of a superconductor, such as niobium. The wire of the resistor 7, which forms the input winding of the comparator 5, is made of an alloy having a low temperature coefficient of resistance at a temperature of 2-4 K, for example, an alloy based on silicon bronze,%: Cu 96; Si 3; Zn 1 .. The DC comparator 5 can be made in the form of a superconducting tube, inside of which there are winding wires. In this case, the tube is rolled up in the form of a ring in which one end of the tube covers the other, leaving the ring open electrically. A null magnetic flux indicator 8, made on the basis of a squid, is inductively coupled with the received ring.

The DC measure works as follows.

A constant voltage source 1 creates a current 1 in the primary winding 7 of the comparator 5 (source voltage 1, taken as the reference, RP is the resistance of the reference resistor 7. Voltage Uu (h / 2e) fn, where h is the constant n is Planck; e is the electron charge; f is the frequency of the microwave generator, n is the number of the step on the current-voltage characteristic of transition 2. The choice of the step is made by changing the current from source 3. Measured current 1 from the output of controlled source 9 is fed to the output winding 6 of the comparator 5. The TO and 1 currents create magnetic fluxes the effectiveness of KOTOpyjtx p . Gistriruets null indicator 8 magnetic flux When the equality ff current ratio is defined as the ratio of the number of turns of the windings:

5 D x the number of turns in the input 7 and output 6 windings, respectively. Equality f is achieved by adjusting the current of the output winding 6

0 by source 9 according to the control signal from the null indicator 8. It is also possible to adjust the current of the input winding 7 according to the control signal of the null indicator 8 (not shown) by changing

5 frequency generator 4 and / or the magnitude of the current of the source 3 at a constant value of the current of the source 9. The value of the measured current is defined as

T

 (Nj, / Nx) lIo / Ro due to the fact that the 0 resistor 7 forms the winding of the comparator 5, the effect of the leakage resistance changes just the amount of current consumption from the source 1, and the amount of current flowing through the transistor 7, defined as Uj, / Rp, remains unchanged; in addition, although the current flowing through the connection circuit of resistor 7 with junction 2 is no longer inaccuracy of resistor 7 by the amount of leakage current, it does not introduce an error in the determination of the measured value current, as the current in the connection circuit is not involved in comparison with current 1.

This leads to a reduction in the effect of leakage currents and leakage currents on the accuracy of measuring direct current, which reduces the requirements imposed on the isolation of the connecting circuits, reduces the cost of designing and manufacturing the device, and increases the reliability of measurements.

Claims (1)

Invention Formula 5 A measure of direct current, containing a source of direct voltage | and a reference resistor connected to its outputs, a DC comparator with input and output windings. 313578964 moreover, its output winding is due to the fact that, in order to keys adjustable current source, increase playback accuracy the control input of which is connected to a dc current, input the output of the null indicator of the magnetic by-winding comparator DC current inductively coupled to a company with a given resistance A direct current ramp, about tl and -i serves as a reference resistor.