CS211477B1 - Resonant bridge connection for accurate mutual inductance measurement - Google Patents

Abstract

The invention relates to the connection of a resonant bridge for precise measurements of mutual inductance. The essence of the invention lies in the fact that one of the primary windings of a current comparator is connected in series to the branch of the bridge in which the primary winding of the measured mutual inductance is located. Its secondary winding is connected in series with a reference capacitor. The detection winding of the current comparator is connected to a zero voltage detector. An inductive divider is connected in parallel to the series combination of the reference capacitor with the secondary winding of the current comparator. The connection is intended in particular for the calibration of mutual inductances.

Description

(54) Resonance bridge connection for accurate mutual inductance measurement

The invention relates to the connection of a resonant bridge for accurate measurements of mutual inductance.

The principle of the invention is that one of the primary comparator windings is connected in series to a bridge branch in which the primary winding of the measured mutual inductance is connected. Its secondary winding is connected in series with a reference capacitor. The current comparator detection winding is connected to a zero voltage detector. An inductive divider is connected in parallel to the series combination of the reference capacitor with the secondary winding of the current comparator.

The wiring is designed especially for standardization of mutual inductances.

, 211477

BACKGROUND OF THE INVENTION The present invention relates to a resonant bridge for accurate inductance measurements with a current comparator.

Several types of resonant bridges containing mutual inductance are known. Rather than measuring mutual inductance! however, they are used for frequency measurement. To measure mutual inductance! they are less suitable. Their common disadvantage is that they cannot easily change the measuring range within wide limits and that they are not suitable for. Precise measurement of inductances of smaller values at low frequencies.

These disadvantages are eliminated by the use of a resonant bridge for accurate measurement of the four-strand inductance of the invention. It is based on the fact that one of the primary comparator windings is connected in series in a bridge branch in which the primary winding is inductive to one another. Its secondary winding is connected in series with the reference capacitor. The current comparator detection winding is connected to a zero voltage detector. An inductive divider is connected in parallel to the series combination of the reference capacitors with the secondary winding of the current comparator.

According to the invention, it is advantageous if a variable capacitor divider is connected in parallel to the inductive divider, the middle terminal of which is connected via a resistor to the middle terminal of the inductive divider.

By using a current comparator and an inductive divider according to the invention, a wide measuring range is achieved with high measuring accuracy.

The invention is illustrated in more detail by way of example with reference to the accompanying drawing.

In the circuit for accurate mutual inductance measurement according to the drawing, in the bridge branch in which the primary winding P is measured by mutual inductance, one of the primary windings PK, PK? The current comparator and regulating capacitance C _£ decade. A power supply U is connected to this series combination. The secondary winding SK is connected in series with a reference capacitor C _r and an inductive divider ID is connected in parallel to this series combination and a variable capacitor C ,, £ g is connected in parallel to this induction divider ID. . The intermediate terminal of the divider with variable capacitors C, Cg is connected via a resistor R to the middle terminal of the inductive divider ID. In parallel to the variable capacitors C ₂ , a secondary winding S is measured to measure mutual inductance! in series with the Dg detector.

The auxiliary voltage U _p is connected in parallel to the inductive divider IDs.

Auxiliary voltage regulating JJ _P in amplitude and in phase with the current flowing to the reference capacitance C _r is set so as to be 1/10, or. 1/100 of the current passing through the primary winding P of the measured mutual inductance. An indicator of this state is a current comparator K with a zero voltage detector 2 having two switchable windings PJCj and PK? and one secondary SK winding. One of the primary windings PK1, PKg has 10waves and one 10 times less windings than the secondary windings. If the detector D indicates zero voltage, the reference capacitance C, _{r of the} standard 10 is 10k or 100 times less than if the full current of the primary winding P of the measured mutual inductance would flow through it. In the measurement, the primary winding of the current comparator K is chosen, in which the voltage value on the capacitive standard C _{r is} closer to the voltage value _{n of the} secondary winding S of the measured mutual inductance, but not greater than this voltage. The bridge is balanced by an inductive divider ID and variable capacitors C, and Cg. In equilibrium, the Dg detector is de-energized and holds true

Μ = n. p / (a / ² _Cr ) where

M is the measured mutual inductance, n is the split ratio set on the divider ID. p is the current comparator K, «*> is the supply voltage frequency U of the bridge a

21147.7 2

C _r is the reference capacity value.

It will be appreciated that the separation ratio set in equilibrium on the induction divider IP is directly proportional to the value of mutual inductance U1. The appropriate proportionality constant can either be calculated as indicated, or it can be determined experimentally by measuring standards of mutual inductance of known values.

The wiring is designed especially for standardization of mutual inductances.

Claims (2)

SUBJECT OF THE INVENTION 1. A resonant bridge circuit for accurately measuring mutual inductance with four branches, characterized in that one of the bridge branches in which the primary winding (P) of the mutual inductance is connected in series is one of the primary windings (PKj, PKg) of the current comparator (K), whose secondary winding (SK) is connected in series with the reference capacitor (C _r ) and the detection winding (PK) of the current comparator (K) is connected to the zero-voltage detector (D,), (C _r ) with an inductive divider (IP) is connected in parallel with the secondary winding (SK) of the current comparator (K). Wiring according to claim 1, characterized in that a variable capacitor divider (C ,, Cg) is connected in parallel to the inductive divider (ID), the middle terminal of which is connected via a resistor to the middle terminal of the inductive divider (IP).