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Current Measuring Device

IP.com Disclosure Number: IPCOM000078617D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Sabatterie, R: AUTHOR

Abstract

This device enables the measurement of a direct or rectified alternative current, by shifting the magnetic hysteresis cycles.

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Current Measuring Device

This device enables the measurement of a direct or rectified alternative current, by shifting the magnetic hysteresis cycles.

Generator G supplies a square-wave voltage which feeds control circuit 1 of ferrites 2 and 3, the windings of the control circuit being in opposition. Conductor 4 passes through the ferrites in the same direction. Current to be measured, Im, flows through the conductor 4. Detecting circuit % includes two windings in series, i.e. one winding for each ferrite.

Normally, when circuit 1 is operated and current Im to be measured is null, sensing current Is should be null. In practice, since the hysteresis cycles of both ferrites are not identical and as a function of the temperature, a current Is different from zero appears, even when Im is null. However, each hysteresis cycle is effectively symmetrical with respect to its center. It results that the voltages calculated at half a period of interval are in opposition and that their algebraical sum is null. If current Im is different from zero, the voltages are no longer in opposition and their algebraical sum will be proportional to current Im.

Thus, generator G also controls a sampling control circuit 6 through an integrator circuit RC, the circuit C delivering two pulses shifted by half a period. These pulses are supplied to field-effect transistors (FET's) 7 and 8, effectively sampling the signal issued from detecting circuit 5 which is amplified by amplifier
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