GB1416137A - Methods of and apparatus for measuring inductance - Google Patents

Abstract

1416137 Measuring inductance G M ETTINGER 19 Dec 1972 [1 Oct 1971] 45758/71 Heading G1U In a method of measuring an unknown inductance Lx, a voltage limiter Dl, D2 is connected across the inductance to limit the voltage across it to a value E, a pulse of maximum current I from a generator 1 is passed through the inductance, and the duration Tp of the voltage pulse appearing across the inductance is measured. For an inductance the voltage V across it is given by V = L di/dt. If V is held constant at a value E, and if the maximum value of the current i is I, then once the current through the inductance has reached the value I, di/dt becomes zero and the voltage across the inductance drops to zero. Thus the duration Tp of the voltage pulse appearing across the inductance is given by Tp = LI/E and is linearly proportional to the value L of the inductance. The duration Tp is determined by amplifying 2 the voltage across the inductance and gating Ti a constant current to a capacitor C for its duration. The maximum voltage appearing across the capacitor C is then extracted by a peak detector D3, Cl and displayed, via an appropriate D.C. amplifier, on a meter M. An alternative output 5, 6 is available direct from the gate T 1 .