GB2019015A - Measuring Number of Turns of a Toroidal Coil - Google Patents

Abstract

An energising coil 3 and a reference coil 6 each having a known number of turns are disposed about the toroidal core 1 and a voltage is induced across the reference coil and the coil under test by a voltage applied across the energising coil. A measure of the voltage induced across the reference coil 6 is derived and compared with a derived measure of the voltage induced across the coil under test 2 in a digital voltmeter 9 to derive a measure of the ratio of the number of turns of the coil under test to the number of turns of the reference coil. In this manner, errors due to voltage drop across the energising coil and associated iron losses are avoided. It is preferred to amplify the voltage induced across the reference coil by a first amplification factor 7, to amplify the voltage induced across the coil under test by a second amplification factor 10 and to make the product of the ratio of the first and second amplification factors and the number of turns of the reference coil equal to the response constant of the digital voltmeter so that the reading obtained directly represents the number of turns of the coil under test. <IMAGE>