MEASURING THE STRAY CAPACITANCE OF SOLENOIDS WITH A TRANSMITTING AND A RECEIVING COIL

Air core solenoids, possibly single layer and with significant spacing between turns, are often used t o ensure low stray capacitance, as they are used as part of many senso rs and instruments. The problem of the correct esti mation of the stray capacitance is relevant both during design and to v alidate measurement results; the expected value is so low to be influenced by any stray capacitance of the external measuremen t instru ment. A simplified method is proposed that does not perturb the stray capacitance of the solenoid under test; the m ethod is based on resonance with an external capaci tor and on the use of a linear regression technique.