Low Power Measurement of Low Resistances by Simple Lock-In Amplifier

The paper is focused on unconventional low power method of measurement of very low resistances by means of a lock-in amplifier. There is explained the principle of a lock-in amplifier, design and implementation of simple lock-in amplifier with AD630 integrated circuit and implementation of a special shielded measuring chamber for sample connection as well. Subsequently, calibration process of the measuring system and comparative measurement on several samples of low value resistors is described. The results reveal ability to measure very low resistances by means of currents values that are many orders lower than in case of standard DC Ohm´s law method.