Simple Offset Elimination Technique for Two-Wire Measurements

Abstract

Measuring small inductors and capacitors can be challenging with the use of conventional LCR-meters that have a test frequency of 10 kHz or less. With a 10 nH inductor at 10 kHz, the impedance is only 6 mOhms, that is comparable to the resistance of the probes. At a frequency of 100 kHz, the impedance increases to 60 mOhms. On the other hand, a 1 pF capacitor at 10 kHz results in an impedance of 15 MOhms, which makes a capacitive connection between the probes noticeable and affects the measurement of impedance. This paper presents two case studies: an extraction the parasitic inductance of the two-wire probes using the HP4284A LCR-meter and HP16034E test fixture, and extraction of the parasitic capacitance using the LCR-Reader-R2 tweezer-meter. This method enables accurate measurements of sub-nH inductors and sub-pF capacitors using test frequencies below 300 kHz.