Why is it necessary to measure capacitance at different test frequency/voltages depending on the capacitance range? | FAQ

FAQ

How to measure capacitors/Test a Capacitors (2): Why is it necessary to measure capacitance at different test frequency/voltages depending on the capacitance range?

Capacitors

Multilayer Ceramic Chip Capacitors

MLCC with Dipped Radial Lead

A. The frequency settings for the meter are mainly depended on the parasitic of the component. In order to achieve more accurate reading of the component, measuring frequencies are directed away from the Self-Resonance Frequency (SRF) of the component. Industry users set the standards at different frequency points depending on the capacitance value (see Table 1). The capacitance over 10uF was considered in the range of Tantalum capacitors. Therefore, as the ceramic capacitance range began to increase into the Tantalum capacitor range, the industry adopted the frequency standard for Tantalum measurements into ceramic capacitors.

The applied voltage is also depended on the capacitance of the capacitor. Generally, the 10uF and under have applied voltage of 1.0 ± 0.2 Vrms. But over 10uF, the applied voltage is 0.5 ± 0.1 Vrms. High capacitance capacitors have very low impedance, therefore to supply enough current to make the measurement, the power supply needs more current than that supplied at 1.0 ± 0.2 Vrms. Therefore, by lowering the applied voltage, the power supply will be able to supply enough current to measure the high capacitance capacitor accurately.

Class Type	Capacitance	Frequency	Voltage
Class I	1,000pF and under	1MHz ± 10%	0.5 ～ 5 Vrms
Class I	Over 1,000pF	1kHz ± 10%	0.5 ～ 5 Vrms
Class II	10uF and under	1kHz ± 10%	1.0 ± 0.2 Vrms
Class II	Over 10uF	120Hz ± 20%	0.5 ± 0.2 Vrms

Table 1: Frequency and voltage settings for different capacitance range and class types.