Testing ceramic capacitors

**Chris Wilson** · Sun 11th Mar 2012, 22:23

Is there a reliable means of off board testing ceramic capacitors in the range 1pF to 0.1 uF? A lot of repair manuals cite several part numbers for ostensibly the same voltage rating and capacitance value ceramics, some even look exactly the same physical size. What might the differences be, tolerances? Thanks.

**5B4AJB** · Mon 12th Mar 2012, 00:11

There are only a very few cases where you cannot replace a capacitor with a similar value of higher Voltage rating.

In the past, I've had no problem replacing similar capacitance with higher Voltage rated capacitors.

If the capacitor to be replaced is an odd value, you can always "make up" the correct value by paralleling.

Wiki has a good page on capacitors.

**techiesteve** · Mon 12th Mar 2012, 06:56

The type of ceramic capacitor you'll come across will vary depending upon the age of the equipment its used in, and if its valve or semiconductor based. Most ceramic capacitors are reliable, unlike old paper dielectric capacitors from Hunts or TCC. They can short, measurable with a DVM, and their value can be checked with a capacitance or LCR meter. Beware accurately measuring small values, as the meter leads can add capacitance. Twist 2 wires together and you have a few pF. If you see a disk ceramic capacitor with a black dot on its top that normally indicates its an NPO type, usually found in VFO's or where ever frequency stability is required. A service manual will list the manufactures P/N originally used in manufacture, if you are replacing use the same type, voltage, tolerance or better.

**TI2-NA7U** · Sat 28th Apr 2012, 16:10

By the way, if you need a good capacitance/inductance checker I've found the one from Almost All Digital Electronics: http://www.aade.com/lcmeter.htm to be very reliable. I've used other cheapies and they were all over the map. This one from AADE is a kit, easy to build, and the price is great for what you get.

**SeanVN** · Tue 21st Aug 2012, 12:34

i would suggest a PC sound-card LCR meter.
http://www.sillanumsoft.org/ZRLC.htm
There are a few other ones out there as well. I have had good success with them except for very low value components. You also need to be careful about mains hum and hash getting into the sound card.
You could make a Bowes multvibrator with audio output. The frequency of oscillation only depends on the value of one capacitor and you would have to be very tone deaf not to be able to tell the difference between one capacitor value and another.