Mastech MS5308 Question

[Anson]

I just got my Mastech MS5308 LCR Meter and I am a bit confused. From what I have read most ESR meters test using a 100khz signal to allow in-circuit testing of caps right? Well I ma trying to use this meter set on capacitance and esr mode at 100khz and I am getting nearly always OL. And sometimes getting a reading that is very low value even on higher value caps. If I change the test frequency to 100 or 120hz many times I get a reading of 3.3 to 3.6mf. I am not sure what is going on. 

[elliott]

Most LCR meters can't do in-circuit tests. The Mastech has a test voltage of 500mV peak to peak, which can cause false readings due to turning on transistors, most testers capable of in-circuit readings are around 100mV. Keep in mind none of the in-circuit meters are particularly accurate either.

[ddavidebor]

On 100khz test voltage is lower, you can check with the scope.

[alm]

Measuring capacitance in circuit is not going to be accurate. ESR is usually slightly better, since you're only looking at orders of magnitude increases in ESR.

[Anson]

Ok makes sense. So in circuit testing I should only pay attention too the ESR reading. Should I always test in circuit at 100khz?

Also a few other silly questions. When would you use DCR? What is wastage factor or D? And what is quality factor or Q? I guess I'll ask about phase angle also when does that come into play?

[robrenz]

Download the Agilent impedance measurement handbook don't worry about getting all the math just try to get the basics from it.

[Anson]

Thanks! Just what I was looking for.