Capacitance and Fluke 87

[plongson]

I'm having a heck of a time. I cannot get a cap reading from my Fluke 87. I'm not testing small caps but start/run caps for blower fans, AC compressors and such...5,10, 55 MFD's etc.
I'm setting per the users manual and after the decimal moves along I just get "OL". I've tested the same caps on another meter and get readings showing the caps are good.
What am I doing wrong???

 

[SLK001]

Maybe the caps are out of range for the Fluke. What does it say the maximum cap that can be measured is?

 

[mksj]

You need to select capacitance by pressing the yellow button and selecting capacitance from the menu, the default otherwise is ohms if you are just selecting it with the rotary switch.

 

[plongson]

THANKS!! I'm gonna get back on it and experiment!

 

[den-den]

I use a Fluke 87, it will not measure very much capacitance. I don't remember the limit but at least some (if not all) the values you listed exceed what mine will read.

 

[SLK001]

The Fluke 87 will only measure to 5.00 uF. A 5.10 uF cap will give you the OL, or over-range display.

 

[plongson]

Well, that answers it...! Super thanks...

 

[ericc]

If it is near 5 uF, put another capacitor in series and back out from the formula. If it is much larger, you can measure it with an analog voltmeter with at least 100K input resistance.

 

[rabler]

IIRC Fluke gives a way in their manual to estimate the capacitance of larger caps by timing how long it takes to reach overload on one of resistance ranges.