Reading capacitance on auto range

[dude]

On auto ranging capacidence, my meter reads pico f as nf, so just move the decimal over to  the right three places, right? I tried two different higher priced meters and they all read over 125p high. My namual meter with just holes, reads correct when I select 2000p. But both other meters read in nf and moving the decimal over to right gives pico f but the reading is always 125p more. What’s with thes auto ranging meters on capacidence? Only happens with caps that are pico f’s. Anyone else have any this problem? Reading all caps out of a circuit.  Al

[sluckey]

If your meter has a "relative" function use it to zero out the residual capacitance of your meter and leads.

[pompeiisneaks]

I thought I'd heard once that almost 0 multimeters are good at much under about 500-1000pF, and you should really get an LCR for that...

~Phil

[dude]

 I bought a Klein MM600, auto ranging or manual, nice meter. Had a relative function, did zero out the meter but again the readings were way high on every cap I checked that was in the 47 to 500 picofarad range. The Klein had two auto ranging readings, F and nF, every cap read perfect from 47uf to .005, the bright caps, 47p to 500p all read much higher. I took the Klein meter back and bought a cheap true RMS meter on ebay for $15, works great (might not last long for $15). The cheap meter read the same way as the Klein but again only on picofarads.


I have an old B&K with manual ranging, for caps it has holes on the meter and a picofarad setting, every bright cap reads within 10% of it's valve on the B&K. The same cap on the cheap meter with auto ranging for caps, read high, like a 510p reads .650nf or 650p.


Was just wondering if others had noticed this issue with auto ranging meters for capacitance...? Phil you say you say you heard of this before? Guess if I want a good meter buy a Fluke.


I'll just use the B&K for picofarad caps.


Thanks, al         

[pompeiisneaks]

I bought a Klein MM600, auto ranging or manual, nice meter. Had a relative function, did zero out the meter but again the readings were way high on every cap I checked that was in the 47 to 500 picofarad range. The Klein had two auto ranging readings, F and nF, every cap read perfect from 47uf to .005, the bright caps, 47p to 500p all read much higher. I took the Klein meter back and bought a cheap true RMS meter on ebay for $15, works great (might not last long for $15). The cheap meter read the same way as the Klein but again only on picofarads.


I have an old B&K with manual ranging, for caps it has holes on the meter and a picofarad setting, every bright cap reads within 10% of it's valve on the B&K. The same cap on the cheap meter with auto ranging for caps, read high, like a 510p reads .650nf or 650p.


Was just wondering if others had noticed this issue with auto ranging meters for capacitance...? Phil you say you say you heard of this before? Guess if I want a good meter buy a Fluke.


I'll just use the B&K for picofarad caps.


Thanks, al         

More that most dmm's even the really pricey Fluke 87 V can't read that low.  You need super short leads and other things to help avoid stray capacitance.  Most good LCR meter's have no leads and you slide the cap into slots on the device OR have very short well designed leads so they don't add capacitance. 

~Phil

[SILVERGUN]

I've had pretty good luck with one of these and find it accurate enough.
It comes with some short 2" clip leads. I really only use it when I'm double checking values as I install them.
https://www.amazon.com/Tenma-72-8150-TENMA_IT-72-8150-Capacitance-Meter/dp/B008DJSGYC