Here's some results (I was given other duties
)
Firstly, the meter doesn't read anything under 0.1pF. I think that's a way of hiding the small readings when nothing is connected.
I find that mine reads 0.15pF or thereabouts even when zeroed. If I lift it above the bench, it reads 0.00 (therefore something less than 0.10).
Moving my hands cose to the probes changes the readings by up to 2 or 3 pF. Changing the position of the short test cables can change the reading by up to maybe 0.5pF.
The zeroing function clearly DOES NOT zero out the lead capacitance!!! If you zero it with a small capacitor connected, the meter reads pretty much the same as if you zero the meter then connect the cap.
The capacitors I used for the first test were five 0805 1.8pF caps connected in series using short lengths of wire wrap wire.
Here are some readings of these capacitors. There were 3 readings of each of the 5 caps.
Code:
2.17 2.43 2.09
2.36 2.31 2.06
2.36 2.25 2.03
2.34 2.12 1.89
2.29 2.16 1.92
The meter clearly reads high. The last colum contains tests were care was taken to keep the test leads separated as much as possible.
The capacitors were connected in series. Reading from end to end, the capacitors measured 0.28pF and 0.32pF (Thae calculated vaue would be about 0.36pF). These measurements required the leads to be much further apart than usual. If I ben the string of caps to allow the test leads to be as cose together as when I was reading a single cap, the value rose to 0.48pF.
During all of these tests, the value in the last digit varied by +/-1 or 2 digits (more if the leads could move)
I then grabbed a strip of 1nF 440VAC capacitors. these were also measured 3 times (results in pF
Code:
933 934 935
901 894 897
930 925 928
966 958 954
938 938 935
The results show it reading a ittle low, but interestingly the readings were rising. If I shorted out the cap, the value returned to a lower value (all of these were shortly after the shorted cap was connected).
Connecting a singe 0.1uF 275V X2 cap resulted in a reading of 100.2 or 100.3nF.
Lest you think I have very accurate capacitors, some 47nF caps read as 42.31nF and 42.48nF. The vaues vary by up to +/-5 in the last digit. My "good" meter reads these as 43.6nF and 43.9nF.
A dedicated capacitance meter reads 44.3nF and 44.7nF, 1.7pF, and 99.3n for the various capacitors.
I'm actually quite happy that all the meters do a pretty similar job