Products > Test Equipment
AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
Fungus:
--- Quote from: bobale on January 15, 2020, 06:53:10 am ---Question is: will I ever be able to get back the accuracy with 1% resistors (can't really find any better locally), should i try calibration procedure, or should I scrap the multimeter?
--- End quote ---
You could buy a load of cheap 1% 4.7M resistors and pick out the two that are best matched.
OTOH the calibration will probably be done with of error so you might have to find two that are slightly mismatched, by just the right amount to make it work (put a pot in series with one of them and dial it in to find the exact ratio needed). :popcorn:
Also think about getting a Fluke 101 for measuring things like that in the future.
bobale:
I rarely need to measure that high voltage, CCLF backlit monitors are on the way out anyway.
Thanks for the suggestion. I have 4.7M, 5.1M and 10M, 10pcs each, and will combine them in some way to get the it to measure correctly. As far as I'm aware, those two 5M resistors (R29 and R30) are only for measuring voltage, right? Other things shouldn't be affected?
Fungus:
--- Quote from: bobale on January 15, 2020, 09:51:09 am ---As far as I'm aware, those two 5M resistors (R29 and R30) are only for measuring voltage, right? Other things shouldn't be affected?
--- End quote ---
Hang on...
Looking at your photo closely I see they're the input protection resistors (leading to the PTC). It's not a voltage divider at all, it's just a 10M (approx) resistance to give a high impedance input and I don't think they're high precision at all. Maybe your problem is simply that you put in a much higher value.
bobale:
Here's higher res photo in the attachment. This should be diveder as it is going straight to the chip, not to the PTC.
HKJ:
--- Quote from: Fungus on January 15, 2020, 11:55:35 am ---Hang on...
Looking at your photo closely I see they're the input protection resistors (leading to the PTC). It's not a voltage divider at all, it's just a 10M (approx) resistance to give a high impedance input and I don't think they're high precision at all. Maybe your problem is simply that you put in a much higher value.
--- End quote ---
The 10Mohm resistors are always part of the input voltage divider and is used in volt AC/DC, it can also be used in other ranges, but usually a about 1Mohm input resistor is used for them and that resistor is not used in a voltage divider only as protection.
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