Will replacing a DMM's 9v battery wires, effect calibration? - Page 1
Forum section: electronics / repair

author: drdanke
author_rank: Contributor
timestamp: May 05, 2015, 04:03:56 am
content: I picked up a really nice, fairly recent manufacture, major brand name true RMS DMM, in brand new condition, at a garage sale for 15 bucks. As luck goes, it is indeed unused, but the original 9v alkaline battery has mildly exploded in the battery compartment. The actual battery connector wasn't corroded, but the wires are just starting to corrode a little. It's a very unusual battery connector, and I was able to complete disassemble the actual battery connector (it snaps apart), and the wires are directly soldered to the individual connector rings, so no problem restoring the connector itself to new condition. Now to my question...If I were to replace the individual red and black small gauge wires running from the PCB to the battery connector, with similar gauge wires of matching length, would this repair effect the factory calibration?I know, I should probably make the repair and get it recalibrated, but it's a $125-150 meter, and would probably be $100 for calibration.My DMM accuracy needs are very low, and just wanted something I could trust a little more than my old GB DMM, but don't know if I should replace the wires and use it, or just throw it away.What do you think, do the battery wires effect calibration?Oh, and I wasn't sure if this thread should have gone in the "Test Equipment" category.

author: BradC
author_rank: Super Contributor
timestamp: May 05, 2015, 04:07:50 am
content: Quote from: drdanke on May 05, 2015, 04:03:56 amAbsolutely. You need to determine the exact alloy the wires are made from, then strip them back and measure a strand with a micrometer and count the rest. The replacement wires need to be *identical* in every respect down to the chemical makeup and colour tint of the PVC insulation.<cough> No, of course not. Just replace it and be happy

author: helius
author_rank: Super Contributor
timestamp: May 05, 2015, 04:21:50 am
content: I don't see any way that it could affect cal. Consider that the voltage on an alkaline battery cell isn't fixed, it starts around 1.55V and slides downwards on a curve, continuously. So whatever resistive effects or thermal-emf comes from the battery wires is just overlaid on the basic instability of the battery itself. Just use normal copper wires though, other metals can have higher self-inductance.

author: IanB
author_rank: Super Contributor
timestamp: May 05, 2015, 04:30:34 am
content: Quote from: drdanke on May 05, 2015, 04:03:56 amNo, calibration labs effect calibration. Battery wires effect the transfer of current between the battery and the meter.effectverbto cause (something) to happen; to bring about

author: nitro2k01
author_rank: Frequent Contributor
timestamp: May 05, 2015, 05:13:51 am
content: Simply the act of replacing the wires will not affect calibration. That is not to say you couldn't do something that affects calibration while mucking about inside the multimeter if you were clumsy enough.

author: smjcuk
author_rank: Frequent Contributor
timestamp: May 05, 2015, 06:15:18 am
content: I literally just did the same thing two days ago to a megger. Will be fine.Bet it had Duracells in it.

author: electr_peter
author_rank: Unknown
timestamp: May 05, 2015, 09:49:37 am
content: Resoldering battery wires will not affect calibration in any way unless you do extremely poor job and butcher whole PCB. So do a good job and she'll be right

author: macboy
author_rank: Super Contributor
timestamp: May 05, 2015, 01:41:11 pm
content: You are much more likely to affect (not effect) the calibration by putting your greasy fingerprints all over the board while repairing the 9V battery clip. The battery clip itself will make no difference.