Fluke 8800A - quick question about fault - Page 1
Forum section: electronics / testgear

author: qu1j0t3
author_rank: Regular Contributor
timestamp: August 08, 2017, 10:18:31 pm
content: Noob here, just bought a nice clean Fluke 8800A from ebay… Just powered this one up and before I even get to making a reading, there seems to be an issue. On DC 20V range, the display starts at -0.0000 but immediately starts counting in the negative direction without stopping, about .005V per second. Does this problem sound familiar to anyone?I'm getting hold of the schematics. Haven't popped it open yet. Thanks for any clues.

author: bitseeker
author_rank: Super Contributor
timestamp: August 08, 2017, 10:34:41 pm
content: Welcome to the forum!Edit: See edavid's and bd139's posts, below.

author: edavid
author_rank: Super Contributor
timestamp: August 08, 2017, 10:38:45 pm
content: It's not a fault, it's totally normal for a high impedance voltmeter.

author: bd139
author_rank: Super Contributor
timestamp: August 08, 2017, 11:01:12 pm
content: For ref, 8800A on 20v range is quoted as >1000M impedance. Only on 200v and above it will probably not drift as that's 10M. As edavid says - normalAlso, nice meters!

author: bitseeker
author_rank: Super Contributor
timestamp: August 08, 2017, 11:23:32 pm
content: Interesting. On other high-impedance meters I get the values dancing around (noise), rather than building up (or down, as the case may be).

author: bd139
author_rank: Super Contributor
timestamp: August 08, 2017, 11:33:41 pm
content: My 8600A just climbs and climbs. It's probably picking up the stress electrons coming off me.

author: bitseeker
author_rank: Super Contributor
timestamp: August 09, 2017, 12:12:04 am
content: LOL, I guess seeing it climb adds to your stress. Positive feedback!

author: qu1j0t3
author_rank: Regular Contributor
timestamp: August 09, 2017, 12:54:22 am
content: OK, glad I flagged myself as noob, then.Thanks for the excellent and very fast replies, everyone.

author: bitseeker
author_rank: Super Contributor
timestamp: August 09, 2017, 02:11:38 am
content: No worries. There's so much to learn, we're all noobs at something or many things. That's what the forum is for, sharing knowledge.

author: switcher
author_rank: Regular Contributor
timestamp: August 09, 2017, 06:37:22 pm
content: These are excellent excellent excellent meters. I like mine so much, I bought another one...

author: bitseeker
author_rank: Super Contributor
timestamp: August 09, 2017, 07:21:24 pm
content: OK, I figured out why I didn't see this behavior on a regular basis. By default, the input impedance on my Keithley and HP meters are high, but not in the >1 or >10 GOhm range. Changing them (either via menus or manually ranging) then yields the constantly drifting value with no input.My Fluke 8100A is too old. Its impedance is fixed at 10 MOhm on all ranges.

author: qu1j0t3
author_rank: Regular Contributor
timestamp: August 09, 2017, 08:50:33 pm
content: I am missing a couple of the input shorting bars, though, if anyone knows a source.

author: alm
author_rank: Super Contributor
timestamp: August 09, 2017, 09:11:24 pm
content: Try Pomona 4115. They are fairly expensive (approximately $3/ea).

author: qu1j0t3
author_rank: Regular Contributor
timestamp: August 09, 2017, 09:16:53 pm
content: Thanks @alm That looks like the ticket...https://www.digikey.ca/product-detail/en/pomona-electronics/4115/501-1505-ND/736747

author: switcher
author_rank: Regular Contributor
timestamp: August 09, 2017, 10:18:42 pm
content: I think the earlier ones are nicer, the keys are more 'square' Later ones have more 'pointy' keys.

author: bitseeker
author_rank: Super Contributor
timestamp: August 10, 2017, 01:14:55 am
content: Yeah, they have their pros and cons. That's why you can't have just one (or two, or three, or ...)

author: bd139
author_rank: Super Contributor
timestamp: August 10, 2017, 08:47:15 am
content: N+1 is the magic number

author: qu1j0t3
author_rank: Regular Contributor
timestamp: August 10, 2017, 01:26:23 pm
content: Reading other Fluke threads, it seems like electrolytic cap replacement is often recommended. Is this something I should do right away on this meter?(I've done a fair bit of cap replacement on other supplies and inverters.)

author: bd139
author_rank: Super Contributor
timestamp: August 10, 2017, 01:30:05 pm
content: Might be an idea. A couple of mine have had leaky ones in and they make a mess of the board.

author: qu1j0t3
author_rank: Regular Contributor
timestamp: August 19, 2017, 07:41:00 pm
content: I opened it up, caps are clean as a whistle…