older electrometers with analog output? - Page 1
Forum section: electronics / testgear

author: coppercone2
author_rank: Super Contributor
timestamp: May 15, 2025, 03:26:53 am
content: I want a electrometer with analog output. I previously had a Keithley 616 but it seemed to utterly rage me all the time and it slowly got more and more problems until I had it, especially since all the chips are like re-badged. And I don't like the control it had, I would always end up with the wrong mode, ranging it is confusing, etc.However, I liked how you can put it in a circuit and get a DC voltage out proportional to the measurement, which can be connected to a scope.Do any of the moderner more digital keithley units have this?I am not seeing much that have resistance above 200Gohm. But I was more interested in the voltmeter function with very low bias currents and very high input impedance, so it can connect to sensitive circuits, and the ammeter function.And do any of them have less keithley-only parts that don't list commercial possibilities in their manual?

author: Kleinstein
author_rank: Super Contributor
timestamp: May 15, 2025, 07:07:55 am
content: Modern instuments tend to no longer have a service manual with schematics. The parts may be normal marked, but still hard to find. Especially the low leakage relays can be tricky to get. Another point are programmed parts like PLD, FPGA, µCs - the bare part is not enough.AFAIK the parts for the Keithley 616 are not that obscure. A few FETs may need a replacement - especially JFET types got obsolete and replaces. In part it is also selected parts - one may still find this in modern instruments, just no information on which parts are actually selected and not just stock parts.For the analog output there are 2 different versions: one is a direct analog output. However this comes without isolation and may not be what one wants from an electrometer. The other is the way via ADC, isolation and DAC. In this case one would as well look at the digital data as well. The analog out in more for things like a paper recorder and no longer that popular. So not many meters have this.

author: Brad O
author_rank: Regular Contributor
timestamp: May 15, 2025, 06:51:30 pm
content: Both of the current Keithley electrometers have analog outputs like that, the 6514 and the 6517B.They both have a 2V full-scale, 10 kΩ output for exactly like what you describe, as well as a pre-amp output for buffering and guarding.

author: coppercone2
author_rank: Super Contributor
timestamp: May 15, 2025, 08:27:41 pm
content: maYBE If i take up part time work with the bankI never saw a good deal for that. I am wondering if for some reason corporate users are HOT for electrometers. I saw this once with AC power analyzers. The guy was like in a death struggle with the percieved value of a AC power analyzer, so they were always bidding for them on ebay.Big ass factory with tons of expensive shit (like machine shop combined with costco), but for some reason they just HAD to get a deal on AC power analyzers. Maybe its because they have been getting by with a hand held DMM for 3 decades and suddenly you need a much more expensive piece of equipment that you get sticker shock? Even with your 100k budget?I was always wondering if like by some way, someone up above just steps in and denies AC power analyzer purchases. Like in particular, that one type of test equipment causes a giant stink. It sounds stupid but corporate can be mad stupid. Like they let you hit the 'snap on truck' for a crazy expensive robot pipe bender that might never be used but all hell breaks loose when you try to get AC power analyzer. I think some how it happens. I wonder if the same happens for electrometers.