Author Topic: Keithley 181 - Nanovoltmeter  (Read 7253 times)

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Offline Kosmic

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Re: Keithley 181 - Nanovoltmeter
« Reply #50 on: December 04, 2019, 04:45:54 pm »
BTW if the volt ranges are flaky it's probably the 2 big relays being a little bit dirty. Normally I clean them with some deoxit and a piece of paper.

I fixed 3 x Keithley 181 and they all had that problem.
 

Offline HighVoltage

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Re: Keithley 181 - Nanovoltmeter
« Reply #51 on: December 04, 2019, 05:28:33 pm »
BTW if the volt ranges are flaky it's probably the 2 big relays being a little bit dirty. Normally I clean them with some deoxit and a piece of paper.

I fixed 3 x Keithley 181 and they all had that problem.
Thanks for this info.
So far my 181 performs very well in the V and mV rage.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline HighVoltage

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Re: Keithley 181 - Nanovoltmeter
« Reply #52 on: December 29, 2019, 01:01:50 pm »
For Christmas I got one more Keithley 181 from a friend .... he gave up on the repair.

Broken and taken apart, all in one big cardboard box.
Many plastic parts are broken.
Allegedly showed garbage on the display.

I am looking forward to this repair.


« Last Edit: December 29, 2019, 01:05:08 pm by HighVoltage »
There are 3 kinds of people in this world, those who can count and those who can not.
 

Online guenthert

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Re: Keithley 181 - Nanovoltmeter
« Reply #53 on: June 18, 2020, 07:40:01 pm »
[..]
I've put a short directly at the screw terminals of the nanovolt preamp input under the shielding
[..]
  I didn't think of that.  Thanks for the hint.  With that short in place, readings in the most sensitive range (2mV at 6.5 digit, i.e. 1nV, resolution) with default filtering (filter 1 on, filter 2 off, damping off, are the defaults I believe) I get some 20nVpp.  This is within spec as I read it and good enough for my purpose.  Earlier, with a short using a simple copper cable on the external input, I saw noise in excess of 140nVpp, but that seems to have been largely varying thermal EMF.  Now I do need to get a proper connector ...

1004557-0
« Last Edit: June 18, 2020, 07:42:28 pm by guenthert »
 


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