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Old 17th April 2016, 01:55 PM   #1
Ron E is offline Ron E  United States
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Default Old Weston Voltmeter

I have an old Weston Voltmeter, a model 341. I am guessing the date around 1940 or so. I bought it (~$10) mainly because it looks neat, maybe to put on a curio shelf or into some sort of mad scientist display.
High Frequency Voltmeter up to 30 volts Equipment Weston Ele

Mine has 2 ranges, 7.5 and 15V and is incomplete: the top, clasp, handle and hinges have been removed as it was probably built into a display or instrument or something where those were not needed.

It seems to function, but reads the wrong voltage. I opened up the back and there seem to be hand wound wirewound resistors on cards inside. I have read that these can go bad.
http://www.richardsradios.co.uk/west...0341meter.html
Is any inaccuracy likely to be in these rather than in the galvanometer itself? Do the movement's magnets discharge over time at all?

Edit: I am not looking for knee-jerk posts by people who know nothing about these meters, which were some of the best that could be bought back then. I am curious to know mainly if the galvanometer is likely to be a source of the issue before tearing into it further.
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Last edited by Ron E; 17th April 2016 at 07:40 PM.
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Old 17th April 2016, 02:02 PM   #2
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Wirewound resistors do not 'go bad'. If discoloured they may have got hot but that is about it.
Sounds like a test meter for the Automotive Electrician. 6V and 12V battery testing. Circa 1950.
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Old 17th April 2016, 07:33 PM   #3
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Quote:
Originally Posted by Ron E View Post
I have an old Weston Voltmeter, a model 341. I am guessing the date around 1940 or so. I bought it (~$10) mainly because it looks neat, maybe to put on a curio shelf or into some sort of mad scientist display.
High Frequency Voltmeter up to 30 volts Equipment Weston Ele

Mine has 2 ranges, 7.5 and 15V and is incomplete: the top, clasp, handle and hinges have been removed as it was probably built into a display or instrument or something where those were not needed.

It seems to function, but reads the wrong voltage. I opened up the back and there seem to be hand wound wirewound resistors on cards inside. I have read that these can go bad. Is any inaccuracy likely to be in these rather than in the galvanometer itself? Do the movement's magnets discharge over time at all?
I have several dozen Weston meters dating back to 1898 (scale hand drawn with quill pen) the good ones still read within 1% even though they were last calibrated 60yr. ago. Aging of components is extremely unlikely. The power meters and electrostatic voltmeters are magnificent pieces of engineering worthy of displaying in a clear case even though you lose the antique value. When I unpack I could send a scan of their catalog describing how they all work.
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Old 17th April 2016, 07:56 PM   #4
Ron E is offline Ron E  United States
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Thanks Scott! I added a link to where I found that the resistors can have issues. Mine is an AC/DC meter.
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Old 17th April 2016, 10:15 PM   #5
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Originally Posted by Ron E View Post
Thanks Scott! I added a link to where I found that the resistors can have issues. Mine is an AC/DC meter.
I see, my meters were all kept at the Tufts U. lab so no mold or poor storage.
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