That is a "chopper" basically a high speed relay mechanically tuned to operate with mimimum contact bounce, normally at a specfic frequency. They were replaced by neons and resistive photo cells, FETs and then IC's Google "chopper Amplifier" Robert G8RPI
________________________________ From: Joseph Gray <[email protected]> To: Discussion of precise voltage measurement <[email protected]> Sent: Friday, 9 August 2013, 4:44 Subject: [volt-nuts] Cool looking old stuff I'm helping the local surplus guy by going through some old gear and checking it over. Sometimes I find something useful :-) I just took apart a Millivac Instruments MV-37B DC Differential Voltmeter, mostly because I was curious to see what was inside (I haven't powered it on yet). Most of what I saw was not very impressive, but one item stood out. Take a look at the two pictures. https://dl.dropboxusercontent.com/u/19599147/Millivac%20-%20Rear.jpg https://dl.dropboxusercontent.com/u/19599147/Millivac%20-%20Closeup.jpg Joe Gray W5JG _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
