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Old 31st Jan 2010, 12:19 pm   #123
swordholder
Rest in Peace
 
Join Date: Aug 2009
Location: East Preston, Sussex
Posts: 162
Default Re: The "Sussex" Homebrew Valve Tester.

Hello Guys
I have made a small modification to the Sussex valve tester in order to check for gas current.
No modifications are required to the PCB or power supplies.
Basically all I have done is to include a 1k resistor in series with the grid voltage supply to the top panel.
As can be seen from the attached circuit, a relay switches the anode current DVM between measuring the voltage across the 1R in the anode circuit and the voltage across the added 1K in the grid circuit.
1uA of grid current will generate 1mV across the 1k, the grid current can be read with a resolution of 0.1uA.
I have mounted the relay "dead bug style" using double sided tape to the bottom of the case.
Thanks for all the interest shown in the project.
Regards
Mike
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