metrix: 310-D ; Lampemetre

 Hello!

I'd like to know if this tester is a mutual conductance one.

Regards

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Yes, it is. You need to change grid potential by 1 Volt and measure the plate current difference. It's a very robust product, well appreciated in France by collectors,

 Christian

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Hi Mr. Adam,

the maoeuvre you're describing is called 'grid shift method'. This cumbersome procedure requires manual interaction and calculation of transconductance. In addition, using a large delta Ug1 (you're mentioning 1 Volt) results in an average transconductance over this grid range (problem: secant vs. tangent). Also the best German tube testers (e.g. Neuberger 370/375) are restricted to this indirect method of measuring transconductance.

In contrast mutual conductance measurement is automatic. This case the grid is modulated using a small sine wave signal of either the line frequency or a considerably higher audio frequency (e.g. 1400 Hz) of constant amplitude.

Kurt  Schmid

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Thanks for the accurate answer. Because I was not sure, I prefered to describe to procedure. But it's really not complicated doing this this way,

M f G from France

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