ORIGINAL MESSAGE: (may be snipped)
On Thu, 10 Oct 2013 09:13:53 -0700, you wrote:
>We used to call this the 'voltmeter method' of measuring current. You put a
>resistor in
>series with a milliammeter to convert it into a voltmeter -- and then use it
>to measure
>the voltage drop across another resistor (the shunt) in series with the load.
REPLY:
No, that's not the same method. Yours works fine too, but it's different.
My method uses a current meter, not a voltmeter. The meter would be the same
range you would use without any protection, i.e. 1 amp for plate, 100 mA for
grid, etc. NOT a voltmeter.
The current meter and a low value resistor are in series. The purpose of the
resistor is to increase the total voltage drop across the meter plus
resistor to about .6 VDC, at which point the protective diode will conduct.
The value of resistor plus meter resistance should be so that the .6 VDC
figure is reached at about 110% of full scale.
73, Bill W6WRT
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