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Re: [Amps] plate voltage meter shunt

To: "Bill Turner" <dezrat1242@yahoo.com>, "Amps" <amps@contesting.com>
Subject: Re: [Amps] plate voltage meter shunt
From: "Jim W7RY" <w7ry@centurytel.net>
Reply-to: Jim W7RY <w7ry@centurytel.net>
Date: Sat, 3 Nov 2012 22:51:14 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
As I remember... Henry (I know the Viewstar/B&W works this way) does that in some of their amps. I've had mixed results. As the bleeders heat up and the caps do too, the plate voltage meter drifts. And the voltage is not the same across each cap. The one with the metering circuit has lower voltage across it.

73
Jim W7RY


-----Original Message----- From: Bill Turner
Sent: Saturday, November 03, 2012 7:22 PM
To: Amps
Subject: Re: [Amps] plate voltage meter shunt

ORIGINAL MESSAGE:
On Sat, 3 Nov 2012 14:15:44 -0700 (PDT), W9IIX wrote:

I am installing a meter to measure plate voltage 1-5000v@ 1a dc,
the meter has a 1ma fs rating.  the serial resistance I have
made up in the past has been 3 watt metal film resistors in
series. since they can only rated for 200v per resistor it takes
many to do the job. Can some other resistor type with a
higher rating be used in a safe manner for this purpose?
...tnx, Doug,w9iix

REPLY:
Does your power supply have a string of electrolytic capacitor with equalizing resistors across each one? Install the meter in series with the bottom (negative
end) resistor and shunt it with a potentiometer or fixed resistor for
calibration. A few minutes with Ohm's law will give you the values.

Hint: do the calculations based on the full scale reading of the meter, not the
actual HV reading.

73, Bill W6WRT
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