[Amps] meter behavior
dfmich at comcast.net
Wed Nov 13 14:37:59 EST 2013
I have several power amplifiers for the 50 through 432 MHz bands which
employ pairs of 4CX250 or similar tubes. The screens of the two tubes in
whichever amp is operational are metered separately. One has a 50-0-50
mA meter and the other has a 500-0-500 microamp meter shunted to read
steady state current like the 50-0-50 mA meter. In operation, the native
50-0-50 meter flails all over the place while the shunted meter moves at
a much more sedate pace (it's damped). I have always figured this is
because of the damping effect of the shunt on the latter meter.
So this may be one possibility for the behavior you are seeing
On 11/13/2013 6:51 AM, Steve Flood wrote:
> I am trying to select some panel meters for the next amp project. I have
> many older types to choose from in my existing stash.
> I have noticed over the years that there are meters whose needles swing
> back and forth wildly while metering grid and plate currents, while others
> seem to have a dampened movement (such as the plastic Ameritron meters)
> where the needle moves more slowly.
> Is this due to the type of meter movement (such as d'arsonal, iron vane,
> taut band, etc.), or due to the meter sensitivity (low resistance vs high
> I'd prefer meters with dampened needle movement, but all of my nice old
> Triplett, Weston, GE, Westinghouse, Simpson, Marion meters seem to be the
> non-dampened movement and very low resistance, and I'd rather not put
> cheapy-looking plastic meters on this project if possible.
> Steve KK7UV
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> Amps at contesting.com
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