# Activating a Weston Station Meter 0-300 VDC made around 1901.

Discussion in 'Power Electronics' started by janster, Jul 1, 2016.

1. ### janster Thread Starter New Member

Jul 1, 2016
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0

I have a large Weston Station Meter 0-300 VDC made around 1901. Made for a power generation plant, inside of the housing was some sort of mica wafer assembly wired in series with the +binding post. I would assume that this was some sort of resistor, but it is no longer conducting current. Applying just one volt runs the meter to 125V, 3 volts and the needle pegs. Is there an inline resistor I can choose which can be used to make this meter function at line voltage? All I have come up with so far is to use a 6vdc wall wort transformer and some resistors, but surely this was not the way that the meter was set up back when.

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
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Does the meter have any small print on the dial to indicate the current corresponding to full-scale deflection?
If not, try applying 1V via a known resistor or two and noting the scale readings, so that the sensitivity can be calculated.

3. ### janster Thread Starter New Member

Jul 1, 2016
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0
Thank you for replying. I used a 1.5v D cell and a 55ohm pot- dialing the pot down a bit, the Weston meter read approx 125v. With no pot, the meter pegs at over 300v with the D battery. I then used a 6 volt wall wart and powered by 22v ac through a powerstat. The wall wart put out about 1volt. That drove the Weston meter to about 125v.

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4. ### ian field AAC Fanatic!

Oct 27, 2012
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You're well on the may to discovering the mA/V specification so you can calculate the value of a replacement multiplier resistor.

You can get high voltage resistors that would be OK for 300V fsd, but its worth using about 3 in series to make the required resistance, to improve safety.

5. ### Alec_t AAC Fanatic!

Sep 17, 2013
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You need to know accurately how much resistance gave you that 125V reading. Use an Ohmmeter to determine that. "Dialing the pot down a bit" is a tad vague .

6. ### KeepItSimpleStupid Distinguished Member

Mar 4, 2014
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Generally that won't work.

Take a potentiometer and vary it with a voltage source that gives you 1/2 scale deflection. Measure the voltage across the POT. That should get you the ability to get the current for 1/2 scale.

Take the POT out of the circuit and measure it. That will be the meter resistance,

From there, we can figure out the required series resistance,

7. ### joeyd999 AAC Fanatic!

Jun 6, 2011
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That is an absolute work of art.

nsaspook likes this.

May 4, 2013
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