Checking Western Electric panel meter - UK Vintage Radio Repair and Restoration Discussion Forum

pcravero · 17th May 2017, 8:40 am

Hello.
Last weekend in Marzaglia flea market (Italy, near Modena, twice a year, worth a visit IMO) I bought a 200Vdc Western Electric meter. It misses the shunt resistor and turns out to be almost 1mA fs. I want to use it on a bench supply (to be).

"Real" problems of this new toy are: the glass moves back and forth and it is dirty.

As visible on the second picture the glass is free to move, maybe 1mm. It sits on an L-shaped metallic ring that keeps it in place when the movement is removed. Being my first instrument of this kind I wonder if it supposed to be that way? Or some o-ring went missing? How about the adjust screw in the centre: should it rotate the whole glass or move on its own?

I assume that glass and case can be cleaned with a wet cloth and non-aggressive soap.

Last question: what happens if I don't mount it on a steel plate? I need a different shunt resistor, maybe adjustable, but will readings be equally reliable?

Thanks for reading, and helping.
Paolo

Ed_Dinning · 17th May 2017, 8:52 am

Hi Paolo, it should make a good indicator for a power supply.
It can usually be dismantled by removing the small screws at the rear side of the case and gently pulling the front of the case forwards.
You should then be able to give it a good clean.
Given the centre zero setting screw it will probably be better to glue the glass back in, a sort of "black Bostic" would have been the original adhesive. There may also have been a metal ring in there holding the glass in place.

If not mounted on a steel plate the calibration may be slightly out, but no proble as you will be fitting a new series multiplier resistor for the range you need. Typical value of this resistor will be 1Kohm for each volt of full scale deflection.

On re-assembly turn the adjusting screw so the small peg that engages the meter movement aligns with the slot in the adjusting arm and bring the case together carefully.

Ed

pcravero · 17th May 2017, 10:33 am

Hello Ed,
thank you for your prompt answer. It was easy indeed to open it up and separate the front of the case from the movement block.

The metal ring is present, glued or stuck I don't know, so the glass cannot be removed. I will try to unlock the zero setting screw.

Too bad I did not look for a companion (milli)ammeter for the PSU! Well, that's another reason to visit upcoming rallies!

Paolo

Ed_Dinning · 17th May 2017, 9:18 pm

Hi Paolo, they were a fairly common design of meter so you may find more of them about. If not you can always see what the forum members have in their junk boxes.
As it is basically a 1mA meter it is easily adaptable with an external shunt to read higher current.
I believe there was also a discussion on the forum about re-scaling meters and the software available to do it.

Ed

17th May 2017, 8:40 am	#1
pcravero Triode Join Date: Aug 2009 Location: Torino, Italy Posts: 47	Checking Western Electric panel meter Hello. Last weekend in Marzaglia flea market (Italy, near Modena, twice a year, worth a visit IMO) I bought a 200Vdc Western Electric meter. It misses the shunt resistor and turns out to be almost 1mA fs. I want to use it on a bench supply (to be). "Real" problems of this new toy are: the glass moves back and forth and it is dirty. As visible on the second picture the glass is free to move, maybe 1mm. It sits on an L-shaped metallic ring that keeps it in place when the movement is removed. Being my first instrument of this kind I wonder if it supposed to be that way? Or some o-ring went missing? How about the adjust screw in the centre: should it rotate the whole glass or move on its own? I assume that glass and case can be cleaned with a wet cloth and non-aggressive soap. Last question: what happens if I don't mount it on a steel plate? I need a different shunt resistor, maybe adjustable, but will readings be equally reliable? Thanks for reading, and helping. Paolo Attached Thumbnails

17th May 2017, 8:52 am	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Checking Western Electric panel meter Hi Paolo, it should make a good indicator for a power supply. It can usually be dismantled by removing the small screws at the rear side of the case and gently pulling the front of the case forwards. You should then be able to give it a good clean. Given the centre zero setting screw it will probably be better to glue the glass back in, a sort of "black Bostic" would have been the original adhesive. There may also have been a metal ring in there holding the glass in place. If not mounted on a steel plate the calibration may be slightly out, but no proble as you will be fitting a new series multiplier resistor for the range you need. Typical value of this resistor will be 1Kohm for each volt of full scale deflection. On re-assembly turn the adjusting screw so the small peg that engages the meter movement aligns with the slot in the adjusting arm and bring the case together carefully. Ed

17th May 2017, 10:33 am	#3
pcravero Triode Join Date: Aug 2009 Location: Torino, Italy Posts: 47	Re: Checking Western Electric panel meter Hello Ed, thank you for your prompt answer. It was easy indeed to open it up and separate the front of the case from the movement block. The metal ring is present, glued or stuck I don't know, so the glass cannot be removed. I will try to unlock the zero setting screw. Too bad I did not look for a companion (milli)ammeter for the PSU! Well, that's another reason to visit upcoming rallies! Paolo

17th May 2017, 9:18 pm	#4
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Checking Western Electric panel meter Hi Paolo, they were a fairly common design of meter so you may find more of them about. If not you can always see what the forum members have in their junk boxes. As it is basically a 1mA meter it is easily adaptable with an external shunt to read higher current. I believe there was also a discussion on the forum about re-scaling meters and the software available to do it. Ed