Three-Scale MA Meter

[W9ZSL]

I have an odd-ball meter which looks like a Simpson but is labeled O.B. McClintock Co., Minneapolis.  It has three scales 0-300, 0-150 and 0-15 MA.  There is nothing on the meter face that gives me any info about it.  I'd like to use it for something.  Question is, how do I determine where to start computing shunts?  Is this a 300 MA meter without shunts or is it 15 MA?

[N2DTS]

Its likely none of the above, no shunt at all, it will be micro amps.

Grid, screen and plate?
For something like a 4D32.

You make all the shunts and switch the meter to them.

[KA2DZT]

Look at the very bottom of the meter face, it may say what the full scale current is.

[W9ZSL]

Nope, all it says is Milliamperes Direct Current.  The back is actually stamped with McClintock so even though this looks like a Simpson, it technically isn't.  I tried to do research on the company but came up empty.  Resistance is 6.8 Ohms.

[KA2DZT]

Nope, all it says is Milliamperes Direct Current.  The back is actually stamped with McClintock so even though this looks like a Simpson, it technically isn't.  I tried to do research on the company but came up empty.  Resistance is 6.8 Ohms.

6.8 ohms seems about right for the 15ma scale.  Usually the meter is a 1ma movement.  1ma movements usually measure around 50-60 ohms.  So, about 6 ohms seems right for about 10ma-15ma shunting.

Try putting some small current through it with another current meter in series and find what current makes it read full scale.  Use a battery in series with some resistance to limit the current.  Use a pot, for the series resistance, to make adjustments.

[MikeKE0ZUinkcmo]

Use a power supply, with 10K resister, and a known good current meter(DVM) in series with the meter.  At full scale, answer is on the DVM, with a second DVM read the voltage across the meter.  

[W9ZSL]

I won't have a problem figuring the thing out.  I suspect it probably is 15MA.

[N8ETQ]

       I have a "Cheapie" VOM that runs off
2 X AAA Batteries. On the OHM X 1000 range
he outputs 0.6 mA, on the OHM X 100 range it
offers up 6 mA and on the ohm x 10 range provides
a meter busting 60 mA.   Pretty handy for
getting a rough Idea.

YMMV

/Dan

[W9ZSL]

Got plenty of meters to check it out.  I'm just not sure what I can use it for.

[WBear2GCR]

look through the glass toward the bottom of the meter, the area left or right above the adjuster, it may say "F.S. = xx ma.

you can use it for measuring current?

Guess you need to build a small homebrew transmitter/exciter to match the meter??

[W9ZSL]

I was actually thinking of using it in a 4-65A modulator.