Screwed up, got wrong panel meter, can I recover..?

Thread Starter

thedoc8

Joined Nov 28, 2012
134
I bought a panel meter to measure amps. 0 to 30 amps. Did not realize I ordered a dc amp meter when I need a ac amp meter.

Is their any easy way convert the dc to measure ac. No given much thought yet, cause Im ticked. I thought about just a full bridge on the shunt, but don't know. any ideas. Thanks
 
Measuring AC amps needs a lot of thought, unfortunately.
Is the current waveform sinusoidal? What frequency?

A DVM is usually average responding, RMS reading and only works on sine waves. It won;t correctly read certain kinds of loads.
A TRMS meter is usually more expensive and it's NOT limited to sine waves. (Fixed - basically a typo, forgot a word)
There is always a frequency limitation.

What is the load(s) that your trying to measure?
 
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crutschow

Joined Mar 14, 2008
23,742
So the DC ammeter is rated for 30A?

What is the AC voltage?

You could possibly use a full-wave bridge in series with the AC, with the shunt at the center of the bridge.
That would require 30A diodes.
Schottky type diodes would minimize the voltage drop and power dissipation, but it would still be about 30W @ 30A.
 

crutschow

Joined Mar 14, 2008
23,742
A DVM is usually average responding,
The TS wants to measure AC current, and AC panel meters normally measure the average.
A TRMS meter is usually more expensive and it;s limited to sine waves
It may be more expensive but it's not limited to sine waves.
A TRMS meter will measure true RMS for non-sinusoidal waveforms (within its crest factor limits), that's why it's called TRMS.

If you limit it to sinewaves, than the typical average responding meter, calibrated to read RMS, works fine.
 
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Thread Starter

thedoc8

Joined Nov 28, 2012
134
I bought a panel meter to measure amps. 0 to 30 amps. Did not realize I ordered a dc amp meter when I need a ac amp meter.

Is their any easy way convert the dc to measure ac. No given much thought yet, cause Im ticked. I thought about just a full bridge on the shunt, but don't know. any ideas. Thanks
Its just a 0 to 30 amp panel meter 60hz sine, it will just measure the amp draw of 4 transformers paralleled . No problem, just reorder the correct meter as I still have use for the one I ordered. Thanks
 

Thread Starter

thedoc8

Joined Nov 28, 2012
134
So the DC ammeter is rated for 30A?

What is the AC voltage?

You could possibly use a full-wave bridge in series with the AC, with the shunt at the center of the bridge.
That would require 30A diodes.
Schottky type diodes would minimize the voltage drop and power dissipation, but it would still be about 30W @ 30A.

Meter is rated 30 amps, 120 volts. I have the 75mv, 30 amp shunt that goes with the meter.
 

Thread Starter

thedoc8

Joined Nov 28, 2012
134
So the DC ammeter is rated for 30A?

What is the AC voltage?

You could possibly use a full-wave bridge in series with the AC, with the shunt at the center of the bridge.
That would require 30A diodes.
Schottky type diodes would minimize the voltage drop and power dissipation, but it would still be about 30W @ 30A.
Going down and try some of the subjections. Thanks for your time.
 

Thread Starter

thedoc8

Joined Nov 28, 2012
134
That device has a minimum input of 5mVrms which represents 2A from your 75mV-30A shunt.
A high accuracy op amp precision rectifier might be a better approach.

What's the resolution of the DC ammeter?
Just a cheepo 2.5. This is just to make sure nothing is shorted, so precision is not needed. If the meter slammed to >30 I know I have a problem.
 
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