Amp Meter Project

[DALEE]

Need a diagram for building an amp meter using a uv meter movement
in the range of 0 to 2 amps

 

[kchriste]

Why are you using a "uv meter movement" for an ammeter? Seems kind of odd to me. Can you explain why you want a quasi log ammeter?

 

[JimB]

What is a "uv meter movement" ?

JimB

 

[ericgibbs]

What is a "uv meter movement" ?

JimB

hi Jim,

I read it a couple of ways,

A ultra violet galvo movement or more likely he wants to convert microvolt meter movement from µV to a 0 to 2A ammeter.

Perhaps he will enlighten us.

hi DALEE,
If it is a µV meter to ammeter conversion we need to know the micro amps full scale deflection of the meter and the fsd voltage or coil resistance.

 

[KMoffett]

Could they have transposed the letters and meant a "VU" meter...since they respond the AC signals.

Ken

 

[JimB]

A ultra violet galvo movement or more likely he wants to convert microvolt meter movement from µV to a 0 to 2A ammeter.

Could they have transposed the letters and meant a "VU" meter...since they respond the AC signals.

Exactly, too many unknowns and assumptions.

JimB

 

[Willbe]

Need a diagram for building an amp meter using a uv meter movement
in the range of 0 to 2 amps

The meters that go across shunts are usually 50 mV, full scale.

 

[DALEE]

I'm dylexic Sorry everyone. I have a VU meter movement, from a recorder I do not have a clue as to what the internal resistance is. My ohm meter pegs the needle. If the amp meter is inserted into the circuit dosent this add resistance to the circuit?

 

[KMoffett]

Ideally, an ammeter adds no resistance to a circuit. Practically, it adds a very, very small amount.

Ken

 

[kchriste]

Probably the easiest way to figure out the sensitivity of your meter is to put a 1Ω resistor in parallel with your VU meter. Then connect a 1KΩ resistor in series with the 1Ω resistor//meter. Connect this series/parallel network across a 10Vdc (Or 9V battery) source and see what deflection you get on the meter. If you get very little deflection on the meter, disconnect the circuit and replace the 1Ω with a 10Ω. OR, if the needle pegged, then change the 1KΩ to a 10KΩ and leave the 1Ω as is. You could also use a pot also to zero in on the full scale deflection of the meter, but be careful not to burn out the pot by reducing the resistance to much. Once you have the meter reading full scale, you can either use ohms law to figure out the mV across the meter or you can measure it with your voltmeter if it has a mV scale.

 

[Willbe]

I'd just use a series high value R and any battery. Adjust the R for a full scale reading or close to a full scale reading, measure the V across the R and scale up if you have to, to figure full scale µA. I = V/R. The meter movement is a current-operated device.

If you then measure the V across the meter movement, then the meter movement resistance is V/I, with I from above. Then the movement will be fully characterized.

If you have your ohmmeter specs, you already know what current is excessive for this meter movement.

You could also use the ohmmeter as a battery, and just put the series R in series with your ohmmeter and the meter movement.

 

[DALEE]

I will try your setup thanks for the info
DALEE

 

[chemelec]

I will try your setup thanks for the info
DALEE

Most Analogue VU meters are about 200 to 250 uA full scale.
And Typically around 100 uA at the -3 Db point.

There Scale is NOT Linear, so it will not make a very good amp-meter.

 

[JimB]

Most Analogue VU meters are about 200 to 250 uA full scale.
And Typically around 100 uA at the -3 Db point.

There Scale is NOT Linear, so it will not make a very good amp-meter.

As this is probably a moving coil meter, the basic movement will be linear.
Re-drawing the scale will fix the linearity problem.

JimB

 

[chemelec]

As this is probably a moving coil meter, the basic movement will be linear.
Re-drawing the scale will fix the linearity problem.

JimB

Mine are Also Moving Coil meters. But Definately NOT Linear.

Reguardless of that, it can be used as an Amp-meter and Calibrated accordingly.

 

[JimB]

Mine are Also Moving Coil meters. But Definately NOT Linear.

OK, I am a bit surprised at that but I will defer to your greater knowledge.

Reguardless of that, it can be used as an Amp-meter and Calibrated accordingly.

And the scale will look a bit odd.

JimB