Analog Voltmeter reading volt and amps.

[Frankli]

I have an analog voltmeter and I can read current this too.
I wonder if you can add a switch with a shunt to a voltmeter to also read current. The problem I have is to make the scale being: 10v = 1A, 2A = 20v, 1A = 30R . Any circuits ideas?

Sorry my english

Thanks!

Frankli

 

[Hayato]

The biggest problem is that the input impedance of an analog voltmeter is high, around 20k.

You'd have to modify the voltmeter and make a connection directly to the galvanometer, with a shunt.
Generally, the galvanometer brings its specs behind, for example, its resistance and deflection current.
The deflection current is the current that makes the galvanometer have full deflection. With those information, you'll be able to make the ampmeter.

 

[Willbe]

With a shunt you need to use a four terminal Kelvin connection.

 

[Roff]

I have an analog voltmeter and I can read current this too.
I wonder if you can add a switch with a shunt to a voltmeter to also read current. The problem I have is to make the scale being: 10v = 1A, 2A = 20v, 1A = 30R . Any circuits ideas?

Sorry my english

Thanks!

Frankli

With no amplification, the shunt would be 10 ohms, and the voltage drop across it at 1A would be (surprise!) 10V. The Dissipation would be 10W. At 2A, the dissipation would be 40W. It would be cheaper and easier to buy a multimeter. If this is for a power supply, it could be done with some amplification.

 

[Frankli]

Thanks for all!

Frankli