Dear Members,
I have an old analog voltmeter that can correctly measure DC voltage between 0v to 3v. The voltmeter is made by Toyokeiki depicted in the photos. It does not need any battery. It works using a coil and a magnet as any other analog voltmeters.
I am going to convert this voltmeter into a DC ammeter that can measure DC current between 0A to 15A.
To do this, I use a 0.2 Ohm resistor for current sensing in the circuit. Then, I use the setup depicted in the photo to measure current.
For example, if the power be 12v and the load be 8 ohms, the voltmeter shows 0.3v that indicates I = V/R = 0.3/0.2 = 1.5Amps of current.
This measurement is correct. The voltmeter measures current correctly. But It has a problem.
The voltmeter works only if I touch one pin of it by my finger. Otherwise, It shows 0v and cannot show the real voltage drop across the current sensing resistor. It seams there is some electricity that needs to get out of the voltmeter.
Please help me solve this problem so that the voltmeter can work fine without requiring to touch its pins.
Thanks
I have an old analog voltmeter that can correctly measure DC voltage between 0v to 3v. The voltmeter is made by Toyokeiki depicted in the photos. It does not need any battery. It works using a coil and a magnet as any other analog voltmeters.
I am going to convert this voltmeter into a DC ammeter that can measure DC current between 0A to 15A.
To do this, I use a 0.2 Ohm resistor for current sensing in the circuit. Then, I use the setup depicted in the photo to measure current.
For example, if the power be 12v and the load be 8 ohms, the voltmeter shows 0.3v that indicates I = V/R = 0.3/0.2 = 1.5Amps of current.
This measurement is correct. The voltmeter measures current correctly. But It has a problem.
The voltmeter works only if I touch one pin of it by my finger. Otherwise, It shows 0v and cannot show the real voltage drop across the current sensing resistor. It seams there is some electricity that needs to get out of the voltmeter.
Please help me solve this problem so that the voltmeter can work fine without requiring to touch its pins.
Thanks
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