can i use led voltmeter as ammeter

[4tuty]

**broken link removed**

**broken link removed**

i have both led voltmeter. can i use this voltmeter as ammeter by connecting in series?.:sad: it's not working when i connected

 

[d123]

Hi,

Voltmeter as ammeter uses a shunt resistor to sense the current and measure the voltage drop across the resistor, as in a difference amplifier, if that's what you mean by "in series", 4-wire sensing.

If the second has an independent power supply (not powered by same red and black cables in photo for measuring), then you should/could be able to use a shunt resistor to measure current, you need to find datasheet information about the device inner workings and to know the possible input range, and calculate an appropriate value shunt resistor based on this information.

I don't know, but suspect that as the first uses the Black cable as voltmeter power supply negative/return and as the measurement negative, it might not be possible to place the leads at either end of a shunt resistor, but don't take my word for it. Again, you need to find datasheet information about the device inner workings and to know the possible input range.

Without knowing more about how those voltmeters are made, it's hard to say.

 

[ahmed saad]

you can insert resistor ( low value ) in series and measure voltage across it then calculate I = V / R
R should be very small to be neglected in total circuit resistance calculation

 

[kpc]

ahmed saad is right. especially stone resistors are useful for this purpose, they provide low resistance & high maximum power rate.

 

[chuckey]

No neither voltmeters shown is suitable to measure current. The standard for current measuring is a 100mV (.1V) voltmeter. So you insert a low value resistor in the line in which you want to measure current. This resistor you arrange to drop the required .1V at the measurement current. So suppose you have a current which you think is about 4A. 10 A would be a good range to measure this on, so you would use a resistor of .1/10 = .01 ohms and the meter would display 4.00.
With these electronic meters, it is better if the meter supply is completely isolated from the actual measuring circuit and does not use a wire that is common to both.
Frank