DC digital ammeter

[frankwas]

Hi All!

Just wanna say thank you to all that have helped me on the other project for the power supply for the amp. This is actually a supplemetry post for that amp psu.

I was wondering if anyone has some ideas how I can build a 0 - 60A dc digital ammeter because I want to find out exactly how mush juice my car amp pulls at full power and then permenantly use the ammeter for a nice effect. Can anyone please help point me in the right direction, because I am lost when it comes to ammeters. All I know is that they need to be connected in series and you get something like a shunt but I have no idea how and where to use it.

I have built this kit http://kitsrus.com/pdf/k61.pdf and used it perfectly for a digital voltmeter, but is there a way that I can convert it to the desired ammeter?

I found this kit: http://kitsrus.com/pdf/k34.pdf. On page 3 they explain how to convert the kit to display amps. However, I have worked out on a 200mV reference, I would need a 0.003ohm resistor! And the other way around if I use a 1ohm resistor then I would need a 60V reference! Can anyone please help?

Thanks.

[audioguru]

Hi Francois,
The pcb for your meter kit already has a space for a current shunt resistor. But the space is for only a 5W resistor and you need it to dissipate 3.6W or 36W to measure 60A.
You also need very heavy wires connected to the resistor.

2V/200A= a shunt resistance of only 0.01 ohms. Then 60A will read 0.6V. The resistor will dissipate 36W. This resistor will reduce the supply voltage by 0.6V at 60A.

Or you could use a 0.001 ohm resistor instead and it will dissipate only 3.6W. Then the meter will read 0.06V for 60A. This resistance will reduce the supply voltage by 0.06V at 60A.

You might be able to buy a shunt resistor as an accessory to a meter, or make it yourself with heater wire.