Building a Digital Ammeter...

Ok using an ADC is no problem but how do I go about measuring a current between 0 to 50amps with a 0.1A scale ?

Im sure no shunt resistors can take that kind of current so what other options are available to be able to do this ?

Thanks in advance !

High Current Measurements

If you are measuring AC then you could consider a Current Transformer - take care as the secondary winding of these things can kick out amazing voltages if open-circuited.

For DC I know of no alternative to shunts - if you have a car battery tested at a garage they will use a gizmo with a huge shunt to measure short-circuit ability. It looks like an inch-wide, two foot long strip of steel for the shunt.

Could you use a hall-effect transistor strapped onto the side of a conductor and infer amps from magnetic field?

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Hmm yea it is DC and the other trouble is not only measuring 50A but also with a resolution of like a 0.1A step size.

Im actuall measuring the current coming out of a 500W computer PSU on the 12V, and 5V lines

I mentioned in another post about Hall effect devices. You could use one of these to measure DC current, but being a non-contact device, I'm not certain about it's accuracy.

It is possible to buy Hall effect tong ammeters, which will read both AC and DC.

EDIT: Sorry mechie - I didn't see that you already mentioned it

I have used Tong type ammeters with hall-effect sensors giving accuracy of 0.01A. Cool 8)