Install ampmeter in psu?

[D2666]

Hi, I'm new here.
Got a question about how to install an Ampmeter in a PSU.
Should it be installed on GND?

Thanks in advance

[Audioguru]

If the psu has a regulated voltage then simply tacking a current meter to the output ruins the voltage regulation.
The current meter should be designed into the circuit of the psu so that it is inside the negative feedback loop. Then its current sensing resistance has no effect on the voltage regulation.

[D2666]

It has no voltage regulator, I am in progress of building it.

[michaeliv]

What is your schematic / idea ? Are you making a variable power supply out of prebuilt modules ?
Generally you would put the ammeter on the positive side.

[mariush]

You have at least two choices.

You can use a small resistor (current shunt) to measure the voltage drop across it and optionally amplify this value to be within a specific range (0..5v for example). In this case, you would need to use a third voltage sense wire after this current shunt and constantly read the voltage there and adjust so that the output voltage will be as desired.  The more current used by devices, the higher the voltage drop on the resistor so the output will be lower, so your regulator will actually have to output slightly higher voltage.

If super accuracy is not that important, you can use one of those hall effect chips, which measure the current without a resistor (there is some resistance but it's somewhat constant at 0.01 ohm or something like that so negligible ) ... for example see ACS712 : http://www.digikey.com/product-detail/en/ACS712ELCTR-05B-T/620-1189-1-ND/1284606
They'll output a  particular amount of voltage depending on how much current flows through the wire, without affecting the voltage on the wire so you could read the output voltage of this chip and use a small microcontroller or something to convert that output voltage to Amps (with a microcontroller you could also "calibrate" each chip and correct the readings in your microcontroller to get a higher accuracy).

[D2666]

Sorry for the late reply.
I am makeing my benchPSU from a topgrade pc PSU.

Thanks for the answer.

I bought 2x of http://www.ebay.co.uk/itm/DC100V-10A-Voltmeter-Ammeter-Blue-Red-LED-Amp-Dual-Digital-Volt-Meter-Gauge-FT-/321752233227?hash=item4ae9ed750b:g:vPUAAOSweW5VUKP1

As it is my first PSU build, I'm not gonna do too much, but I've made it so it's easy to add other stuff to it.
 
Anyway, I'm starting out simple, will make my own from bottom at some point in the future, just want more knowledge, and this is more so I have a benchPSU.

Thanks