Power Supply voltmeter

Bob Jeffery

New Member
I found a old analog voltmeter that has a negative and positive hookup. That's it. Would it be possible to hook this up to a PSU?
 

ganzey

banned
you could do that, just hook onto an empty molex connector. only problem is that if it is a multi rail psu the readings will be for only one of the rails. but im not sure if this would give the readings you would want.
 

Bob Jeffery

New Member
I just think it would be cool to have it hooked up, plus I would know if it was giving everything enough power.
 

The_Other_One

VIP Member
What you really need is to find some kind of wattage meter... The old Coolermaster PSU I had was quite neat with it's little wattage meter. You could watch the PSU work harder as the machine was stressed out ;)
 

Bob Jeffery

New Member
If I hooked it up to an empty molex connector, would that not like, short circuit it? I'll try hooking it up on a old psu that I have since it has a short circuit protection thing, plus I don't use it for anything.
 

Okedokey

Well-Known Member
:D If you think that would short circuit it Bob, i would politely suggest you have only the faintest idea off what to do. ;) I would therefore recommend you don't go 'hooking" anything to a PSU unless you are very careful.

The voltmeter will work fine using a Molex connector as long as you connect the colours correctly. The Molex connectors can only go one way together so the pin out is useful.

That means if you connect the volt meter red wireto the molex connector's yellow wire. Then connect the volt meter's black wire to the molex connector's Black wire. Instead you could connect the volt meter's red wire to the molex red wire to make it show 5V rather than 12V, although 12V is much more useful to monitor (its the important PSU rail).

Connect it and solder the connections, else crimps, else electrical tape.

Pin # Color Function
1 Yellow +12 V
2 Black Ground
3 Black Ground
4 Red +5 V

Then you will see a meter pointing at 12V (of 5V) all the time (hopefully).

I like the idea of the ammeter. You could salvage the face, hand and look off the old meter but install inside the voltmeter 'case' the ammeter (amps). This amp meter (ammeter) will show you current draw which would really show how much juice you are pulling much more dynamically. The ammeter you can buy easily such as here: http://www.12volt.com.au/General Htmls/webcat2003/meters.html#dcammeter but they aren't cheap.
 
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Bob Jeffery

New Member
I feel stupid :eek: I'm not as stupid as I seem, I just didn't know how voltmeters worked. I didn't know if that has to be hooked to a circuit with a load already on it, or it they could be hooked up to their own load. I have an old ammeter from a car that reads from 0-60 amps, I could just hook it up the same as the voltmeter right? I hooked up the voltmeter, it worked great! I was thinking a ammeter had to be hooked up to a circuit with a load already on it, but idk how power supplies work compared to something like a battery as far as reading the amperage. EDIT- I looked it up, and it said ammeters have low resistance. So if I hooked it up like the PSU I'm guessing that would suck every bit of power it will pull through the low resistance ammeter, possibly blowing a fuse? I don't see how you could hook up an ammeter to a PSU, seeing that if you had to connect it to a circuit, it would only see the amps drawn by whatever circuit it is connected too. Feel free to totally correct me.
 
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