Having just bought a voltmeter/ammeter with no instructions I've written how to wire a digital voltmeter ammeter from what I tried here as it may help you.
After dabbling with a couple of synthesiser modules that I’ve been building recently, it became apparent that my self-built power supply wasn’t quite up to the job. You can read about how I built it here. If you’re in the market for a ready built unit I have an article of what bargains can be had at the moment here.
The main thing that my home built power supply was missing was meters to show me what current was being used. This is a useful indication of a fault if a newly built board takes way too much current when turned on. If you’re quick enough to turn it off you can save a fair bit of damage.
After looking around on Amazon to see what was available I found these HeroNeo® DC 100V 10A Voltmeter Ammeter Blue + Red LED Amp Dual Digital Volt Meter Gauge. There seems to be quite a few different suppliers but they all seem to be very similar. They seemed to be ideal to upgrade my power supply. If you’re interested in buying the same I’ve put some amazon links below.
When I received them I was extremely happy to find out they were the exact size as the voltage only meters I was replacing.
These were the meters that were being replaced. Just showing voltage, it was pretty easy to work out how to connect them!
They are held by plastic ridges on the side of the meter bodies which squeeze together as you push the meter in the rectangle hole then spring out holding it firmly on the front panel.
In this picture you can see the panel cut out and the plastic meter sides that hold it in place.
That was the good news. The bad news was there was absolutely no documentation or notes of any sort. A check back to the website and there was no mention of wiring them up or other links or anything at all. While the previous meters only had black and red wires, it was easy enough but these had thin black and red and thick black, red and blue. Talking about thick maybe I am by not knowing instinctively how they should be connected. If you’re like me maybe I can help you wire yours.
The meter comes with to plugs with wires that only can connect to the two sockets. Easy enough so far!
After a bit of experimenting I thought I had got it but not quite. In the end I realised that the thin black and red wires are to power the voltage and current meter. For my application I found that the blue wire was for the load but negative load and not positive as I had first thought.
As the meters were going to be fed by the power supply output I wired them as indicated below.
The new power supply output then becomes the red positive output and the blue (load) negative output. You can see this in the picture below.
As you can see I've used a terminal block to link the thick red to thin red and thin black to thick black. The power supply output board red and black connect to the meters reds and blacks and the power supply output is now the red and blue.
Now when connected up you can see the current that is being used.
The completed wiring of the voltmeter ammeter with the power supply. Here you can see the power supply set to 12V and the project that it's connected to is using 0.12 amps.
When I first tried it I thought it wasn’t reading current so be aware that it will only read down to .01 of an amp so if your circuit is only using a few milliamps the meter won’t read any current.
Considering the price I’m really happy with the meters and they certainly help me in my hobby. Hopefully this article will have shown you how to wire a digital voltmeter ammeter.