Have you guys ever tried this?
I did and everything seems to work properly except when I try to read VDC, for some reason I always get a floating value between 0 and 1V, tried with different batteries (1.5/3/9V), the output of another power supply (12V), it's always the same.
Is there any logic explanation for this behavior?
You will have to provide more information than "I did....." we don't have any clue what you did so we can't suggest why you have an issue.
If the title means what it says , then got a good idea anyway as you might get issues with common connections.
Splash out in a battery .
If you’ve made a multimeter from an Arduino , different issue - key is to let us know
hammy:
If you’ve made a multimeter from an Arduino , different issue - key is to let us know
Sorry if I wasn't clear enough.
It's just a regular multimeter, a cheap chinese one, but did the same with more expensive one and had the same issue, actually I did it for the first time with this one when the batteries leaked acid and destroyed the terminals.
What I'm doing is just to solder the power supply output cables to the battery connector, obviously I'm using the same voltage batteries would provide.
I cannot quite get why an external supply would help here.
One advantage of batteries is that electrically they are very quiet and dont introduce nosie from potential ground loops etc.
srnet:
I cannot quite get why an external supply would help here.
I always forget to turn the multimeters off.
I bought one with auto power off but:
the batteries leaked acid and destroyed the terminals
srnet:
One advantage of batteries is that electrically they are very quiet and dont introduce nosie from potential ground loops etc.
So, do you think this is the cause of the problem I'm having?
And why it does affect only VDC readings?
Most handheld battery operated DMMs use a virtual ground. That is to say if you measure between your meter Common Input pin and your battery Neg pin they are not directly connected. On most DMMs the common is Vbattery - about 6.2 volts. So reading a 9 volt internal battery normally reads about 2.8 volts.
Using your external supply What is your supply ground common to?
Ron
with this one when the batteries leaked acid and destroyed the terminals.
I'd guess something else was damaged too.
Realistically, it's time for a new meter.
I tried with different batteries (1.5/3/9V), the output of another power supply (12V), it's always the same.
Of course, the battery or power supply voltage should match the original battery voltage.
If you use a power supply it should be isolated from ground (most are).
You can buy AC powered bench top multimeters but they are more expensive.
...When I was a kid I had a [u]9V "battery eliminator"[/u] that I used for a portable transistor radio. I made a little notch in the battery cover for the wires. I did get a "buzz" (power supply noise).
Multimeters are supposed to be fully isolated, otherwise they can't measure voltages between arbitrary points
in a circuit.
You shouldn't be trying to power a meter from the mains unless its expressly designed for this with a fully
isolated supply. The circuitry inside the meter is directly connected to the probes and will be an dangerous
potentials if you are probing high voltages.
Does your multimeter have a fuse? Try this: short your probes together and let us know what the reading is. If all else fails it could be time to get a new meter. The AC power source may be too noisy and depending on how it's designed it's not transformer isolated.
DC voltage readings have a different path than the other readings. It could be there's a short inside or damage to that portion of the circuit, bad component... etc. list goes on. Hard to guess at something I can't see or test.