ebay Digital Voltmeter strange values

[jan18101997]

I am trying to use a Digital Voltmeter from ebay to measure the the voltage and the current usage from a batterie.

strange values: it is showing me about about 10A if i just use about 5A
I am connecting it like this (Attatchment)
ebay item: http://www.ebay.de/itm/221799389984

my question is how can i get this to work?

[Twoflower]

There are several possible issues.

Have you tried to use a separate power source for the supply? It could be possible that this meter need an insulated power supply.
The *bay description indicates two ranges (50A and 100A) is there anything to configure? Like a jumper for example.

[jan18101997]

If i use an external source everything works. you have to order them in the range you need it range (0-50)

[Twoflower]

So if you're using an independent supply the displayed range is correct? The problem is that the potential of the supply GND is not the same of the main battery.

That probably means there might be no simple solution. The only idea I have is to use a switching regulator for the power supply which insulates the input from the output (not all do the trick). The only ones I found during a quick search require a 12V input with +/-10% accuracy (e.g. SIM1-1212).

[jan18101997]

Constant 12 V will not be this easy but still thanks i will give it a try.
Or temporally i just use a 9v battery.

[Brumby]

I've seen some variations of this module that are claimed to work off a common supply for the module and load.

One of those shows the negative of the module supply disconnected altogether.  Presumably it gets negative power for the module through the current sense circuitry.

No guarantees obviously, but it might be worth a try.

[stj]

you should have got one that uses an inductive loop,
that would be one less problem.

[StillTrying]

you should have got one that uses an inductive loop,

They're not very good at DC.