# Digital Panel Meter Interface

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#### mark43

##### New Member
I am building a power supply (16v 6.6a) and would like to monitor amperage output
I have tried using resistance wire on the ground side (return to supply),
Measuring voltage drop across it. This works but I don't think this is the best way to do it.
So I got a current sensing shunt resistor (.1ohm 5watt) its good for 15A
I like this but, my amperage reading on the digital meter is off by.05A
how do I adjust the circuit to compansate for the error. Or do I need a different value shunt resistor.

Mark

#### Sebi

##### Active Member
What is the panel meter sensitivity? 200mV?

#### mark43

##### New Member
It is configurable for 200mv, 2v, 20v, 200v, 500v ac or dc and also
milliamps - 200ma
I have it set for 2v, this gives me the range I need, ie allows me to read over 2.0a
The panel meter is a pm128e from circuit specialists

https://www.web-tronics.com/panelmeter.html

Mark

#### Chippie

##### Member
The value of your series resistor can be calculated from :

the fsd of your meter, currently set to 2v

the max load current, e.g 6 amps.

from Ohms law we get R=V/I so,

2/6 =0.33333 Ohms and the power rating from V*I or
2*6 = 12 watts.......

Get the drift ?

BTW there's nothing wrong with using a series resistor in the neg or pos line, but try and make it as low as poss to minimise volt drop and dissipation

#### mark43

##### New Member
Sorry but I am confused.
The shunt resistor that I am using is good for 15A

https://www.precisionresistor.com/PLV5.htm
it is a 5w .1a 1%, Current sensing shunt resistor

My actual amp reading is off by .05a. I would like to adjust it so it is correct.
I am unsure on how to do this. This is my question.
I am a newbie to electonics, self learning,
It is easy to talk over my head.
Any ideas on how to adjust the circuit.??.
Do I need a .01a shunt resistor

Mark

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#### Sebi

##### Active Member
Configure the pnelmeter to 200mV, and apply 0.01 ohm shunt resistor. If the panelmeter is 3,5digit (unfortunately the link is dead), the max. readout is 19.99A.

#### mark43

##### New Member
Sebi,
So I got the wrong shunt resistor, I will try one that is .01a.
I have to order it, when I get it I will post the results.

Is there any way to adjust the exsisting circuit so it reads correct, Still using the .1a shunt resistor.

The links work I just cked them

Thanks Sebi.

Mark

#### Sebi

##### Active Member
Yes, in 200mV range You can calibrate it with other multimeter.

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