10A panel current meter notes (PID: 574)

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jbeale
 
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Joined: Sat Nov 13, 2010 3:34 am

10A panel current meter notes (PID: 574)

Post by jbeale »

Just in case anyone's curious, I got two of the 9.99 A panel current meters today.
https://www.adafruit.com/products/574

It has separate leads for +5V power and the current sense, but they are not isolated. The two negative leads are connected internally, for a common ground. With the 9.99 A display format, the resolution is 10 mA. There is a "scale" trim pot available on the back, but no "offset" trim. With a 0.500 A current applied (per Fluke 179) the available trim adjustment range gave an indication from 0.41 A to 0.50 A (unit 1) and 0.39 to 0.45 (unit 2).

The burden voltage at 0.5 A is 22 mV if you use the provided connector and pigtail, but most of that is just the external wires and connector; the built-in shunt is about 10 milliohms (5 mV at 0.5 A).

At the low end, the meter reading goes from an indication of 0.00 to 0.01 at 36 mA input, and from 0.01 to 0.00 at 34 mA. The meter itself draws 20 mA from a 5V supply.

Internally, the device has the LED display PCB stacked behind a current sense PCB. The latter has two SO-8 packages (op amp, regulator?) with the tops sanded to prevent identification. By scratching some foil on the PCB on the current sense path, I was able to bring unit 2 up to an indication of 0.50 with my 0.500 A test current.

The meter will work OK for my intended purpose, but if Adafruit should choose to stock a panel meter with a lower range (1 A or 2 A) I would be interested.

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john444
 
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Joined: Sun Mar 04, 2012 2:42 pm

Re: 10A panel current meter notes (PID: 574)

Post by john444 »

JBeale,

I came across your post only today.
I successfully modified the 10A panel meter for 1A without much problem.
Swapped out the .01-ohm shunt for a 0.1-ohm 4-terminal resistor.
Worked well for me.

No simple way to reduce the burden voltage though.
That is just the consequence of having a basic 100-mV meter.
If you really need a lower burden voltage,
you could add an op-amp in place of the shunt resistor.

IMHO they are a BANNED at the price.
Check out my other post "Modifying the panel mount V & A meters " from March 04, 2012.

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