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Small, Cheap AC Panel meters - Review and teardown

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intabits:
I did a quick and dirty review and teardown of these cheap digital AC panel meters that read voltage and current.

I got a blue one and a green one:-




The insides (I can't see any markings on the main chip):-



Pros:-
Bright clear display
Cheap (abut US$3.60)
Easy to mount
Can sense up to 100A (and up to 500V)

Cons:-
Doesn't show currents less than about 750mA
Current readings seem to be be low/inaccurate
Voltage readings are also a little hit and miss, only accurate to within about 2-3%.

For low currents they are probably pretty useless, but if the load is always over 1 amp, they may have a place.

I'm thinking that it may be possible to add a trimpot to  calibrate the current measurement. (But I need to get something to accurately compare it against)

Video:-

magic:
Is this for mains?
How much overvoltage before  :-BROKE

;D

intabits:
Yes, it is for mains.
The box says: 50V to 500V, and 0-100A
(meter seems to need a minimum of about 20V to operate)

SiliconWizard:
How is the current sensing achieved?

intabits:
The unit comes with a current transformer, that connects via a 2 pin inline connector to a flying lead coming out of the back of the device.
The mains is connected via 2 screw terminals on the body of the unit.

I should have included a pic showing all this:-

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