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PZEM-031 power display:




This is a great little digital meter that will measure voltage, current, watts, AND count up watt-hours. It
also has a blue backlight for the LCD that can be turned on/off. The meter is sold in two configurations:
one with a built-in shunt that measures up to 20 amps, and the other using an external shunt that measures
up to 100 amps. This display is sold under several brands, including PeaceFair, HiLetgo, and DROK.

This meter will work from 4.5 to 100 volts, and is powered off the same line that is measured. Precision is
0.01 volts, 0.01 amps, and 0.1 watts, with precision for the 100 amp external-shunt version being 0.1 amps.
This is one more digit of precision than the common black rounded inline meters. (which don't hold Wh)

There are no adjustment trimmers on the board. Self-calibration can be triggered by following the steps found
in the menu instructions link below.

The watt-hours count is saved when the meter is powered down, and will resume counting when powered back
on, so you will need to clear the Wh counter when starting a new session. (also in the menu instructions link
below)

This meter requires a fair amount of depth in your enclosure, but you can pop off the back cover and carve
down the side walls of the housing pretty easily to cut the required depth in half. The green power connector
can also be removed to make a little bit more room if necessary.

Waterproofing is a little problematic. My first inclination was to remove the LCD/board from the housing and
lay down a bead of silicon around where the LCD fit in and then re-assemble it, but I neglected to deal with
the reset/function button on the front. In later installations, I just sealed around where the housing met
my enclosure, and spread down a strip of clear packing tape across the whole display including over the reset
button. This keeps things pretty water-tight while allowing me to continue using the reset button. The pic
above demonstrates my "packing-tape waterproofing".

I also considered installing smoky plexi over the top to cut down on glare and improve visibility in direct
sunlight, but I found this was unnecessary with the display's adjustable backlight.


meter shunt adjusting

operating the meter's menus

power display 100v 20a ($15 at Amazon)



last updated 02/05/2025 at 20:51:09 by make_www_index.command version 2025.01.29.A