I've been needing a amp gauge to mount near my controller and I seen one on eBay for less than $5 shipped to my door. About a week later it arrived so I went out to test and play with it. I connected it to a 4 amp DC light and it pegged the 20a meter. It was connected proper but it had no shunt resistor.
I tested resistance of the meter and it ended up being 75mV.
Now I needed a shunt.
I had a piece of #12 copper wire (and with help) was able to determine the spacing of the meter leads to solder to this piece of 12ga wire. Here's how it went:
#12 is 1.588 / 1000' 0.001588 ohms / foot
75mV / 20A = 0.00375 ohms
.00375 / 0.001588 =
2.36', or 28.34" space between leads of the amp meter soldered to the #12
I used my HF meter to check the amps of a DC source and compared that to the meter reading on my analogue DC amp meter. They matched almost exactly at 4 amps.
Close enough to see how many amps my 5'7" dual rotor is putting into the battery.
Cheap and effective.
(Thanks Glen....)
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