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February 25, 2013
about 2 years ago
I also had a need to measure bi-directional current, and after looking at the ina-169 datasheet and some trial and error, was able to do it with two of these boards after a small modification.
One board has the power leads attached as shown in the datasheet. The other board has its shunt resistors removed and no power leads attached. Then using short pieces of wire, connect the shunt resistor sense pad on the Vin side of the first board to the now-empty sense pad on the Vout side of the second board. Repeat for the other sense pads.
This configuration retains the same analog output values as a single board. Since you now have two separate boards each measuring current in a single direction, you also have two separate Iout lines. Refer to the examples in the ina-169 datasheet if you need to combine both signals into a single +/- signal line. For mine, I simply connect each line to an analog input on an Arduino and do the combining in software.
If you don’t want to remove the shunt resistors on one of the boards, then you will need to attach power leads to both boards, still connect the sense pads together as above, and then use the analog output parameter values for the next higher board in your code (i.e. for 90A boards, use the 18.3mV/A rating from the 180A board). Make sure the power leads on each side of the board are the same lengh between the board and where they ultimately come together, otherwise you may end up with slightly more current going through one board than the other which will skew your output.
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