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Test of the Current Sensor

A project log for Simple, Compact Wireless Measurement

Measure, probe, and monitor voltage and current remotely!

Ben LimBen Lim 08/03/2021 at 13:080 Comments


This is a MAX9938 NanoPower Op Amp being tested. Because I didn't want to make a whole new circuit just to test this, I decided to use a breakout board for an SOT23 footprint, and then soldered a 0805 5R6 resistor across the terminals. It is put in series with a 1k resistor, and the output was 0.923V. I measured the resistance across the terminals of the current sense resistor and it was 5.7 ohms. The voltage is scaled by 50.

Calculations

V = 0.923 V / 50  = 0.01846 V

V = IR

I = 0.01846 / 5.7 = 0.003296A

Given that voltage is 3.3V, and measured resistance is 983

Vb = 3.3 - 0.01846 = 3.28154V

R = 983 ohms

I = 0.003338A

Percentage error = (0.003338 - 0.003296) / 0.003338 =  1%

Conclusion

It is not a fantastic result, but it does work for our simple measurement purposes.

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