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I want to measure AC current with an Arduino-type device.

I am currently selecting a current sensor.

A 10 bit ADC gives 1023 points. At 5v that is 5v/1023 = 4.9mV

A current sensor with 185mV/A thus gives 26mA (4.9mV/185mV/A) per step.

A current sensor with 800mV/A gives 6.125mA per step.

Does this mean that current sensors with a higher mV/A are better in terms of accuracy of results?

(Obviously a ADC with more resolution would help)

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  • \$\begingroup\$ please recheck your calculations \$\endgroup\$ – jsotola Oct 8 at 4:28
  • \$\begingroup\$ Your units are off. V / (V/A) gives A \$\endgroup\$ – nabulator Oct 8 at 4:36
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Yes.

There is a trade off between range and precision of measurements in any ADC setup. Since current sensors only give us sensitivity in V/I and we care only about I, sensitivity is inversely related to precision. This also makes sense as more sensitive sensors ought to reflect smaller changes in current.

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For reasons of power dissipation and voltage load regulation , the most common current shunt chooses the R value to be 50mV at max current. (More or less) Then choose the Pd rating for the resisitor to be 2x pwr of 0.05V*I for 50% reduction of 120’C rise in temp. of the resistor.

This is also used in high side current sense IC’s which use analog parts that operate at Vdd common mode range with high gain.

Thus you can lose only 50 mV and get your desired current range with gain with 1000 steps/x Amps or Amps/1000 per step.

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