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I am using a hall effect current sensor. Its part number is ACS781LLRTR-050B-T from Allegro MicroSystems. In my circuit, I'm reading its output voltage to calculate current with MCU.

With no load, I read output voltage of current sensor as 2215 mV and use this value as zero current value. When the load is connected, it draws 2.3 A which means the output voltage of the current sensor must be 2286 mV, because the sensitivity of the sensor is 26.4 mV/A. However, in the MCU the voltage read is 2331 mV, which is higher than the expected 2286 mV.

What is the problem? What might be the solution?

Hall effect sensor datasheet

schematic of the related part of the circuit

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    \$\begingroup\$ Are you measuring an AC current? How do you know your current is 2.3 amps? \$\endgroup\$
    – Andy aka
    May 20, 2020 at 9:17
  • \$\begingroup\$ No we are measuring DC current. We measured current with external multimeter when load is connected. \$\endgroup\$ May 20, 2020 at 10:15
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    \$\begingroup\$ Be precise about this - what is the load and what is the supply that feeds the load. \$\endgroup\$
    – Andy aka
    May 20, 2020 at 10:18
  • \$\begingroup\$ Supply is 12.4 V DC power supply, load is custom 5.3 ohm. \$\endgroup\$ May 20, 2020 at 10:30
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    \$\begingroup\$ How DC stable is the 12.4 volt supply - what ripple voltages are present? \$\endgroup\$
    – Andy aka
    May 20, 2020 at 10:36

1 Answer 1

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We solved the problem. After trials with different loads (1A, 2A, 3A and so on), we realised that current sensor sensitivity is 36mV/A. We think that it might be because of the op-amp gains after the current sensor. Thank you all for your efforts.

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