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I have tried to measure current using SparkFun Hall-Effect Current Sensor Breakout - ACS712 and also tried using shunt resistor. It seems that each measured value is different from what I measured by multimeter. And I don't know which one is showing the correct value.

Is there any simple solution for measuring a current? Also possibly more importantly, how can I test that the measured value is correct?

I want to start with a very simple circuit to test the current measurement and if it's verified that the measured value is correct, then I want to hook it up to the actual device, so that I don't damage the device accidentally.

Any suggestion is greatly appreciated.

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  • \$\begingroup\$ So, everyone knows it is possible, your multimeter appears to agree but, your undisclosed and therefore unseen-to-us measurement system does not. Where could the problem be? \$\endgroup\$ – Andy aka Sep 19 '15 at 17:02
  • \$\begingroup\$ Thank you for your comment. I was completely lost and thought all the circuits I put were wrong. I even thought that I might have accidentally destroyed the chips by ESD (electrostatic discharge) or by the heat of soldering. By the way, I used typical application circuit from ACS712 datasheet. \$\endgroup\$ – tadatoshi Sep 20 '15 at 1:17
  • \$\begingroup\$ Thank you for editing the link, Mahendra. I like your use of Markdown formatting. \$\endgroup\$ – tadatoshi Sep 30 '15 at 15:27
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Well the best beginner starting place is to use the shunt resistor and setup it up so you can use an A/D converter to make voltage readings of the drop across the shunt resistor. The simplest starting place is to have the shunt resistor connected to GND on one side instead of working with high side current measurement.

To get some correlation of readings you could easily use a digital volt meter to measure the voltage across the shunt resistor and also have it read what the A/D converter sees at its input.

The problem you can run into when trying to compare current measurements made by a digital multi-meter in current mode is that the meter itself has a shunt in side and this can change the amount of current flow in the actual circuit off enough to cause loss of correlation. Using the meter in voltage mode puts it in a fairly high impedance input mode thus keeping the meter from having as much influence on the circuit under test.

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  • \$\begingroup\$ Thank you for your answer. Your advice of using a digital volt meter to measure the voltage across the shunt resistor to get a correlation of readings has made me feel relieved. \$\endgroup\$ – tadatoshi Sep 20 '15 at 1:14

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