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I am measuring current of a 0.83mA with a Hall current sensor ACS273 100mV/A. I want to display this current as 8.3V. The problem is that in the datasheet of the ACS273 it is mentioned that no current output is 0.1*VCC=0.5V. at no current I want 0V. I have used opamp to get 8.3V from the output of ACS. how can I get rid of this extra 0.5V so that it does not get amplified. Ii also presume that no current voltage is added into the further voltages of ACS. i.e.

0.5V @ 0 Amp

0.5+y V @ x Amp

is it right?enter image description here

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  • \$\begingroup\$ Provide a link to the data sheet please. \$\endgroup\$ – Andy aka Jan 4 '17 at 11:33
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    \$\begingroup\$ Datasheet: allegromicro.com/~/media/Files/Datasheets/ACS723-Datasheet.ashx This is not a good choice of IC for measuring an 830uA current. It is unlikely that you will be able to make a measurement. The -05AB version would be a better choice, but it will still be difficult. \$\endgroup\$ – Jack B Jan 4 '17 at 11:41
  • \$\begingroup\$ please can you help me in picking an alternative? \$\endgroup\$ – tabs Jan 4 '17 at 11:55
  • \$\begingroup\$ and -AB is bidirectional and will give me 0.5*VCC=2.5V zero current output voltage \$\endgroup\$ – tabs Jan 4 '17 at 11:57
  • \$\begingroup\$ Do you have to use a hall sensor? Why not use a shunt resistor and differential amplifier? A hall sensor capable of reading small currents will be expensive. \$\endgroup\$ – Jack B Jan 4 '17 at 13:06
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Here's the main reason why your requirements are fairly pointless: -

enter image description here

Using the blue (nominal curve), a temperature drift from 15 degC to 50 degC takes the offset voltage from about 497 mV to about 499 mV - that's approximately 2 mV per 35 degC or 57 uV per degC.

And your signal is sitting on that drift with a value of 83 uV.

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  • \$\begingroup\$ is there any alternative to measure this current? \$\endgroup\$ – tabs Jan 4 '17 at 12:13
  • \$\begingroup\$ Basically you need a hall sensor that has a higher sensitivity. Trying to measure 850 uA in a full scale of 40 amps is problematic. \$\endgroup\$ – Andy aka Jan 4 '17 at 12:33
  • \$\begingroup\$ if i use -10AU its uni directional and its graph is quite stable.. will you recommend this ic? \$\endgroup\$ – tabs Jan 5 '17 at 9:02
  • \$\begingroup\$ Well, if you look at the graph in the data sheet what sort of drift problems does it cause. In other words, repeat what I did and ask yourself the question, if the ambient temperature moved 5 degC, will the effect of that swamp my signal? \$\endgroup\$ – Andy aka Jan 5 '17 at 9:18
  • \$\begingroup\$ is there any other way to do this task? \$\endgroup\$ – tabs Jan 17 '17 at 4:49

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