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I am designing a circuit with allegro current sensor ACS770 for measuring currents up to +/- 90A. I have 2 options :

  1. use single ACS770-100B (100A Bidirectional version)
  2. use dual ACS770-50B in parallel as suggested in :

Using Allegro Current Sensor ICs in Current Divider Configurations for Extended Measurement Range

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Since my focus in on accuracy i am inclined to use option 2. However I cannot get my head around this : will accuracy increase , decrease or stay the same ? (resolution will be better obviously)

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  • \$\begingroup\$ Peripheral: be CERTAIN that the devices can never be destroyed thermally by overcurrent. If they melt down electrical isolation can be lost with potentially disastrous results. \$\endgroup\$
    – Russell McMahon
    May 11, 2021 at 7:59
  • \$\begingroup\$ Could you please confirm if you are building a single device or if this is a project to be manufactured in series and if there is going to be a calibration process, with adjustment (by software and/or hardware)? \$\endgroup\$
    – devnull
    May 11, 2021 at 15:36
  • \$\begingroup\$ @RussellMcMahon . thank u for the heads up . I actually didn't know that and i am shocked \$\endgroup\$
    – Eng Sam
    May 11, 2021 at 16:12
  • \$\begingroup\$ @vangelo , the maximum number of unit to be built is around 70 pcbs . regarding calibration , honestly i am not very familiar how it is done and what setup i would need . but please advice how would it help ? and how it should be done \$\endgroup\$
    – Eng Sam
    May 11, 2021 at 16:15
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    \$\begingroup\$ @EngSam Accuracy, Precision and Error have specific meanings so I was attempting to be sure of the actual needs. As shown in the table you posted there are different sources of error in the sensor and this device is only one piece in the whole system. When you put them all together some of them can be minimized by making adjustments or compensating in software. Other errors will remain and the overall accuracy may even get worse with time. Summary: calibration with adjustments would help by reducing systematic errors down to the accuracy of the calibration procedures themselves. \$\endgroup\$
    – devnull
    May 11, 2021 at 16:35

1 Answer 1

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Relative accuracy will stay the same.

You need to combine the two current outputs with the same gain.

If the current split between the two devices is not equal, and varies (either with time, temperature or from batch to batch) and the output gains are not equal, then you will have a gain variation.

The poor man's version of this is to use an unmeasured current shunt bypassing the current shunt. An even poorer version would be to use a metal conductor of some description bypassing the measuring shunt. However, if this metal is not matched in tempco to the current shunt, you will get significant changes of gain with temperature.

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  • \$\begingroup\$ So my concern was legit . Accuracy will not increase , and there is no benefit. regarding your poor man's version , (using a shunt in parallel) resolution will be decrease by half , assuming Shunt and current sensor have same resistance. \$\endgroup\$
    – Eng Sam
    May 11, 2021 at 16:17
  • \$\begingroup\$ If i need better accuracy I shall use another hall effect sensor ( closed loop ) correct ? \$\endgroup\$
    – Eng Sam
    May 11, 2021 at 16:18

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