Allegro Current Sensors

Discussion in 'General Electronics Chat' started by R!f@@, Feb 6, 2016.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    I am planning to buy this part.
    Need some basic confirmation.

    Before I decided to go with ACS750 but after seeing this part I want to use this.
    My Question is from the data, it says 20mV and 40mV sensitivity.
    I do not see how that works but I figured it could be that 3v to 5V Vcc part.
    Sensitivity is 20mV/A at 3V Vcc and 40mV/A at 5V Vcc. Am I correct here ?

    Next is about 50A ones and 100A (max Current ) Sensors... Interestingly 100A ones is bit cheaper.
    I am presuming the device output will stay the same for both ones.
    say if 40mV/A...out put for 5A will be 200mV increase for both 50A and 100A ones...Right ?
    If that is the case, would you suggest that I buy 100A ones ?
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    No. The 100 amp part is scaled at 20mV and the 50 amp part is scaled at 40mV. Look on page 2 for the part numbers.

    Digikey spells it out.

    http://www.digikey.com/product-search/en?keywords=acs756
     
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  3. crutschow

    Expert

    Mar 14, 2008
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    The higher amperage part will have less accuracy at low currents so you don't want to buy one with a higher current range than you need.
     
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  4. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Aaah!
    I need max around 30A worst. So I can stay at 50A.
    I guess 40mV/A is more accurate then ?
    I sit possible to measure in the 10mA Range ?
     
  5. Lestraveled

    Well-Known Member

    May 19, 2014
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    Nope. At 10mA the output would be .400 mV output. The noise output is 10mV (see spec sheet on page 5). This also means that 1/4 amp measurement would be very noisy.
     
  6. Lestraveled

    Well-Known Member

    May 19, 2014
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    @R!f@@
    What are you trying to do?
     
  7. Roderick Young

    Member

    Feb 22, 2015
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    Yes, and I would add that you should select a measurement range based on the peak current you intend to measure, not the average current. For example, let's say you have the part with a 20A full scale range. You have a signal coming in at, say 50 KHz, 30A, 50% duty cycle. You would hope that you get a reading of 15A, but in fact, the part will saturate, and the measurement will show 20A at 50% duty cycle, or 10A.
     
  8. Roderick Young

    Member

    Feb 22, 2015
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    Someone asked me this same question via email recently. If that was you, sorry for repeating myself, but one option, if you must measure currents in the 10 mA range, is to put two of these parts in series - one with a low range, and one with high.

    After you have done all you can to quiet the power supplies, you might still be able to get a reading from a signal that is lower than the noise, by averaging over a long period of time. This could be done with an analog filter on the output, or digitally with an average of many samples, or other digital filter.

    Are you trying to measure 10 mA and just trying to distinguish that from 20 mA or 0? Or are you trying to read 30A with 10 mA precision?
     
  9. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    I do not recall emailing any one.

    I am trying to measure Current from 0 to 10A to start with. I like to have 10mA resolution at best.
    That is the resolution I can get from a 10bit ADC of a PIC.
    I like the current measurement to be accurate.
    I never done this before so I am looking for possible options

    Is it possible to get accurate reading from Shunt resistors couple to a differential amplifier easily.
    Or do I need current to V converters.
     
  10. Lestraveled

    Well-Known Member

    May 19, 2014
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    @R!f@@
    I have been using this high side current sensor in place of hall effect sensors. It works very well. Much more accurate than a HE sensor. <$2.00 (I like it.)

    What is the common mode voltage range of the line you want to monitor?
     
  11. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Waitaminit..
    I got those thingies from TI sometime ago...I totally forgot about em...:D
    I checked the stock. I have
    INA199B3
    INA211A
    INA212A
    INA225A
    OPA340_2340_4340 Have each
    LMP8646

    I believe I already have what I need..Caramba !!! . I am getting old :(

    I need 60VDC max.
    Thanks @Lestraveled :)

    With these I can get 1mA resolution...Right ?
     
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