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PGA of ads1014

Frank Shao
Prodigy 50 points
Other Parts Discussed in Thread: ADS1014

I want to use ADS1014 in differential input mode to measure 4-20mA current loop whose load is 20 omhs and the supply is 3.3V.  According to Table 3. PGA Gain Full-Scale Range on page 10 ,  I can only set PGA to 1 or 2 . Is it correct? My another question is that connecting AIN0 to VDD through 1M resistance and AIN1 to GND through 1M resistance, can ti work?

  • 0
    TI__Guru** 113765 points

    Frank,

    If I understand you correctly you want to measure the voltage across the 20 ohms.  Is that correct?  If it is, then the maximum voltage will be 0.4V and you could use PGA setting of 8.

    I'm not sure why you want to add the 1M resistors unless you are trying to bias up the voltage to mid-supply.  In this case you would reduce your range to PGA 1 or 2, and increase your error as you add another current path.  I would simply take the measurement across the 20 ohm resistor.  This assumes that the grounds are common to both the ADS1014 and the 4-20mA current source.

    Best regards,

    Bob B