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ADS112U04: ADS112U04IPW

Part Number: ADS112U04

We use the ADS112U04IPW to measure 4-20mA current from a sensor.  The value we get back from the ADS112U04IPW does not match our lab bench current meters.  Error is about 4% and it is non linear.  2K resistor is equivalent to our customer's sensors.  The LED is there so we can see if we have a good current loop.  Display is a lab bench current meter. 

We run the current through a 100 ohm resistor and measure the voltage drop across it.  Checksum is good and results appear to be good but accuracy and linearity is bad so we must be doing something wrong.

raw=buf[1]<<8+but[0]

ma=2.048 * (rawhex/7FFF)*10.

  • Hi Peter,

    This issue is seen when using the PGA in the enabled state. When making single-ended measurements with the ADS112U04, the PGA must by disabled and bypassed. With the PGA enabled (default state) the PGA amplifier output cannot drive all the way to ground. The setting for the PGA is in Register 0, bit 0, the PGA_BYPASS. This bit should be set to 1.

    Best regards,
    Bob B
  • Hi Peter,

    If you think you are properly configured, can you please send me your configuration register settings? Also, please send me the data you are getting and the external measurement you are seeing so that I can compare. Please send raw code values and not calculated values from the ADS112U04.

    Best regards,
    Bob B