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Problem using INA2126 to amplify differential voltage from RTD

Prodigy 80 points

Replies: 3

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I'm trying to amplify the voltage from an RTD (resistance temp device) using one amplifier on INA2126 using a single 5VDC supply. The circuit is attached. The 0.1VDC voltage for pin1 Is obtained from a precision voltage divider. However, on the output I only get a 0.2 mV signal whereas my input differential voltage is around 20mV and Rg was selected for greater than x100 gain. Could you tell me where I'm going wrong?

Appreciate your help.

3173.RTD_INA2126.PDF

  • IN2126 will not work on single supply.  Use INA333.

    Tim Green, SMTS
    Precision Amplifiers Applications Manager
    
    		
  • Hello Adnan,

    The input common-mode of your signal is near ground, which is outside of the linear operating region of the device. Please see the graph of input common-mode range vs. output voltage on page 4 of the data sheet (lower right corner).

    So, you have a few options here. First, you could put your RTD in a Wheatstone Bridge configuration. Please see slide 8 of the attached presentation.

    Secondly, you may be interested in evaluating the INA326, which has rail-to-rail input and output swing.

    Finally, we have integrated solutions for temperature sensing. Here are some examples: ADS1118, ADS1220, and ADS1247.

    Regards,

    Pete Semig

    Applications Manager, General Purpose Amplifiers

    Analog and Digital Sig Con for RTD Sensors_clean.ppt
  • In reply to Pete%20Semig:

    Thanks, this helps a lot.

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