logo elektroda
logo elektroda
X
logo elektroda

AD8628 Op Amp Non-Inverting Amplifier Not Providing Expected Gain with 0-3V Rail

12 12
ADVERTISEMENT
  • #1 21682925
    Scott Siler
    Anonymous  
  • ADVERTISEMENT
  • #2 21682926
    Martin Rowe
    Anonymous  
  • #3 21682927
    Martin Rowe
    Anonymous  
  • ADVERTISEMENT
  • #4 21682928
    David Ashton
    Anonymous  
  • #5 21682929
    Richard Gabric
    Anonymous  
  • #6 21682930
    Scott Siler
    Anonymous  
  • #7 21682931
    Scott Siler
    Anonymous  
  • #8 21682932
    Sanjay Meena
    Anonymous  
  • ADVERTISEMENT
  • #9 21682933
    David Ashton
    Anonymous  
  • #10 21682934
    Richard Gabric
    Anonymous  
  • #11 21682935
    Scott Siler
    Anonymous  
  • ADVERTISEMENT
  • #12 21682936
    David Ashton
    Anonymous  
  • #13 21682937
    Steven George
    Anonymous  

Topic summary

An aerospace engineer is attempting to amplify the 0-36 mV output from a commercial strain gauge load cell powered by a 12 V excitation to better utilize the input range of an NI 6289 DAQ, which has a minimum input range of ±100 mV and 18-bit resolution. The engineer used an AD8628 precision op amp in a non-inverting amplifier configuration with a gain of 3 but observed no expected gain; the output voltage was lower than the input. Responses clarified that strain gauges are passive devices requiring excitation and typically produce differential outputs from a Wheatstone bridge, necessitating a differential or instrumentation amplifier rather than a single-ended non-inverting amplifier. The common mode voltage from the 12 V excitation is about 6 V, which must be considered in the amplifier design. Suggestions included using a differential amplifier stage, ensuring proper wiring, and considering ratiometric measurement techniques where the ADC reference drives the load cell to improve stability and accuracy. It was also noted that the load cell output after amplification might exceed the DAQ input range, so gain or excitation voltage adjustments may be necessary. Temperature stability and noise were considered manageable in the described environment. Additional advice included reviewing op amp tutorials on differential amplifiers and carefully designing the front-end to match the required resolution and stability.
Summary generated by the language model.
ADVERTISEMENT