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Differential signal amplify

Differential signal from Resistance  bridge(P3).  ADC is ADUC7060 Internal  .Consideration 4-20mA Circuit ,the power dissipation very low.Can only use ADA4051-2 Build Differential signal amplify. The scheme is ok?  In the debug,ADC1 ADC0 have 50HZ vpp 200mV Noise.Needs to go a step further filter?

How to filter out the noise(50Hz).


  You are taking a large amount of gain, so pc board layout is very critical to avoid noise problems.  At a minimum, you should make

provisions to add a capacitor across each15k resistor.  It is good that you have both common mode and differential mode R-C filtering

on the inputs.  What are the characteristics of the bridge?  Impedances, voltage or current drive (how much).  What are you measuring?

pressure?  weight?  How fast will the signal change?  If ten Hertz, you can apply heavy filtering to reduce the 50 Hz noise.  If the signal

frequency is higher, then layout and shielding is the only answer.


  • Harry:

           Thank you for your reply,What are the characteristics of the bridge?(Ceramic Pressure Sensors  )  Impedances(10K±20%)

    Re- establish parameter (look  Schematic.jpg)   Differential signal amplify'  95  times:

    For Common-Mode Rejection  and  Normal-Mode Rejection 50 Hz/60 Hz1
    On ADC Input:

    ADC :50 Hz/60 Hz ± 1 Hz, 16.6 Hz and 50 Hz update rate, chop on.(choose  16.6 Hz );

    ADCIN1 ADCIN2 waveform measurement (4.bmp)50Hz ;waveform measurement at the between of  C17(5.bmp) ;   waveform measurement at the between of  ADC0  ADC1  (6.bmp )  100Hz.      50Hz  to 100Hz  change(Why ?  )

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