• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 45 subscribers
  • Views 705 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

noise found during thermistor measurement on ADS1220EVM using ADCPro

Ivan Chou61
Intellectual 350 points
Other Parts Discussed in Thread: ADS1220EVM, ADCPRO

I try to measure thermistor values using ADS1220EVM's RTD Terminal Block J2. And I follow the spec described in user guide

But there seems to have 60-Hz noise even if I enable FIR filter 50/60Hz Rejection

Any idea??

brief schematics

my setting; 

ADS1220EVM is powered by USB and AVDD is set to 5V. 

ADCPro setting:

MUX: AIN1:AIN2

OPERATION: Normal

Data Rate: 600 SPS

FIR Filter: Simultaneous 50/60Hz Rejection

PGA enable and set Gain = 1

Reference Select: External Dedicated

IDAC Magnitude: 10 uA

IDAC1 setting: AIN1

IDAC2 setting: off

  • 0
    TI__Guru** 113765 points

    Hi Ivan,

    The 50/60Hz rejection only works at 20sps.  At 600sps, 60Hz is well within the passband.  If you require the faster data rates than you will need to provide an external filter by changing the 0 ohm resistance of R1 and R2 to something that will create a low pass filter in combination with Cin_diff.

    However there are tradeoffs having large filter components both with noise and analog settling.  You could try values such as 4,7k resistors and a differential cap in the range of 0.33 to 0.47uF.  Also, you will need to drive the excitation current through a different path to avoid the filter resistor.

    Best regards,

    Bob B