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ADS122C04: Response with very high deviance from ADS + pressure sensors

user6546178
Prodigy 10 points
Part Number: ADS122C04


Hello,

I use ADS122C04IPWR with 4 pressure sensors.
Honeywwell;
1 x SSCDRRN060MDAA5 Difrerential ±6kPa
1 x HSCSAAN010NDAA5 Difrerential ±2.49kPa
2 x SSCDANN015PAAA5 Atmospheric.

I use,
kirk.setGain(ADS122C04_GAIN_1);
kirk.enablePGA(ADS122C04_PGA_DISABLED);
kirk.setDataRate(ADS122C04_DATA_RATE_600SPS); ( I also tried with all options)
kirk.setOperatingMode(ADS122C04_OP_MODE_NORMAL);
kirk.setConversionMode(ADS122C04_CONVERSION_MODE_CONTINUOUS);
kirk.setVoltageReference(0x2);
kirk.enableInternalTempSensor(ADS122C04_TEMP_SENSOR_OFF);
kirk.setDataCounter(ADS122C04_DCNT_DISABLE);
kirk.setDataIntegrityCheck(ADS122C04_CRC_DISABLED);
kirk.setBurnOutCurrent(ADS122C04_BURN_OUT_CURRENT_OFF);
kirk.setIDACcurrent(ADS122C04_IDAC_CURRENT_OFF);
kirk.setIDAC1mux(ADS122C04_IDAC1_DISABLED);
kirk.setIDAC2mux(ADS122C04_IDAC2_DISABLED);

I supply the sensors and ADS with 5.066 V constantly. But I'm getting responses from all of this sensors with very high deviation.
I apply linearization in -2490 Pa to + 2490 Pa with the value that I got from ADS via a qualified reference pressure calibrator. Even I don't touch to sensors, I'm getting values in a wide range such as -200 to +200 Pa. Just in a second I see 70Pa, -50 Pa 120 Pa 0 Pa etc...
Example outputs from ADS just in a second.
4187657
4185123
4191087
4190261
4188744
4190720

Output from the pressure sensors to ADS is stable.
Supply voltage is stable and constant. I think my issue is about ADS. Output from the ADS is not stable. What could bu the problem?


Thanks in advance.

  • 0
    TI__Guru** 113765 points

    Hi user6546178,

    Welcome to the E2E forum!  It would be helpful to know more about your system and the setup.  Do you have a schematic that you can share?  Are you using a prototyping solution?

    Generally these types are measurements are done ratiometrically where the pressure sensor excitation is the same as the reference voltage for the ADC.  There are many sources for noise pickup besides the reference noise.  This can come from cabling between the sensor and the ADC and the source is EMI/RFI.  If the setup is a prototyping solution, then often the wiring of the prototype can also be an issue.  Also, you should have some analog input filtering to help with noise reduction and antialiasing.

    What would be helpful for me to help troubleshoot your setup would be to see the schematic and to know the precise input voltage being measured (as opposed to pressure).  A data set showing at least 128 consecutive and contiguous samples as raw data (hex preferable to decimal) will help to determine the total noise.

    Another thing you could do would be to check the noise using the mux setting for an internal short ((AVDD-AVSS) / 2).  This will be the ADC noise itself and you should be able to match very closely to the noise tables shown in the datasheet.

    Best regards,

    Bob B