• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 192 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.

Original question:

ADS114S08: Issue with Random Values from ADS114S08 When RTD Sensor is Not Connected

ADS114S08: ADC Inquiry

Nikhil Batra
Prodigy 50 points
Part Number: ADS114S08

Tool/software:

Hii Team,

We are using the ADS114S08 for RTD temperature measurement and encountering an issue. The device works correctly and provides accurate temperature readings when all four channels are connected simultaneously. However, when any channel is disconnected, the next channel shows inaccurate values.

For example, when the RTD on channel 3 is removed, the values on channel 4 become distorted (off by 2 to 3 degrees). Similarly, when the RTD on channel 2 is disconnected, the values on channel 3 are affected.

Additionally, when we attempt to read the ADC in reverse order (channel 4-3-2-1), the value of the previous channel gets affected.

Could you please help us identify the cause of this issue and suggest a possible solution?

Attaching schematics for reference. (Pull together resistor of 1Mohm is DNP)

SCHEMATIC_SCU MICROCONTROLLER CARD REV B(2MM).pdf

Thanks

Nikhil Batra

  • 0
    TI__Mastermind 45785 points

    Hello Nikhil Batra,

    It is the weekend now. The support engineer will respond your query early next week.

    BR,

    Dale

  • 0 in reply to Dale Li
    TI__Guru 52496 points

    Hi Nikhil Batra,

    Your input circuitry has a super low cutoff frequency, at around 10Hz. This is going to take too long to settle every time you switch inputs. The settling time to ~99% is around 75ms.

    You should increase the filter cutoff frequency by reducing the size of the resistors and capacitors.

    I mentioned this in the other post that you referenced, from your colleague Prashant

    -Bryan