• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 30 subscribers
  • Views 433 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.

TDC1000: maximum PT1000 resistance value that TDC1000 can measure

Oba
Genius 17295 points
Part Number: TDC1000

Hello,

 

There is the below note on page 7 of the datasheet(SNAS648B).

 

(4) PT1000 RTD approximate resistance: 800 Ω ≡ –52°C, 931 Ω ≡ –18°C, 1.10 kΩ ≡ 26°C, 1.33 kΩ ≡ 86°C and 1.48 kΩ ≡ 125°C.

 

Does it mean maximum RTD resistance value that TDC1000 can measure accurately value is 1.48Kohm?
If measuring over 1.48Kohm, is it still accurate?

My customer is considering to put a series resistor to PT1000 line for ESD protection.

 

Regards,

Oba

  • +1
    TI__Mastermind 23045 points

    Hello Oba-san,

    Thank you for your question. The testing conditions were not tested for a maximum resistance value, instead just tested for approximate values up to the max operating temperature of the TDC1000 (-40°C to 125°C). They were not tested beyond the operating range, so it is difficult to say how accurate a higher resistance might be. If the customer plans on using a resistor in series for ESD protection then this will alter the difference in resistance measured by the device and will most likely have to compensate when calculating the temperature.

    Keep in mind that RTD's respond differently and the formula used in the datasheet is a generic one so the RTD of their choice will likely have a better formula to use with their sensor of interest. The added resistivity might also just add a change that varies by the same rate so it might be simply add/remove an offset to the temperature measurement.

    The TDC1000 simply converts the resistance to a set of pulses to measure so I believe you should have a bigger margin to the resistance you may want to use but the formula provided in the data sheet will not work as intended with the added resistance. The customer would have to characterize their ESD resistor with the 1k reference resistor along with the RTD in order to develop a formula that fits their system.

    Best,

    Isaac