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I am looking for an alternative part to replace an existing thermistor (type: Thermistor NXP KTY83/122 SOD68 1.02kohm). This part appears to be discontinued so that's why i need an alternative. I will be using it to measure motor temperature (Brushless DC motor), the sensor will be connected to the BLDC motor controller (which is designed to work with this particular thermistor). A max temp. rating of approx 150celcius would be desireable I think.

I am not sure what specs/details to look for when searching for a suitable alternative. Would any PTC with same Resistance @ 25 °C, a somewhat similar Thermal Time Constant, and approximately the same temperature ranges (max and min working temperature) be suitable? I was looking for a number indicating how much the resistance changes per Celcius temperature increase/decrease for a certain thermistor and came accross the "TK" aka "Temperature coefficient" value in the datasheets? Is my assumption correct that this value indicates how much the resistance changes per increase/decrease of temperature?

Datasheet of original part: https://docs.rs-online.com/4af3/0900766b812d0c2e.pdf

Perhaps this is a suitable alternative?:

part name: NXP KTY81/110,112 Thermistor SOD70 1.01kΩ datasheet: https://docs.rs-online.com/17a2/0900766b812d0c2c.pdf

  • Similar resistance @25C (1,01kohm compared to 1,02kohm for the original part)
  • Max working temp=150 Celcius (should be enough for my purposes)
  • Similar temperature coefficient (0,79 %/K for this part compared to 0,76 %/K for the original part)
  • Resistance ratios listed in datasheets also look quite similar (although I am not really sure what this means/if it is important)
  • Thermal time constants are higher at 3/5/30seconds instead of 0,5/1/20seconds (flowing liquid, still liquid, air) but I think that shouldn't be an issue for my applications since I'll be gluing the sensor directly to the aluminum core of the motor (so it should eb comparable to the thermal time constant value for "still liquid") and there shouldn't be any rapid temperature changes in the motor so a delay of approx 3 seconds is acceptable

What approximate inaccuracy in temperature measurement do you think would result from replacement of the original part with the alternative mentioned above (since it has slightly different values), will the inaccuracy be significant? (more than 2 Celsius for example)?

Thank you very much for any input, it is greatly appreciated :)

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  • \$\begingroup\$ Without knowing the exact circuit it is being used in, this question is unanswerable without guesswork. \$\endgroup\$ – Andy aka Sep 7 '20 at 16:29
  • \$\begingroup\$ @Andyaka it will be used in combination with the following BLDC motor controller: Sabvoton SMVC72150 .. not sure if that helps. will try to get electrical scheme from supplier. \$\endgroup\$ – Maarten -Monica for president Sep 7 '20 at 16:32
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    \$\begingroup\$ While you are doing that ask them for a recommendation. \$\endgroup\$ – Andy aka Sep 7 '20 at 16:33
  • \$\begingroup\$ @Andyaka yes, will do that \$\endgroup\$ – Maarten -Monica for president Sep 7 '20 at 16:33
  • \$\begingroup\$ @Andyaka I have received a recommendation for alternative component from motor controller supplier. thank you for the suggestion. I have posted the possible alternatives i got suggested/i have found in an answer below. \$\endgroup\$ – Maarten -Monica for president Sep 8 '20 at 18:21
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Suitable alternatives:

  • NXP KTY81/110,112 Thermistor SOD70 1.01kΩ, 5.2 x 4.2 x 4.8mm (very similar specs, slightly bigger casing)
  • KTY83-122 silicon temperature sensor (recommended by bldc motor controller supplier/seller)
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