Discussion Category:  CO2 Incubator

temperature probe (thermistor)

Hello, I am looking for the information/dataseheet about the temperature probe used in the CO2 incubators of Thermo. The probe cat. number is 290184. It is a precision thermistor, 2252 Ohm @ 25 degrees C. However, this is the only information that I was able to find. I have an YSI 44004 thermistor, also 252 Ohm @ 25 degrees C and wonder whether it could be used as a replacement of an original defective part. Any information would be greatly appreciated. Anton.
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The problem is solved, so I will answer to my own question.  The original sensors (Thermo# 290184) were manufactured by UEC.  The item is long time obsolete.  Here are the parameters of this probe that I was able to find:

- NTC thermistor, nominal resistance 2252 Ohm @ 25 deg. C

- Operating range -50 deg. C to +150 deg. C.

- Tolerance 0 to 50 deg. C +/- 0.2%

The UEC were not able to provide the values of the beta or Steinhart-Hart coefficients for this thermistor.  However, the YSI 44004 thermistor has similar nominal resistance, operating range and tolerance.  So, we used the YSI 44004 to replace the original overtemperature protection (Thermo# 29018) and it works great.  All was needed is to solder a couple of wires to the new thermistor, cut off the original thermistor from the connector, solder the wires to the connector, place the heatshrink on leads and incapsulate the thermistor.  The original thermistor is incapsulated into the stainless steel tube; I used a heatshrink and some thermal glue to waterproof the part.  Epoxy could be also used but epoxy could absorb water with time, so I prefered to use the thermal glue.  It would be also possible to find a stainless steel tube of the apropriate diameter and put the thermistor into the tube.  I hope the above information could be useful for someboidy who has the similar incubators.  The thermistor deteriorate with the age and, although the original part is still available for USD 130.0-160.0, it will be also the old part manufactured 15 years ago.  The YSI 4404 is very cheap (probably USD 10.0-15.0) and commonly available.


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