The sensor on the Ranco ETC is a 30 kilo ohm Negative Temperature Coefficient resistive sensor or NTC for short.   This basically means that it is a resistor that will vary it’s resistance depending on the temperature and that it will read 30 K Ohms at 70 degrees Fahrenheit.   It also means that as the temperature goes up, the resistance will go down.

NTC sensors are typically rated at the resistance at 70 degrees Fahrenheight.  Unfortunately all 30K Ohm NTC sensors are equal.  Each model may have a different resistance at other temperatures.  This means that if you use just any 30K Ohm NTC sensor with the Ranco ETC, it will likely display the incorrect temperature most of the time.

To choose a compatible sensor you must compare the resistance at many different temperatures.  Click on the chart to the right to get the resistance at various temperatures for the ETC-1309007-044.

There is one possible replacement on the market we know of that comes in a variety of packages including air, surface, stainless and even a bare sensor.  This would be the Omega 44008 or 44032.  There are actually several different part numbers for the various packages  but all end in those numbers.  It is not a perfect replacement but over most of the temperature scale it is within 1/2 a degree of the original Ranco sensor.  Only at the bottom end of the scale (less than zero degrees) does it vary by more than a degree.   Omega publishes their temperature vs resistance curve so you can verify yourself if it will work for your application.   Search Omega.com for part number 44008 for more information on these sensors.