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Using calibrated Cernox above calibration range

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fanx42
New Member

Posts: 3

Using calibrated Cernox above calibration range Aug 2, 2019 5:51:45 GMT -5

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Post by fanx42 on Aug 2, 2019 5:51:45 GMT -5

Hi, looking for advice here.
I use calibrated Cernox 1080 CX-SD in combination with controller 335 and heater wire for application around 90K. That is fine...
But sometimes I would like to heat up the system to bake out some chemical residues. The problem is that I need to go to approximately 360K when calibration of the Cernox ends at 325K and the controller does not allow me to set a setpoint above this temperature.

The datasheet states that the sensor can withstand up to 500K bakeout but is it possible to use it for measuring at about 400K?
I do not need to be very precise in this range, so what if I just manually extrapolate the calibration curve?

Thanks, Frantisek

Lake Shore Jeff M
Lake Shore

Posts: 327

Using calibrated Cernox above calibration range Aug 2, 2019 8:12:59 GMT -5

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Post by Lake Shore Jeff M on Aug 2, 2019 8:12:59 GMT -5

Hello Frantisek,

The maximum temperature for a Cernox High Temperature sensor is 420K. Although the SD package sensor may withstand a higher temperature for a short duration, it is not recommended that it exceed 420K.

Since your sensor was calibrated to 325K, the setpoint limit in the curve is set to that value. In order to raise the temperature above this limit, you will need to modify the sensor curve to change the setpoint limit to 400 or 420K and insert an additional curve breakpoint at the beginning of the table. Note, the value you need to input is the LogOhm of the resistance and temperature in K.

If you have any questions or need help in determining what to add, let me know the serial number of your sensor and I will provide a suggested value to input.