Cernox sensor is not matching the calibration curve.

Vinay,

You do not say exactly what the difference is so it is hare to determine what may be causing the issue. I have some questions:
1. What curve did you load into the Oxford Controller
2. Are you only using 2-wires for the connection or does the Oxford controller use the 4-wire concept?
3. What is the serial number of the sensor
4. What is the room temperature resistance of the sensor?
5. Does the Oxford controller offer the reversing option?

Since we do not make the Oxford controller, I do not know how it works so I cannot tell you if you are connected correctly or not.

The recommended excitation voltage for a CX-1030-CU-1.4L sensor is 10mV. We calibrate a large numbers of sensors at the same time, therefore we excite the sensor at a much lower excitation voltage than the recommended value to eliminate any possibility of heating due to the sensors.

Depending on what temperature your sensor is at, what you are measuring on your multimeter is close to what you will see when making a 2-wire measurement using a multimeter. Each of the 36" long leads adds approximately 10 - 11 ohms so if the sensor is at 36+ ohms and each lead is 10+ ohms, your 59-61 ohm reading is close. To determine exactly how much lead resistance will be added you can measure I+ to V+ and I- to V-, add the result together and then divide by 2. That amount will be added to the resistance of the sensor when making a 2-wire measurement. Can you display the sensor value on the Oxford Controller to see what it is reading?

Reversing is a feature offered on Lake Shore controllers that reduce EMF build up in the leads. When reversing is active, the excitation current is reversed with every other measurement. When this is not an option, EMF build up can cause the readings to be higher than it should be.

Let me know what temperature you are seeing on the Oxford controller and what calibration table you used to enter the resistance versus temperature in the controller.

In order to interpolate the correct temperature, the exact sensor value needs to be used. Controllers measure the resistance and then interpolate the temperature by doing a straight line interpolation between the adjacent curve points to what was measured. If the resistance used for the interpolation is not correct, the interpolated temperature will also not be correct.

Exactly what is teh temperature difference in the reading on the Oxford controller versus what you believe the temperature is?

Basically, the difference between the resistance at 305 versus the resistance at 293 is less than 1 ohm. At 305K, the sensor would be at 36.27 Ohms and at 293K it would be 37.15 Ohms so you do need to adjust the Oxford for any offset to get an accurate reading.

Lake Shore controllers are calibrated and do not require any offset adjustments when sensors are connected.