I am using Lakeshore Model 240 for interfacing PT-100; However as per the specification i see that IEC 751 is implemented in Model 240 which is defined only until (-200 degrees C) in the standard.
As we know PT-100 can measure lower temperatures also and the sensor which i am using is a calibrated sensor calibrated from 14-325K. In such case should i load the calibration data to Model 240 for the lower temperature regime or how does 240 behave when measuring say 50 kelvin with no calibration data loaded to it.
I have mounted PT-100 on to one of the cryocoolers capable of working from 300 to 20 kelvin.
I am asking this question since i am not sure how to configure the transmitter for this case.
Appreciate your quick reply. Let me know if you need more information.
Post by Lake Shore Jeff M on Jan 8, 2019 8:48:28 GMT -5
The MeasureLINK software that you will use to configure the Model 240 actually has two different PT-100 standard calibration curves that you can select. As you indicated, the IEC PT-100 curve cannot measure temperatures below 73.15K (-200C) where the LSC PT-100 curve will read down to 28K.
Using the IEC curve, any temperature below 73.15K will produce a T. Under error and the LSC curve will produce the same error at temperatures below 28K (-245.15C).
However, since you do have the calibration files for your sensor, I recommend that you load that file into the Model 240 for best accuracy.
Post by Lake Shore Ryan on Jan 8, 2019 9:58:51 GMT -5
Just for a little more context, the IEC 60751 curve is defined by a fairly simple formula from -200 to 0 °C. Our PT-100 curve is based on our particular 100 Ω wire-wound platinum sensors and will give you more accurate temperature measurements if using uncalibrated PT-100 sensors. The offsets between IEC 60751 and our PT-100 curve are small (10s of mK), but noticeable with the 240 Series modules. This offset gets worse at temperatures above 0 °C.
So in the end:
Uncalibrated generic 100 Ω platinum sensor - use the IEC 60751 curve built into MeasureLINK
Uncalibrated PT-100 sensor from Lake Shore - use the PT-100 curve built into MeasureLINK
Calibrated PT-100 sensor (both SoftCal and full calibrations) - load unique curves to 240 module using MeasureLINK
Ryan Oliver Product Manager, Sensors and Instruments Lake Shore Cryotronics