Excitation voltage for Cernox

wei
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Posts: 2

Excitation voltage for Cernox Jul 24, 2018 12:20:01 GMT -5

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Post by wei on Jul 24, 2018 12:20:01 GMT -5

Hello, I am a graduate student using Cernox for my research project.

I would like to ask a question about some information shown in this webpage: www.lakeshore.com/products/cryogenic-temperature-sensors/cernox/models/pages/Specifications.aspx. I am wondering how the numbers in the Recommended excitation section (20 microvolts, 63 microvolts, etc) are determined. I read some parts of Appendix D and E but was not able to find out why those values were used in the calibration method.

I am sorry if my question has already been answered somewhere else. Thank you very much for your help!

Wei

Lake Shore Ogi
Lake Shore

Posts: 57

Excitation voltage for Cernox Jul 24, 2018 14:07:58 GMT -5 wei likes this

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Post by Lake Shore Ogi on Jul 24, 2018 14:07:58 GMT -5

Dear Wei,

As you may know, these values are conservatively set to minimize self heating especially in temperatures below 1 deg. K. These values were set based on many years of collecting sensor data.

Best Regards,
Ogi K.

wei
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Posts: 2

Excitation voltage for Cernox Jul 25, 2018 18:25:12 GMT -5

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Post by wei on Jul 25, 2018 18:25:12 GMT -5

Dear Ogi,

Thank you very much for your reply. After seeing your explanation, I read the "Self-heating" section in page 201 and looked at Table 6 in page 203 of the Appendix E, which nicely complemented what you explained. Thank you again!

However, I feel that perhaps I am not quite sure whether I understood the second paragraph of the "Self-heating" section... My understanding of this paragraph and the first one is that, the lower the temperature, the lower the thermal conductivity between the sensor and the object on which the sensor is mounted, and, as a result, Joule heating in the sensor does not quite cause the sensor and the object to thermalize with each other well, which leads to the sensor being hotter than the object. Is this more or less correct?

Thank you,
Wei