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Probe Immersion Depth calculation

Title:     What is the minimum immersion depth for my probe?

Created:  20.May.2013

Last Revised:




Applies To:  All metal sheathed PRT's / RTD's


Problem Description:  The probe is reading off at smaller immersions.  How deep must the probe be immersed?


Resolution/Work Around:  Use the following formula to help calculate the immersion depth.  This is used as a good rule-of-thumb to help eliminate the stem conduction errors.  


Immersion Depth = Sensor Length + 20 times the diameter of the sheath


You should do some experiments with your own sensors to establish their optimal immersion depth.  Thermometers with low stem conduction errors make good references for checking the uniformity of heat sources.


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