tim
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Posts: 3
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Post by tim on Sept 14, 2021 3:55:04 GMT -5
Hello,
I am using a Cernox sensor in the SD package (hermetically sealed) to measure the temperature inside of a hydrostatic Helium gas pressure cell. The sensor has survived a first test at 30 Megapascal (300 bar, about 4350 psi), but I worry that gas may slowly permeate the soldered hermetic seal, and thereby slowly change the resistance at constant temperature.
Is there any experience or expectation of how sealed SD package sensors behave under pressure?
Kind regards
Tim
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Post by Lake Shore Ryan on Sept 14, 2021 13:25:45 GMT -5
Hi Tim, first of all, thank you for linking to that publication. I hadn't seen this one and it's nice to have this to point to for future questions about this topic.
As for your application with the SD packaged Cernox, we don't have any data on what would happen to the various material boundaries under that combination of temperature and pressure, but we're interested to learn.
It sounds like you've already built the experiment and will likely proceed. If this is the case and would like to find out how that particular sensor faired, we could perform an internal vapor analysis at the conclusion of your experiment and let you know what we find. Obviously this would destroy the sensor, so we could arrange for a replacement if needed.
If you have space for additional sensors, we could also send extras that could all be installed together and gradually removed one at a time to see if/when helium begins to be seen.
We're open to collaborating on research like this. We often get questions from researchers about high pressure scenarios, so this kind of research could be helpful to others doing similar work in the future.
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tim
New Member
Posts: 3
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Post by tim on Sept 22, 2021 9:58:15 GMT -5
Hi Ryan,
Thank you very much for your fast response and kind offer.
The sensor I used for the pressure test was an old, uncalibrated Cernox of unknown type.
It may have been used in other experiments (though not under pressure) before, and I do not know whether it was previously subjected to mechanical stress which may have damaged the vacuum seal.
Therefore, I am unsure whether it would be worth examining that sensor.
I only used it to confirm that the SD package will withstand the pressure, having already destroyed an AA package, which imploded between 20 and 28 Megapascal.
Our pressure setup is still very new, and we need to resolve some issues before we can accurately measure the pressure at different temperatures.
I would suggest that I get back to your offer of testing multiple sensors at different pressures once we have built some confidence in our setup.
Kind regards
Tim
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tim
New Member
Posts: 3
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Post by tim on Sept 12, 2022 6:17:46 GMT -5
Hi, I just want to share some data on the pressure-dependence of the temperature readings of SD package Cernox sensors.
The attached PDF shows some data points I measured using my 30MPa Helium pressure cell. If the data are trustworthy, there indeed sems to be a small but significant pressure coefficient of the temperature readout, which is also temperature dependent.
Please treat this data with caution, though, as the experimental setup has not been designed to do this kind of measurements. Also, the data has not been published and is thus not independently reviewed.
Perhaps this data can be useful to someone, at least for order-of-magnitude calculations.
Kind regards Tim
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Post by Lake Shore Ryan on Sept 26, 2022 10:34:10 GMT -5
Hi Tim,
Great to hear from you again! Thanks for posting this data. It's at least good to see the sensor remaining functional during these high pressure tests. Did the sensor readings happen to return to baseline after being pressurized? Or were they permanent shifts? Thanks.
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