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I am wondering how the DHT 22 (measures humidity and temperature) sensor would work under double or triple atmospheric pressure (rough calculations have been done but it will vary and the exact density being dealt with is not currently known).

The sensor is being considered to be used for a project I am involved with where the temperature of grain in a bin would be monitored to help prevent the spoiling of the grain.

The project's small GitHub is located here https://github.com/PhysicsUofRAUI/binTempSensor , I don't think any more useful information is there but maybe I'm wrong.

The project has a few different ways to communicate (only a few may eventually be made), but it will all be done at atm pressure so it is irrelevant in this question.

I am also curious in general about how sensors would act in these situations, so if anyone has any knowledge they want to share that'd be awesome.

Would it cause parts of it to break? Could other adverse things happen?

Cheers and thanks!

  • why would the pressure inside the grain bin be higher than atmospheric pressure? – jsotola Dec 5 '18 at 8:41
  • It is because in the bin the sensor will have layers of grain on top of it, so the pressure will go up with this equation (density)x(gravitational acceleration)x(height). The sensors I am worried about are in the middle and bottom (say 10m to 15 or 20m of grain on top). Depending on the density the pressure will go up a bit. Here is a link with the equation I said [hyperphysics.phy-astr.gsu.edu/hbase/pflu.html] – Kody Rogers Dec 6 '18 at 18:09
  • i find it difficult to believe that the air pressure at the bottom of a grain pile is any higher than atmospheric pressure .... the grains cannot possibly create a perfect air seal .... i could be wrong, of course – jsotola Dec 6 '18 at 18:36
  • @jsotola: people drown/suffocate in grain elevators all the time, they are very dangerous. – dandavis Dec 12 '18 at 20:03
  • the humidity readings would be off, but should be consistent (you can compensate) – dandavis Dec 12 '18 at 20:04
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The sensor is in a hard plastic case with holes to allow the air in to measure temp/humidity

The inside of the case will be at atmospheric air pressure, the problem will be the force on the outer case and if this will be high enough to cause it to break and cause it to press on the internal components.

I think the only real option here will be test one (the sensors are cheap enough to destructively test one)

  • I will do this when I get back home and let you know. Thanks! – Kody Rogers Dec 6 '18 at 18:11
  • Hello. Just an update. I did this and found that the sensor held up fine. I calculated the force that would be applied in the bin from the pressure. It turned out to be quite small because the sensor itself is small and it was easy to test. Thanks! – Kody Rogers Jan 16 at 21:28
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I don't think it's a good idea to work at a higher pressure than the nominal one, in any case, if the device could work in those conditions, it would be specified in the datasheet and that information doesn't appear, therefore I assume that the nominal pressure is 1g.

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The correct phrase is not pressure, but external force applied on top of the sensor.

One way to verify (if you can afford) is to actual test that external load on its readings.

Other way is to install it in a casing that will absorb external load. This casing needs to be with holes to able temp and humidity go through.

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