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Pyportal temperature inaccurate
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Pyportal temperature inaccurate

by astrouga on Tue Jun 30, 2020 2:49 pm

We finally got around to opening our Adabox 11 and setup our Pyportal as a smart thermometer following the guide and code here: https://learn.adafruit.com/pyportal-sma ... n?view=all

The temperature seems to be off by as much 10 degrees. It is constantly displaying between 82 to 85 degrees in a 75 degree room in the shade. The screen is also not in use and the sensor is not obstructed in any way. Measuring the temperature across the board, it appears that the board is just too hot. Do I have a bad board, or is this temperature sensor notoriously off?

astrouga
 
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Re: Pyportal temperature inaccurate

by siddacious on Wed Jul 01, 2020 12:07 am

Are the measurements consistent? Do you have your pyportal in a case? If the room goes up a few degrees, does the value measured by the pyportal go up the same amount?

The ADT7410 temperature sensor on the PyPortal is a nice sensor, accurate to within 0.5 degrees celsius and I double checked that the library is working to the specifications laid out in the datasheet. I also compared my PyPortal against a known good thermometer and as it turns out my room is measured at 75.7 degrees F and the PyPortal is reporting 28.25 C / 82.85 F. I suspect that the board/sensor is actually the measured temperature but that there is an offset from the room temperature due to differences between how the room and sensor's environment are being measured.

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Re: Pyportal temperature inaccurate

by astrouga on Wed Jul 01, 2020 12:09 pm

siddacious:

First, thanks for helping!

We removed the PyPortal from the stand that came in the Adabox as soon as we noticed the high temperature. I believe that brought the temperature down a few degrees F. We've also turned the touch display off as that seems to generate additional heat that increases the reading too. Also, we have positioned our PyPortal 'display down' on the table so that the temperature sensor is facing up with no obstructions. In this situation, we see a pretty consistent temperature measurement.

The issue is that the temperature reading is not representative of the space around the device. The temperature appears to be too heavily influenced by the temperature of the board. It seems like your measurements match up with mine though - I have a 75 degree F room and an 83 degree F reading from the PyPortal. What is the intended solution? Is it to assume the temperature offset is fairly consistent and just subtract it from the current reading?

astrouga
 
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Re: Pyportal temperature inaccurate

by siddacious on Wed Jul 01, 2020 1:42 pm

Unfortunately until someone invents wireless wires, this is the best we can do!

These sensors are most often used to measure the temp of their immediate environment so using them to measure the room they're in is a bit "off label" but should absolutely work well if you keep the offset in mind.

You're right on the money about how to address this; to get the best measurement of the room by the PyPortal I suggest that you put the PyPortal in whatever environment/case/mounting that you intend to use it in. Then take a few measurements of the room with a different thermometer (not a remote one like for your central air) as well as with the PyPortal. Then find the difference between the PyPortal and thermometer's readings for each time you measured and average the differences to find the offset to use.

Once you account for the offset by subtracting it from the raw measurements like you suggested, I think you should get pretty accurate readings.

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Re: Pyportal temperature inaccurate

by kevinjwalters on Fri Jul 24, 2020 11:34 am

I have an 8833 infrared sensor attached to my PyPortal at the moment. My desk temperature is 27.6 and if I point the 8833 at the board it's reading about 36 degrees.

Are there any plans to do a STEMMA version of something like the 10K Precision Epoxy Thermistor - 3950 NTC? That would get the sensor away from the pcb.

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