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Topic: Sensor accuracy (Read 973 times) previous topic - next topic

song85129

Hi guys, I just tried my nano 33 sense board with temperature and humidity readings.
However, the temperature is about 5 degrees higher and humidity is about 10% lower than my other off the shelf temperature and humidity IoT devices.
Would that be normal? I know I can add an offset in the code to make it to the same level but I thought those sensors should be able to be reasonably accurate.

Just wondering if any of you have similar issues.


carpetafhf

Hi!

I have the same problem, temperature 5 degrees higher, and in my case humidity is 8% higher. I'm comparing the result with an Oregon station. I'm always having problems related with precission in temperature sensors (DHT22, BME280....) and I tought that with the integrated sensors in this Arduino my problems went out, but no :(

I'm using the example code name "ReadSensor", so the code is supposed to be ok. Any ideas?

Thanks!

ballscrewbob

#2
Nov 15, 2019, 01:11 am Last Edit: Nov 15, 2019, 01:11 am by ballscrewbob
It is not unusual to have small variations in sensor readings.
Even an oregon weather unit will have some variation.

Best it to take an average set of reading to get a closer figure and then either use them or add / remove an OFFSET value.

Bob.

It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

carpetafhf

Hi!

First of all, thanks for your answer. I know that small variations are normal behaviour, but 5 celsius degrees compared with another units (I posted the oregon example, but it matches with the home thermostat and another external thermometer) is too much, since the accuracy is supposed to be 0.5 degrees, so the error is unacceptable.

Does exist a calibration process ?

thanks

ballscrewbob

If you have the Chinese variations of these sensors it would be a normal variation as they do not choose the best components to match the specifications of sensors for many of the modules.

As explained usually an OFFSET / or running average is the best approach especially for the DHT sensors.

I don't believe there is a calibration method apart from checking the components on any module board and swapping them for the manufacturer's recommended whilst reading the application notes.

Also be aware that close ambient temperature can throw readings out wildly.
A good approach to that is yo use a shielded cable of suitable length to move the sensors away from such sources.

Bob.




It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

carpetafhf

Hi,

I wrote the examples with another sensors because I always haver precission problems, but in this case I'm using the integrated sensor in the Nano 33 BLE Sense, so there are no chinese sensors, cables...nothing. The HTS221 specs are very clear: 0.5 ºC between 15 and 40 ºC, so it's very dissapointing to get an 5 ºC error.

More ideas?

Thanks!

cson003

Hi,

I wrote the examples with another sensors because I always haver precission problems, but in this case I'm using the integrated sensor in the Nano 33 BLE Sense, so there are no chinese sensors, cables...nothing. The HTS221 specs are very clear: 0.5 ºC between 15 and 40 ºC, so it's very dissapointing to get an 5 ºC error.

More ideas?

Thanks!
Hi, sorry I forgot this thread.
It is sort of relief to see I'm not alone.
I agree with you the sensor reading on this board are way out of their designed tolerance. Therefore, they are faulty in my eyes. This can not be blamed to Chinese sensors. No matter what kind of component they use, if the output is out of their specification, their product is faulty.

I contacted Arduino store support two month ago and they told me their developer were testing it.
I asked again last month and they were still testing.
I just send another email asking what is going on and asking for a refund.

Really disappointing.

cson003

If you have the Chinese variations of these sensors it would be a normal variation as they do not choose the best components to match the specifications of sensors for many of the modules.

As explained usually an OFFSET / or running average is the best approach especially for the DHT sensors.

I don't believe there is a calibration method apart from checking the components on any module board and swapping them for the manufacturer's recommended whilst reading the application notes.

Also be aware that close ambient temperature can throw readings out wildly.
A good approach to that is yo use a shielded cable of suitable length to move the sensors away from such sources.

Bob.





Hi Bob, thanks for the reply.
The problem is that none of the sensor reading make sense and the variation is not small.
If they specify the sensor tolerance to be +-5, then, a 5 degree difference to the actual reading is acceptable to me as that is as expected.
However, a 5 degree difference in temperature or 30% difference in humidity are way out of their designed tolerance. Therefore, they are faulty parts.




jojobaa

Hi, we have updated the getting started page of the BLE sense with regards to the accuracy of the sensors. Please read the section under "Relative humidity and temperature on the Arduino NANO 33 BLE Sense".

Getting started: https://www.arduino.cc/en/Guide/NANO33BLESense

cson003

Hi, we have updated the getting started page of the BLE sense with regards to the accuracy of the sensors. Please read the section under "Relative humidity and temperature on the Arduino NANO 33 BLE Sense".

Getting started: https://www.arduino.cc/en/Guide/NANO33BLESense
Hi, Could you check the email I sent you please?
The solution you suggested could not fit my purpose and therefore, I'm asking for refund please.
Please let me know where I should post the board to.

Thank you.

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