BME280 Pressure, Temperature and Humitity Sensor

[RGV250]

Hi Craig,
I cannot help with the BME280 but I have several SHT31 Smartgadgets https://uk.rs-online.com/web/p/sensor-development-tools/1237130 and the temperature is pretty much the same on all 3 but the humidity can be out by a couple of % when they are next to each other. Not the discrepancy you are seeing but still out. If I recall the humidty accuracy is within +/-2%

Bob

[trastikata]

Bosch sensor should be accurate according to its data sheet.

You are mixing relative (reaction to T change) and absolute (compared to actual T) accuracy. The temperature sensor has about 3 degrees (+-1.5*C) absolute accuracy according the datasheet. Also keep in mind that if it is on the same board with regulators or MCUs they will rise the die temperature.

About the RH - 40% sounds much more realistic than 23% unless it's -20 outside and the heating is working. Otherwise at this time of the year, without special de-humidification system in the box, I doubt the actual RH could be 23%.

[Craig]

Thanks Trastikata

The sensor is on a 1/2m cable from the PCb into the enclosure so it should only pick up the temperature / Humidity in the enclosure.
The Temperature variance will be too much as you have pointed out. We are in South Africa at the end of a very Dry Winter so the RH is about 20% outside currently but, I was just using the Values as an example. I will I will put the DS18B20 in for now and have to look for a more accurate Temperature sensor so I am open to any suggestions? Thanks for the help.
Regards
Craig     

[Craig]

Thanks very much Bob only saw your post now, that is a very nice unit and will be good for testing. The humidity I can live with but, the temperature must be accurate.
Regards
Craig

[trastikata]

I will I will put the DS18B20 in for now and have to look for a more accurate Temperature sensor so I am open to any suggestions?   

I doubt you can find a sensor with that high absolute accuracy, I'd rather go with a normal sensor and some calibration process.  Check out this article:

https://www.kandrsmith.org/RJS/Misc/Hygrometers/absolutetemperature.html

[Craig]

Thank you Trastikata

It is a very interesting article and thanks for your valuable input I appreciate it.
Regards
Craig

[RGV250]

Hi Craig,
They also do a newer one but I have not seen it for sale yet, I would hope the 43 is more accurate than the 31 but who knows.
https://sensirion.com/products/catalog/SHT43-DemoBoard

Bob

[Craig]

Hi Bob
Thanks I see there is even a SHT45 Which looks very impressive but, I don't know if this is available in a demo board yet.