This repository contains data and plots of a large scale non-scientifc comparison test of various temperature/humidity sensors.
Eight different sensors with a total of 21 units were tested simultaniously using two Raspberry Pi Picos (see Pico-Datalogger).
Besides normal indoor measurements there were two special phases: one period within a refrigerator and one within an oven.
Raw and processed data is within the data-directory.
Besides raw and clean data, there is also a calculated "difference from mean". Since the setup did not include a high precision reference, this mean is likely to be the most exact measurement.
Various plots are within the plots-directory. These plots were generated
using https://github.com/bablokb/py-datamon which is based on Pandas
and Matplotlib. Configuration-files for the plots are within the
config-directory.
Matplotlib allows to zoom into the plots, so for a detailed view of the data it is recommended to install "py-datamon" and run e.g.
py-datamon -c configs/bme280-absolute.json data/sensor-test1-combined.csv
The test did not bring up any unexpected results. All sensors are within the specifications as claimed by their datasheets.
Looking at difference to mean, the cheapest sensor (DS18B20) did the best job. The main drawback of the DS18B20 is that it only measures temperature.
Some sensors seem to underestimate (e.g. AHT20, BME280), some seem to overestimate (e.g. HTU31D). But this is not systematic and not alway true for all specimen of a sensor, so this should not be seen as a property of the sensor, but as an artifact of the given measurement series.
All in all, the measurement setup will have a higher influence on the measured values than the choice of the sensor.
Some Recommendations:
- Separate sensors from sources that influence the measurements. This implies /not/ to use a Pi or even worse a sensor Pi-hat.
- Shutdown the MCU or at least use deep-sleep modes inbetween measurements to minimize heat-creap.
- Check the sensor-initialization. Some drivers don't use ideal setups. The BMx280 is a very good example. The datasheet gives advice on how to initialize the sensor but some drivers/docs don't make it transparent on what they do. The Arduino-driver for the BME280 is perfect in this regard. The driver even provides presets to easily switch between settings.
The breakout-holder in the 3D-directory is licensed under:
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
