Olen hetken aikaa ihmetellyt sisätiloissa olevan kahden Ruuvi Tagin ilmanpainemittauksen eroa. Ero on n. 0,3 - 0,4hPa. Mutta sitten välähti! Nehän ovat eri kerroksissa. Ilmanpaine maanpinnan tasolla muuttuu n. 1hPa / 8m. Näin ollen nuohan näyttävät ihan samaa. Korkeusero on hyvinkin (mittaustarkkuuden rajoissa) tuon n. 2,5 - 3,5m. Tarkkoja ovat…
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V12 says:
I’ve been wondering for a while about the difference between the two indoor Ruuvi Tag barometric pressure measurements. The difference is approx. 0.3 - 0.4 hPa. But then flashed! They are on different floors. Air pressure at ground level changes approx. 1hPa / 8m. Therefore, they look exactly the same. The difference in height is (within the limits of measurement accuracy) about 2.5 - 3.5 m. The exact ones are…
I have 4 Ruuvi sensors. The sensors have the latest firmware (updated with the Anroid Ruuvi Station app).
Each of the if sensors has a new battery, but some of the sensors are old (5+ years) except for 08D0, purchased a couple of weeks ago.
I implemented a Windows SW to listen for BT Advertisement messages. It plots the readings from the sensors.
The sensors are located in a sealed plastic box. When reading the sensor data, the pressure vary a lot. When all sensor are in same location, there should not be this kind of variation.
My intention is to implement a SW where I can compare indoor/outdoor pressures and pressure changes in a home ventilation unit. By accessing the measurements, I would then be able to adjust the unit.
Is there anything I can do? Or is this normal behavior of the sensor, it can’t do any better.
The ±2 Pa (±0,02 hPa) noise we can see in the graphs looks normal.
Older RuuviTags have Bosch BME280 pressure sensor and the latest ones have Infineon DPS310. Here you can find their datasheets:
bst-bme280-ds002.pdf (1.6 MB)
Infineon-DPS310-DataSheet-v01_02-EN.pdf (749.2 KB)
The noise you asked about is not probably the biggest problem you would need to worry about when trying to sense pressure differences in your ventilation but drifting in different temperatures may be. I personally haven’t tried to use RuuviTags to do this but @ojousima told that he did try and the problem was that when temperature changed outside (but not inside) of the house, the pressure sensor readings started to drift. But maybe if you can control the temperatures, drifting will not be such a major issue.
But depending on your requirements, it is highly possible that RuuviTags are not accurate enough for this use.
ilhe: The graph you have shown only varies 0.1 hPa.
Try drawing the graph at a different baseline and scale.
As with many graphs the baseline can exaggerate or minimize the variation.
I use inHg causes the graph to baseline at 28.5 top of y axis is 30.5. .5 inHg per y axis lines and the graph always looks very smooth.
Lauri: perhaps having the app “round down” the minimum and “round up” the maximum would minimize the variation not only from tag to tag but also over time.
See the graphs at https://mybeacons.info/pressure_inVSmm.html
same data same time period.
in inHg looks smooth but in mmHg looks very variable.