Hello,
I have a BMP280 pressure sensor, which I use to measure Baro, and I getting familiar with it. I am now doing a project driving some fans with DC motors, and was wondering if there might be a way to use the BMP280 to measure static pressure and status pressure drop in a duct. Can anyone have direct experience with the BMP280 pressure sensor in an airflow measurement application? Thanks. Steven Lightfoot
Have a google of Bernoulli and how to calculate the various pressures , then you can see whether your 280 is upto the job .
Thanks. I am pretty familiar with fluid flow, and the sensitivity of the BMP280 is probably good enough simply for a static pressure reading below baro, assuming you can install it into the right place and/or tube it or install it properly into a duct port, and prevent local leakage. My question is more: is anyone doing this now?, with any actual projects, or direct practical experience that I might be able to learn from, to speed my project development. I realize the BMP280 is only abs pressure, it is a DP transducer. I appreciate to your comment.
You can do the sums to see if it is sensitive enough . There is loads on the internet about how to measure flow in ducts or pipes using pitot meter for example .
Cool thanks. Yes I saw some stuff. I want to see if I can simply use a static port, calibrated, using a flow meter to calibrate it prior. I am characterizing the BMP280 at the moment, testing sensitivity and noise levels. I will come back with some info.
You will struggle with a fixed port - if there is a downstream restriction for example the flow will reduce and the pressure rise - you need an orifice plate or a pitot tube .
Note to that as there is a square root relationship between flow and pressure drop, you will only get any sensible output over around a 3 to 1 flow range .
Have a good look at flow measurement - the pressure you will read at the pipe is comprised the static and dynamic pressure.
Your measurement needs to be away from bends too - say 10xdia of pipe up and downstream
Love your comments thanks, very useful. I have a background in aerospace engineering, test engineering etc I did tons of this kind of stuff 25 years ago, but have forgotten a lot of the details, so need to relearn. I discovered Arduino a year ago, and am blown away by what you can now do at home. My actual goal. really just noodling around, is to set up a blower with a variable speed control and get some feedback, to be able to develop a PID to control it and play with the PID tuning. So I just need some kind of feedback, and was thinking I could simply use a static port, if the BMP280 was sensitive enough (which I am still trying to figure out). I will definitely comeback to you with some results when I have them. Steven Lightfoot
I have now done more research, and can conclude this: The BMP280 will operate to a slight overpressure from baro and down to as low as 300 hPa. Its stated relative accuracy is +/- 12 Pa. My measurements to date of Baro over time seem to indicate its noise level is about +/- 4 Pa. Its reading resolution is 1 Pa. One inch water is about 250 Pa so this thing really is extremely sensitive. I am now very confident that I can use it for what I want, but as you state above I will have to design whatever I end up using in such a way that the static port doesn't measure an INCREASE in the backpressure in the flow line, which is what it would nominally do. I will continue my work and report back when I have some idea where I am taking this. Steven Lightfoot
Now what I have done is set up a simple rig with a cold air blow drier blowing normal to the tiny hole opening of the BMP280, and record running snap data every 500 mS. The results are shown below. Its very clear the BMP280 is picking up the increase in total pressure directed at it, in the order of about 100 Pa. So basically I have what I want, confirmation that this BMP280 transducer will pick up the level of pressure changes I need. Now I have to figure out what kind of setup I want. This is going to take a long time, but I will report back. All you comments were helpful, all my aero engine fluid flow knowledge is flooding back. Steven Lightfoot
And I agree that if I want to use a static port only, I will need to built a venturi system, or something, and measure at the throat.. Steven Lightfoot
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