I'm in the middle of building a small ESP32 controlled pump to inflate an object. The object under pressure is in the range of 0-10psi. I needed a "small" pressure sensor that I could read directly from I2C and be relatively inexpensive. There were a few options.
Adafruit MPRLS Ported Pressure Sensor Breakout - 0 to 25 PSI for $15.
Various HX710B based sensors for around $3 on Ebay but only 0-40KPa (0-5.8psi).
Various raw high pressure sensors with 1/4 inch mounts but to BIG!
Then I looked up the data sheet for the BMP180. It lists a pressure range from 300-1100hPa (4.3-15.9psi). Do you think this sensor will give accurate reads in the low pressure values?
So decided to modify a typical $5 BMP180 by epoxying an 1/8 brass tubing directly to the sensor top. To get a usable sensor I take the raw reading while at zero pressure (which is some number in the high thousands) and subtract it from itself to get a zero level.
So far this seems to be working. I haven't checked to see if the values are accurate with a different type of sensor but in the device the values seem reliable(repeatable). The duty cycle is very low for the application(few times per hour up to 10psi max). Any reason why I shouldn't be using this sensor in this way? Will it survive this application?
The BMP180 is an absolute pressure sensor and will be destroyed if subjected to significant overpressure. Others are called "gauge" or "gage" and measure relative to current atmospheric pressure.
Only through experimentation, when using the sensor outside of the manufactures operating parameters, like gluing a tube over the sensor, would you be able to find out. Try it and let us know. I'm very interested in your outcomes and if the idea passes a 100 hour test.
I'm very interested if outside tube pressure affects tube pressure. Such as run the tube through a plastic bottle, seal the tubes entry exit points, cap the bottle and squeeze, does the pressure readouts change, by how much? If the tube is made more rigid does the bottle squeeze effect the pressure reading?
Go on, experiment.
Then there's the Adafruit MPRLS Ported Pressure Sensor Breakout - 0 to 25 PSI or the MPXV7002DP Transducer APM2.5 APM2.52 Differential Pressure Sensor but, of course you knew about this already from the research you've done.
Nifty idea but the data sheet I downloaded show a range up to just over 15psi. (maybe I missed the 145psi bit)
Anyhow, there is also the external pressure supply to consider i.e. pulses from the compressor if that is what is used.
A regulator may help but may not be fast enough.
The data sheet says that the pressure measurement range is from 300 to 1100 HPa.
The algorithm to calculate pressure and temperature in the sensor is complex, and the readings will probably become meaningless for pressure far outside that range.
JCA34F:
That's the pressure the package can withstand before it explodes and blows your eyebrows off. I wouldn't recommend trying it!
Ah I see. Well for this application it should never go above 10psi.
jremington:
The data sheet says that the pressure measurement range is from 300 to 1100 HPa.
The algorithm to calculate pressure and temperature in the sensor is complex, and the readings will probably become meaningless for pressure far outside that range.
I'm taking the raw sensor reading and should stay within the 10psi range.
bluejets:
Nifty idea but the data sheet I downloaded show a range up to just over 15psi. (maybe I missed the 145psi bit)
Anyhow, there is also the external pressure supply to consider i.e. pulses from the compressor if that is what is used.
A regulator may help but may not be fast enough.
jremington:
Do you not understand that a ball, pumped up to "10 PSI", has absolute internal pressure of about 25.7 PSI, 10 PSI above atmospheric pressure?
Oh.. I wasn't sure what you were getting as. I understand now. So I'm really reading 10psi above atmospheric.
I guess I'll use it for a while and see what happens.
