As you can see from the Chinese advertisements below it is possible to
source mounted BMP280 devices, small 50mBar air pumps, and 3.3V ESP32
microcontrollers with small display and WiFi/Bluetooth interfacing
in small quantities for less than £10 (~€12) altogether. I am studying
the possibility of using two pressure sensors in a differential mode
to measure the pressure difference between local atmospheric and the
pressure needed to blow bubbles at the bottom of a grey water store
in order to measure the current water depth. Both sensors will, of
course, remain in dry air.
Staying within the published parameters of the BMP280 allows us to
measure depths to about one metre. If we were to use the BMP390 and
stay within its published parameters we could achieve 2.5 metres,
but Chinese BMP390 boards are about ten times the price of the
BMP280 ones. We therefore intend to experiment with the BMP280 at
depths of up to 2.5m.
I suspect that both devices would work with reduced accuracy to
somewhat higher pressures. We do not need the 5mm water accuracy
of 0.5hPa - 1 cm (or probably 1 inch ~2.5cm) is more than adequate
for shallower tanks, and the deeper tanks (<=5m / 15 feet) probably
need no better than ±5cm (2 inch or about ±5hPa) accuracy.
We could buy a handful of devices and measure them for ourselves
(and it would be a useful student exercise) but as all the devices
might be from a single batch this does not give us a useful figure
for predicting achievable performance with OTS devices.
I am therefore writing to enquire if anyone has experience
of the performance of the BMP280 and BMP390 up to 1,500 hPa. I do
appreciate that such an estimate is in no way binding on Bosch
(especially as many of the devices used will be sourced cheaply
on the surplus market) but it would help greatly in designing
a suitable project.
https://www.aliexpress.com/item/1005006989754536.html
https://www.aliexpress.com/item/1005003795946661.html
https://www.aliexpress.com/item/32842966602.html