This could be bad...

A project log for VISP - Ventilator Inline Sensor Package

Bidirectional flow (volume), pressure, and temperature sensing in a single inexpensive I2C/SPI package.

Daren SchwenkeDaren Schwenke 04/04/2020 at 06:111 Comment

@djeddleman had two BMP180 development boards in his stash of stuff.  He was kind enough to hook them up to one of the older generation pitot tubes we designed that used tubes still, and take some measurements.  

The results were far less than promising.

We saw basically no deviation in the pressure differential read by the two sensors at flow rates of up to 3m/sec, and a static offset greater than that 'signal' by like 5 meters of an air column.  That is outside the spec for even these.  The new sensors are an order of magnitude more sensitive, but 10x nothing is still nothing.

I can only hope that perhaps one or both of the sensors was plugged or damaged during testing at this point.  There was RTV involved, so it is a possibility and would explain the static offset.

@Steven.Carr plans on attempting to etch a board tomorrow to try the same test with our BMP388 boards, and hopefully have better results.  The pads are truly tiny though for these devices, so... wish him luck.


Bharbour wrote 04/04/2020 at 12:41 point

Not sure if it is relevant or not, but in the past, I saw extremely stringent requirements for what the humidity sensor from another vendor could be exposed to without damage. I looked in the Bosch data sheets and did not see anything like this mentioned. Unfortunately, I don't remember who the other vendor was (a while ago and not that useful information at the time). At any rate, it might be worth contacting Bosch to see if their sensors have any particular sensitivities.

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