Detecting air flow

[benjus]

Hi all,

I'm new to these forums... I have some knowledge and experience with electronics but I'm no expert.

I'm interested in working on a project which would involve measuring the air flow through a pipe. The air could flow in both directions and could change direction suddenly - the sensor would need to report both the speed (or the pressure) and the direction. The speeds and pressures involved would be low and the readings would be ultimately be sent to a PC, so I'd prefer to use 5V components (although 12V would be acceptable).

The main consideration is that it should be very responsive - especially when a change of direction occurs. I would like to get a response in the order of 100 milliseconds rather than seconds. Accuracy of the speed measurement is not critical.

I don't really know what kind of sensor I should be looking at for these requirements, so I'd welcome any suggestions. Of course, it may be difficult to accomplish all this with a single sensor, so I could perhaps use two sensors with non-return air valves to cover both directions.

Thanks for any ideas!

[DerFly]

Hello my friend,

Do a net search on "air mass sensor" and "hot wire" as used for automotive engine management sensors.

This should give you a few ideas to research.

DF

[Hero999]

There are plenty of ways to do this, hot wire is probably the best but needs to be compensated to the ambient temperature.

[Herman the German]

Hi,

you might want to try out this circuit. It uses transistors to sense airflow and its output is PWM.

If you want to obtain the Eagle files please PM me leaving your email address.

HtG