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Rough environment rotation speed sensor

Former Member

Hello altogether,

 

I want to measure the rotation speed of a auxiliary fan which is enclosed in a duct pipe system.

There will be humidity and steam from boiling water (can compare to cooking on a gas hob in the kitchen)

 

The fan blades are made of plastic.

 

I was recommended to use an optical sensor, but I am worried that the steam will interfere.

 

Has anybody experience with something like this and can recommend a certain type of sensor or maybe even a special product?

 

Thanks guys!

Parents

  • Thanks to all of you for the feedback.

     

    I have a device called "Duct Blaster" http://products.energyconservatory.com/minneapolis-duct-blaster-system/

     

    It is used to measure pressure/airflow within a system. (They sell for determination of leakage in housing ventilation systems)

     

    Their meters are set to standard ambient conditions 20ºC, 1013.25hPa

    As I use the Duct blaster to measure the air movement of a hot airflow, the density will change. Hence I need to work out a corrective factor for the indicated airflow.

     

    It is quite easy for the temperature and the barometric pressure, but the steam (vapor and condensate) will effect the density as well.

     

    By knowing the rotation speed of the blades, I can calculate the real airflow without any corrective factors.

    (N1/N2) = (D1/D2)-3 (Q1/Q2)

    D = Fan size

    N = Rotational speed

    P = Pressure

    Q = Volume flow rate 

  • in reply to Former Member

    Have you considered using a small microphone and using the sound to determine fan speed?

     

    You should get a measurable difference when the fan blade passes by the mic, which would allow you to directly measure the fan speed.

     

    DAB

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