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flow / velovity measurement

flow / velovity measurement

flow / velovity measurement

We are trying to get away from discrete alarming on Exhaust flow.  We have considered a number of options with analog transmitters, but I thought that I would through the this out there to see if anyone had any ideas / reccomendations.

the 2 meters I am presently looking at most are Dwyer:


as well as one from E+E Eleoctronics

RE: flow / velovity measurement

Oh yeah, some of the applications are somewhat dirty, and acidic

RE: flow / velovity measurement

What is the purpose of getting away from discreet alarming? If you use an analog signal you will still have to set a limit at which the airflow is unacceptable. Unless you need a specific airflow reading at your monitoring station?? If this is the case, I would choose the 4-20ma output instrument, especially if the distance is long between the instrument and the analog input card.

RE: flow / velovity measurement

yes, the Dwyer are 4-20, but they are 3/4 wire, and we want 2 wire.  

We are a heavily regulated facility, and it has been stated that more precice SPs are required, and that exhausts will eventuall be mandated to have totalisers.  

RE: flow / velovity measurement

Review the exhaust conditions i.e. temperature, pressure and chemical composition. As with most regulated process you need to report SCFM * time to get to total CFM. The Dwyer probe you are looking at is for clean dry air at atmosphic pressure and is a single point in the air stream.  I recommend the use of a permanent flow monitor flow grid in the exhaust duct. I have used


You can get custom sizes. You need to determine the system accuracy and do a very good initial calibration that is traceable.

Take the delta p output to a transmitter with 4-20ma or 0-10v output. Various mfgs offer complete solutions with local display. It sounds like you are trying to reuse the existing 2 wire alarm system. If the wiring is your problem, you may want to look into a wireless solution.



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