On-Line Sensors for Measuring Gas Flow

Any positive displacement flowmeter will do this task.

If the pressure and temperature is variable, then NO!

if the pressure is fixed then a positive displacement (volume measuring) flow meter may be able to be used...

Trouble is most volume measuring flowmeters are also sensitive to humidity and viscosity of the gases measured, so there is no easy answer.

John.

Universal Gas law says:

PV=nRT

Pressure, temperature compensated Vortex Flowmeter may be the best solution.

See www.krohne.de or www.forbesmarshall.com

Mass flow meter like micromotion or E&H which only depend on the coriolis effect can measure the mass flow without being affected by composition ,pressure ETC.

I've generally had good luck with FCI's thermal mass flowmeters www.fluidcomponents.com. They generally work best with gasses around room temperature and can be set up at the factory with preprogrammed spline curves if you know the general composition. Yes, it may be a variable composition, but you should at least know something about what you are measuring. Otherwise why are you measuring it in the first place? I do like vortex meters, but they tend to get very expensive above 2" or so. Thermal mass meters can be insertion mounted making them more economical for large pipe sizes.

Eny Wet/Wet Diffrential pressure sensor, 16 bit A/D comnverter and microcontroller with 2 X16 bit timer/counter ( PIC18FXXXX ) can do this job.

Any wet/wet diff pressure sensor.....

Huh!!? what's a pressure sensor going to do measuring flow rate??

I think you have missed the point that the questioner is measuring flow not pressure.

John.

Mount the diffrential pressure sensor on Pipe that have orifice plate in. (An orifice plate is basically a thin plate with a hole in the middle. It is usually placed in a pipe in which fluid or Gas flows.)

.

Nope, that won't do either...

An orifice plate's calibration depends on the gas properties, pressure as well as temperature.

John.

Yes, of dont know density of gas then add one temp sensors inside pipe and write a lookup table in microcontroller according to temp.

All is doing that ways. i also doing.....

1 - calibrate flow at 20°

2 - up temp of cylender at 50° and find diffrence then lookup table for cpmpensation.

Take atleast 20 temp point at 5° diffrence for lookup table.

You will reduce non-linearity according to temp.

Sorry but you are talking rubbish, if the gas's composition is changing then your look up table will have to vary as it changes.... it will also have to vary with temperature and pressure as well...

How will you measure the gas's composition?

alicat scientific flow sensor

Hello Sir Electroman, ( You'r kicking me intyo my past )

I know gas and liquid flow can be measured in volumetric or mass flow rates. These measurements can be converted between one another if the materials density is known. I also know the volumetric gas flow rate will differ for the same mass flow rate when at differing temperatures and pressures.

I also know, buddybaxter don't wants to measure flow of Standard Dry Air, where the humidity and the temperature will determine the amount of water vapour that can be present in gas.

But buddybaxter wants to measure the flow of gasses whose composition is variable and unknown. In this case CONDITIONNING of gas is neccesory. becouse he try to Monitoring Real time flow of Air Pollution (car traffic, domestic heating, industrial activities or transported by the atmospheric circulation eg. duct etc.)

But my microcontroller's programming, temp sensor, diff. pressure sensor, Humidity sensor, and lasser diode ( diode emitting energy and detect by the infrared spectrum) and my lookup table and ref. table is sufficient for flow measurements and i selling in India. But This Units are not recommended for gasses with a molecular weight less than 16.

Thanks

Precision,

This setup is beginning to sound like the recipe for rock soup. Your original reply only says you need a DP sensor and a microcontroller. The next one only adds an orifice plate. Then you add temperature, humidity and a laser diode to the system. The original poster wants an industrial instrument only to measure mass flow. How do you calibrate and certify the setup you suggest? How does an instrument tech verify and troubleshoot it if an engineer is not available? You are also assuming the the original poster wants to measure air pollution. Where was this stated in the original post? Even if this is true, air pollution would only be a tiny percentage of standard air and mass could be accurately measured with a standard thermal mass flow meter. He's not asking for lab grade readings.