design an electronic gas flow and pressure meter

[djomgoue]

Here are the specification:

Pressure
Operating pressure (Differential): - 200 to 200 mbar

Flow
Operating Flow Range: 0 to 100 l/min

Oxygen measurement
Range : 0 to 100%

Gas temperature
Range:0 to 50 °C

can somebody put me on the right direction please...

Regards

 

[FvM]

The specification should be supplemented by accuracy requirements. How about pressure correction of concentration and flow measurements? Is the flow measurement expected to be true volumetric (media independent) or is calibration for pure O2 sufficient?

Regarding O2 sensors, does an electrochemical sensor meet your requirements https://www.figarosensor.com/products/O2.pdf or do you require an expensive paramagnetic instrument?

Figaro’s products are not authorized for use as critical components in life support applications wherein a failure or malfunction of the products may result in injury or threat to life.

 

[djomgoue]

hi, thank you for you reply.
In fact this is what i want to build a device that will be able to measure the flow of medical case in a patient tube before it get to the patient so in addition to that i want to measure the flow and the oxigen concentration in that gas before the patient inhale it.
In fact i am looking for circuit diagrams and technology (sensor) use to capture those information.

here are more specification as you asked:
Pressure
Operating pressure (Differential): - 200 to 200 mbar
Span accuracy: ± 0.75 % or ± 0.1 mbar

Flow
Operating Flow Range: 0 to 100 l/min
Accuracy: ± 1.9 % or ± 0.1 l/min

Oxygen measurement
Range : 0 to 100%
Accuracy: ± 1 % O2

Gas temperature
Range:0 to 50 °C
Accuracy: ± 1.75 % or ± 50 °C

Hoping it help you to help me.
thank you.

 

[FvM]

Particularly the flow meter specification is rather challenging and easily to achieve.Would you allow a pressure drop by the meter, e.g. if it's mounted in the pressurized supply line?

 

[djomgoue]

Particularly the flow meter specification is rather challenging and easily to achieve.Would you allow a pressure drop by the meter, e.g. if it's mounted in the pressurized supply line?

Yes pressUre drop its not A problem.
Please give me something to start working On.
The air its sUpply from a bottle.

 

[FvM]

A thermal mass flow meter will roughly meet your specification, e.g. https://www.brooksinstrument.com/do...al Gas/Data Sheets/ds-tmf-sla5800-mfc-eng.pdf
The linked Bronkhorst SLA58xx have higher absolute error (0.2% of full scale range) than you specified. You'll find that these devices are quite expensive.

A more economic thermal mass flow meter with reduced accuracy is made by swiss company Sensirion https://www.sensirion.com/en/products/mass-flow-meters-for-gases/ It's also available from Farnell.

Unfortunately I don't know how to achieve the demanding specifications with less effort. I also presume that designing flow meters from the scratch will be beyond the reach of your project.

Thermal mass flow meters are also available with built-in flow control.

 

[djomgoue]

the point of the project its that i have to make those sensor myself.so i was expecting some circuit diagram on how to pic up a flow rate.
thanks for you help...

 

[FvM]

"Making the sensor yourself" is a problem of the sensor physics. There's no easy way to make a sensor with the intended accuracy. It's not so difficult to make a sensor with maybe 10 % relative accuracy using e.g. a venturi nozzle or hot wire respectively simple thermal mass flow measurement principles. E.g. using a sensor element like this https://uk.farnell.com/ist-innovati...flow-sensor-gas-100m-s/dp/1266952?Ntt=1266952

You still need some knowledge of physics and mechanical engineering to make a gas meter based on this sensors.

 

[djomgoue]

I just checked the flow sensor FS1 and i think its what I need with no doubt. Don't you have an application of it where it was use before?

Another problem can you recommend me a website where i can buy it? i am in South Africa and farnell.com doesn't have South Africa in the country list.

Please advise on what to do.

 

[FvM]

IST has a south african distributor, see https://www.ist-ag.com/ under contact

 

[djomgoue]

don't you have an example where someone use the sensor in an application.

 

[djomgoue]

hi,can you advise me on a oxygen sensor that is small as the FS1.can i measure the temperature of the air flowing using the FS1?
thank you

 

[FvM]

I presume, you'll need a separate unheated sensor for the temperature measurement. I'm not aware of a smaller oxygen sensor than Figaro KE-xx with similar performance and reliability.