Hi,
I have a system where I want to measure the oxygen flow.
The flow may vary but has a maximum of about 50 Liters per minute.
The sensor should not be an additional resistor to the gas flow.
Can anyone recommand an inexpensive sensor?
Kr and thanks,
Andreas
Define "inexpensive"! For such sensors I would define it as "below $200" but your definition may be different.
Andreas1984:
The sensor should not be an additional resistor to the gas flow.
The least effect on the flow is probably when you use an ultrasound type flow sensor, but the cheaper (mechanical) options all will affect the flow.
Oxygen is a tricky one , from a safety and material point of view .
I doubt you will get anything especially cheap , but google shows several devices.
One possibility is to put a fixed gas frit/restrictor inline with the flow and then attach a differential pressure transducer across it and have an absolute pressure transducer at one side of the frit/restrictor.
There are equations that relate mass flow rate to the readings on these two sensors. The Freescale transducers are a reasonable price for this.
This is a technique used a lot on various instrumentation.
Temperature can affect results though so that needs to be compensated for or controlled.
Sorry - just saw note on no restriction. You might get away with a low restrictor?
How about a hot filament/thermister device? They work well for air and nitrogen. Might cost a bit more than you want. They have insignificant effect on pressure.
Try Sensirion, they were offering low cost flow sensors at one point:
Wombat37:
Sorry - just saw note on no restriction. You might get away with a low restrictor?How about a hot filament/thermister device? They work well for air and nitrogen.
It seems you also missed the "oxygen" part. Or you don't understand what that requirement means for sensors.