mass liquid flow meter?

[[email protected]]

Anyone know of a circuit to measure flow using two thermistors? I.e.
it determines how much flow there is by measuring how much power it
takes to maintain one of the thermistors at a certain temperature?

Why do you need two thermistors anyway? Cant you just figure out how
much power it takes to keep one thermistor at a certain temperature?

 

[Phil Allison]

Anyone know of a circuit to measure flow using two thermistors? I.e.
it determines how much flow there is by measuring how much power it
takes to maintain one of the thermistors at a certain temperature?

Why do you need two thermistors anyway? Cant you just figure out how
much power it takes to keep one thermistor at a certain temperature?

** The second thermistor might be needed to determine the temp of the
liquid, so that can be eliminated from the computation of flow rate.



....... Phil

 

[Tim Wescott]

** The second thermistor might be needed to determine the temp of the
liquid, so that can be eliminated from the computation of flow rate.

Yup. I've been thinking of building one of these -- they're used in
sailplanes (both model and full size) to measure the flow of air into a
bottle as a hyper-sensitive rate of climb indicator. Apparently you put
them in a bridge configuration and the merest whisp of air flowing by will
unbalance the bridge enough for a useful reading.

Dunno any more, though -- I'm going by memory of an article I read 30
years back.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[Paul Hovnanian P.E.]

Yup. I've been thinking of building one of these -- they're used in
sailplanes (both model and full size) to measure the flow of air into a
bottle as a hyper-sensitive rate of climb indicator. Apparently you put
them in a bridge configuration and the merest whisp of air flowing by will
unbalance the bridge enough for a useful reading.

Dunno any more, though -- I'm going by memory of an article I read 30
years back.

Google 'Mass Air Flow sensor'. They are used for lots of stuff,
including inputs for fuel injection on most cars.

 

[Jim Thompson]

Anyone know of a circuit to measure flow using two thermistors? I.e.
it determines how much flow there is by measuring how much power it
takes to maintain one of the thermistors at a certain temperature?

Why do you need two thermistors anyway? Cant you just figure out how
much power it takes to keep one thermistor at a certain temperature?

Sure. Check out by BSEE Thesis, "Blood Flow Rate Using Thermistors",
James E. Thompson, MIT, June 1962.

...Jim Thompson

 

[ehsjr]

Sure. Check out by BSEE Thesis, "Blood Flow Rate Using Thermistors",
James E. Thompson, MIT, June 1962.

...Jim Thompson

I got:
Your search - "Blood Flow Rate Using Thermistors" - did not match any
documents.

Can you post it? I know, I know, probably gone
after all these years, but worth asking for on
the chance you still have it.

Ed

 

[Adrian Jansen]

Yup. I've been thinking of building one of these -- they're used in
sailplanes (both model and full size) to measure the flow of air into a
bottle as a hyper-sensitive rate of climb indicator. Apparently you put
them in a bridge configuration and the merest whisp of air flowing by will
unbalance the bridge enough for a useful reading.

Dunno any more, though -- I'm going by memory of an article I read 30
years back.

Thermistor based varios - climb rate meters for sailplanes - were
superseded by pressure transducer versions about 30 years ago. Much
more stable, easier to calibrate, and simpler.

Thermistor flow rate meters are only useful over relatively small flow
ranges, and for certain fluids.


--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
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