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
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
Google 'Mass Air Flow sensor'. They are used for lots of stuff, including inputs for fuel injection on most cars.
-- Paul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ Stop Continental Drift! Re-unite Gondwanaland!
Sure. Check out by BSEE Thesis, "Blood Flow Rate Using Thermistors", James E. Thompson, MIT, June 1962.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
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
Thermistor based varios - climb rate meters for sailplanes - were superseded by pressure transducer versions about 30 years ago.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 Note reply address is invalid, convert address above to machine form.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.