A Sampling of Commercial Flow Meters

 

Here are a few commercial flow meters that are on the low end of the cost scale (but still not that cheap).

 

If you find something better, please let me know.

 

 

Venturi with Target
www.watermeters.com -- home of the dlj meter

www.watermeters.com 

 

 They sell a wide variety of water meters, including hot water meters, and meters that also output a pulse count for loggers.  As low as $45.

(thanks to Chuck for suggesting this)
Sources:

 

www.kingsolar.com
King Solar

www.Omega.com
Look for: FL45101, FL6300, FL46302

http://www.dwyer-inst.com
Look for Series UV, VFCII

 In these meters, the flow pushes a target up a tapered flow -- the greater the flow, the higher the target rises. Easy to read the flow at a glance.  Normally no electronic output.  Mount vertically.

Moderate pressure drop.  Some models can handle the full temperature and pressure range encountered in solar thermal projects.

$75 and up -- over $200 for full temperature and pressure capability.
Sources:

www.Omega.com
Look for FLMW, FLMH, FLMW201, ...

http://www.dwyer-inst.com
Look for series HF

 

 In these meters, the flow deflects a turbine or disk which is restrained by a spring.

High operating temperature and pressure capability.  Moderate to high internal pressure drop.   Mount in any orientation.

$65 and up
Paddle Wheel Meters

http://www.gemssensors.com/TOCproducts.asp
Look for RFA, RFI, and RFO series

http://www.dwyer-inst.com
Look for series SF series

 

 In these meters, the flow rotates a paddle wheel which in turn produces an electronic output signal that is proportional to the flow rate.

Some models can handle the full range of solar thermal temperatures and pressures.

$150 and up -- maybe the cheapest flow meters with electronic output?
Clamp on Flow Meter

http://www.aquaticeco.com

 

 Drill a hole in the pipe that is to have its flow measured, and clamp this meter on.

$50 -- up to 120F.