Martin: Those pressure sensors with remote report capabilities with such accuracy are expensive.
You need to look for those in the 0.5 to 1 % precision that have a much lower price, also with restricted distance reporting capability if possible. Vanes adjustments are around 2 to 4 % accurate unless the controlling equipment has MPPT determination and control to peak the power generated. One way to avoid the turbulence is to attach a pipe with a small hole restriction to slow down the turbulence at your point of interest and have enough water in the pipe to reduce the pressure variations, ratio reduction = ( Diameter of pipe) / ( diameter of hole). Regards Nando ----- Original Message ----- From: "Martin.Leahy" <[EMAIL PROTECTED]> To: <[email protected]> Cc: <[EMAIL PROTECTED]> Sent: Wednesday, October 26, 2005 7:53 AM Subject: [microhydro] Head sensor for hydro I have a site with 450 mm (18 inch) Francis turbine housed in a pressurised concrete water chamber (approx. 2.5 m x2.5 x 2.5m) and GE F650 bay controller. Head varies between 9 and 6 m and I would like to measure and use this head in control of the turbine guide vanes. I can easily install a pressure sensor by drilling and tapping into the access panel of the chamber about 0.5 m from the nearest guide vane. I am concerned about the turbulence (although this may be averaged out). Also, the spec I guess should be stainless steel, 4 - 20 mA o/p, 0-1 bar. There appears to be a large differential in prices (see below from RS). Regards, Martin ****************************************************** Cable stock no. price each Range Length 1+ 0 to 5m WG 15 m 395-7101 € 336,00 0 to 10m WG 15 m 395-7117 € 336,00 0 to 20m WG 25 m 395-7123 € 379,00 Water head pressure equals 100mbar per metre which can be effectively measured using submersible pressure transmitters in atmospheric tanks. Output is proportional to level. High accuracy Easy installation Measures tanks and boreholes technical specification Signal Output 4-20mA Zero/Span Tolerance 0·1% Supply Voltage 8 to 40Vdc Operating Temperature -20°C to +85°C Long Term Drift 0·15% of max span/year Accuracy 0·15% FS Max Overpressure 2 x FS Rating IP68 ************************************************* GP Pressure Transducers/Transmitters: One piece stainless steel body Multipurpose, high performance Temperature compensated, strain gauge technology 0-100mV output (transducers) 4-20mA output (transmitters) 0-5V output (transducers) technical specification Over working pressure 2 x range (x5 burst pressure) (max) Accuracy ±0.25% (typ) Excitation Voltage 10Vd.c. (0-100mV transducers) 6·5-35Vd.c. (0-5V transducers) 7·5-35Vd.c. (4-20mA transmitters) Output (transducers) 0-100mV 0-5V Output (transmitters) 4-20mA Operating range -40 to +125°C (transducers) -40 to +100°C (transmitters) stock no. price each transducers conn. (0-100mV) 1+ 6+ 0-1 bar g 1/4 BSP 249-3864 € 132,50 € 127,00 0-6 bar g 1/4 BSP 249-3959 € 132,50 € 127,00 0-10 bar g 1/4 BSP 249-3858 € 132,50 € 127,00 0-25 bar g 1/4 BSP 249-3965 € 132,50 € 127,00 0-40 bar g 1/4 BSP 249-3836 € 132,50 € 127,00 0-100 bar g 1/4 BSP 249-3820 € 132,50 € 127,00 0-250 bar g 1/4 BSP 249-3971 € 132,50 € 127,00 0-400 bar g 1/4 BSP 348-8217 € 132,50 € 127,00 transmitters conn. (4-20mA) 0-1 bar g 1/4 BSP 249-3870 € 162,00 € 155,00 0-6 bar g 1/4 BSP 249-3943 € 162,00 € 155,00 0-10 bar g 1/4 BSP 249-3937 € 162,00 € 155,00 0-25 bar g 1/4 BSP 249-3921 € 162,00 € 155,00 ******************************************************** ********************************************************** Kind Regards, Martin Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! 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