Martin, As you suspect, installing the sensor so close to the guide vanes is not a good idea if you need accurate results. The signal will fluctuate and you may need some additional circuitry to smoothen your signal. If you go ahead, remember installing a shut-off cock between the tapping and the sensor. There is also a certain geometry, which should be adhered to for the tapping point for accuracy and corrosion protection (i.e. a stainless steel insert with 5mm hole on the inside and the tapped 1/2" (?) connection on the outside, so that the "flow" path is only 5 mm diameter) .
Why don’t you consider installing a submersible pressure sensor well upstream of the turbine in a sleeve pipe, maybe in the intake bay if your pressure conduit is short? BTW, You will also need a sensor for the tail water level to determine the net head of the turbine. Mike > -----Original Message----- > From: [email protected] > [mailto:[EMAIL PROTECTED] On Behalf Of Martin.Leahy > Sent: Wednesday, October 26, 2005 16:24 > To: '[email protected]' > Cc: '[EMAIL PROTECTED]' > 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 > > > > > > > ------------------------ Yahoo! Groups Sponsor > --------------------~--> Get fast access to your favorite > Yahoo! Groups. Make Yahoo! your home page > http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/FGYolB/TM > -------------------------------------------------------------- > ------~-> > > 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! > > NOTE: The advertisements in this email are added by > Yahoogroups who provides us with free email group services. > The microhydro-group does not endorse products or support the > advertisements in any way. > > More information on micro hydropower at http://microhydropower.net > > To unsubscribe: send empty message to > [EMAIL PROTECTED] > Yahoo! Groups Links > > > > > > ___________________________________________________________ Gesendet von Yahoo! Mail - Jetzt mit 1GB Speicher kostenlos - Hier anmelden: http://mail.yahoo.de ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. 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