good ole ebay...I use pressure as one of my system monitors for my hydro as well as a level gauge for the tank but I have seen them quite cheap on ebay if you catch it at the right time. I even got a flow sensor so I could see how much water I was using
doug ----- Original Message ----- From: "Martin.Leahy" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, October 27, 2005 3:19 AM Subject: RE: [microhydro] Head sensor for hydro > Michael/Nando, > > Thanks for your swift and informative response. > > They are a little expensive especially if I have to buy two. I have not > found pressure transmitters (with 4-20 mA or 0-10V output) for much less > than $150. Would be useful to know if they are available cheaper > elsewhere. > > Placing the first sensor in the reservoir requires an extra 20 m of cable > (and of course burying it), but maybe this is safer and will reduce the > need > to filter the pressure signal. Differential is not really an option since > I > want to know how full the reservoir is and potentially flow into and out > of > from the rate of change of pressure. > > Kind Regards, > > Martin > > -----Original Message----- > From: HYDRO [mailto:[EMAIL PROTECTED] > Sent: 27 October 2005 05:05 > To: [email protected] > Subject: Re: [microhydro] Head sensor for hydro > > 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! > > 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 > > > > > > > > > > > > > > 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 > > > > > > > > > > > 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 > > > > > > > > ------------------------ 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. 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