Iowa | dloc - 5/11/2008 19:28
Standard Fairbanks truck scales will have a total error of < 0.02%. The Elite Coriolis flow meter from Emerson has a rated error of +/- 0.05%. A truck scale is a single static measurement so error is easy to define. For the load plus the tare - so 80,000 pounds times 0.0002 equals less than 16 pounds. A flow meter sums a signal over the load time so accuracy is a function of the rate of flow plus a bunch of other factors (temperature, density, etc.). For a load of 50,000 pounds times 0.0005 equals 25 pounds.
In my opinion, I'd still take a mass flowmeter over a truck scale. A brand new truck scale is one thing, but I have observed a number of truck scales across the countryside that do not appear to have the stability equated to the +/- 0.02% mark.
dloc - 5/11/2008 19:28
I don’t know of any farm chemical companies that use flow meters of this quality so errors are more likely to be at least 10x worse. Plus, flow meters are difficult to calibrate well and susceptable to manipulation by changing flow rates or other parameters, intentionally or not.
Kahler Automation and Dultmeier Sales, two common names in chemical handling across retailers, Co-ops, etc. use MicroMotion Elite series meters. Miller Mechanical has done some work with E+H meters at chemical distribution facilities. |
make sure you get what you pay for
