In-Situ Measuring Campaign at the Hydropower Plant ‘‘Perućica’’, Montenegro - Part 1: Open Channel System - page 4
Overall error estimation for Diver measurement points: Δ_{total} = Δ_{diver} + Δ_{baro-diver} + Δ_{hand-held gauge} + Δ_{ref.point2- ref.point1} + Δ_{ref.point1-ref.Sea.Level} Δ_{diver} = 0.1% full scale (10m) = 1 [cm] Δ_{baro-diver} = 0.1% full scale (10m) = 1 [cm] Δ_{hand-held gauge} = 0.5 [cm] Δ_{ref.point2- ref.point1} = 0.5 [cm] Δ_{ref.point1-ref.Sea.Level} = 0.5 [cm] Provided that all the errors are in the same direction, so that all the particular errors are positive ("+") or that all are negative ("-"), the overall error would reach the value of Δ_{total} = 3.5 cm. Since in most cases a proper distribution of points (around the exact measurement value) occurs, the expected error is calculated by applying the rules of Gauss's normal distribution and standard deviation for calculating errors. |
The sum of errors Δ_{ref.point1-ref.Sea.Level} and Δ_{ref.point2- ref.point1} represents an error in defining the elevation, and its maximum is 1 [cm]; their influence on the overall error is Δ_{const} = 1 [cm]. Errors Δ_{diver}, Δ_{baro-diver} and Δ_{hand-held gauge} behave according to the normal distribution; their influence on the overall error is: Max. expected error: Δ = Δ_{const} + Δ_{vary} = 1 + 1.5 = 2.5 [cm]. An Ultrasonic E+H level sensor with data acquisition E+H minilog B was used at one measurement point (Figure 1, point 8.1). The ultrasonic sensor was placed above the water surface (Figure 5). |
Figure 5: An ultrasonic level meter measurement point in the channel
The overall error estimation for the measurement point where an ultrasonic level meter was used (8.3): Δ_{total} = Δ_{US} + Δ_{hand-held gauge} + Δ_{ref.point2-ref.point1} + Δ_{ref.point1-ref.Sea.Level} Δ_{us} = 2 [mm] = 0.2 [cm] Δ_{hand-held gauge} = 0.5 [cm] Δ_{ref.point2- ref.point1} = 0.5 [cm] Δ_{ref.point1-ref.Sea.Level} = 0.5 [cm] Δ_{mm} = 8 [mm] = 0.8 [cm] /error caused by logger device; its value is 0.1% f.s. Provided that all the errors are in the same direction, so that all the particular errors are positive ("+") or that all are negative ("-"), the overall error would reach the value of Δ_{total} = 2.5 cm. Since in most cases a proper distribution of points (around the exact measurement value) occurs, the expected error is calculated by applying the rules of Gauss's normal distribution and standard deviation for calculating errors. |
The sum of errors Δ_{ref.point1-ref.Sea.Level} and Δ_{ref.point2-ref.point1} represents an error in defining the elevation, and its maximum is 1 [cm]; their influence on the overall error is Δ_{const} = 1 [cm]. Errors Δ_{US}, Δ_{hand-held gauge} and Δ_{mm} behave according to the normal distribution; their influence on the overall error is: Max. expected error: Δ = Δ_{const} + Δ_{vary} = 1 + 0.96 = 1.96 [cm] Gate position The use of existing equipment to mark the gate position (Figure 6) was planned, but in the case of the Krupac dam this was not possible (Figure 7). |
Figure 6: Display of the segment gate at Slano dam |
Figure 7: Operating wheel of the needle valve with the destroyed scale at Krupac dam |