Xylem H-335 - Manual (Page 7)

H-335
H-335 Operation 1-3
1.4 Gate Geometry
Most users are interested in measuring the gate opening or “height”. Upon closer examination, however, the
geometry of a tainter gate is somewhat complex. The following definitions and illustration shows the
geometry of a typical tainter gate.
1.4.1 Terms and Definitions
Trunnion Bearing: The pivot point of the gate structure.
Sill Elevation: The elevation relative to a datum of the point where the gate seals against the
bottom of the spillway.
Gate Radius: The distance between the center of the trunnion bearing and the outside of the gate
skin plate.
Gate Angle: The angle, in degrees, through which the gate has opened (0 = closed).
Gate Arc Length: The distance the gate face moves through the partial curve of a circle.
Gate Height: The vertical distance between the bottom of the gate and a horizontal line passing
through the sill.
Sill Angle: The angle, in degrees, between a horizontal line through the trunnion bearing and
the point at which the gate rests on the spillway.
The tilt sensor in the H-335 measures the angle of the gate structure referenced to gravity. The H-335 can
be installed anywhere on the gate structure since the entire structure rotates the same relative to gravity.
The sensor does not need to be on the center of the gate’s rotating axis.
The H-335 measures and reports the UserAngle relative to the closed position (0 = closed). For
convenience, the H-335 also internally calculates and reports GateHeight and GateArcLength. Normally,
users program their data recorder to record only one of the three parameters. Each of these three
measurement parameters has advantages and disadvantages: