This calculator performs interval arithmetic on a user-supplied calibration: adjustment movement multiplied by low and high sensitivity values. It does not derive weir sensitivity, gate angle, water level or discharge from physical design data.
Self-acting Weir Calibration Envelope
Apply a measured low/high sensitivity interval to an adjustment move. The animation separately illustrates a float-and-cable gate response.
Equation Used
- Sensitivity bounds are user-supplied empirical calibration values.
- Sensitivity is treated as linear over the entered adjustment move.
- The calculation propagates only the selected interval.
- Gate equilibrium, hydraulics, dynamics and structural loads are not calculated.
Use sensitivity values only when they are supported by measurements for the specific installation.
Float chamber and cable drums
A mechanical automatic tilting weir may connect a float/counterweight in an upstream-level enclosure to a tilting gate through a cable transmission. Rising water changes float buoyancy while also changing hydraulic force on the gate; their moments determine gate inclination.
Two drums share a shaft: payout toward the gate winds up the float cable. The gate pivots below its midpoint. The illustration uses selected proportions and an illustrative water-rise sequence; gate angle is not calculated from the calibration inputs.
What the calculator determines
Enter an adjustment movement Δx and a low/high empirical sensitivity interval. The calculator reports the signed lower, midpoint and upper level-shift estimates plus interval width.
This can record a measured calibration range for one known installation. It is not transferable design data unless supported by measurements for that mechanism.
Calibration-envelope arithmetic
Let slo = min(sL, sH) and shi = max(sL, sH). The two endpoint products are Δx slo and Δx shi; the reported lower and upper values are their numerical minimum and maximum. Midpoint is Δx(slo+shi)/2.
Selected-input arithmetic
For a +10 mm adjustment and a selected sensitivity range of 0.30–0.50 mm/mm, the assumed level-shift interval is +3 to +5 mm, midpoint +4 mm. These numbers come from the entered calibration, not from a hydraulic model.
Calibration and physical design
A defensible self-acting-weir calculation would require gate geometry and mass, pivot and cable geometry, float volume and mass, counterweight, upstream and downstream water depths, hydrostatic pressure distribution, discharge geometry, friction, damping, stops and loss coefficients. None are supplied.
The entered calibration therefore cannot establish gate equilibrium, regulated water level, discharge, stability or structural loads. Use measurements from the particular installation when choosing the sensitivity interval.
Questions
Where do the sensitivity values come from?
They must come from documented measurements or a separate validated model; this calculator does not derive them.
Why are negative moves supported?
The interval arithmetic preserves sign and reverses endpoint ordering correctly.
Can this size or commission a weir?
No.
References & Further Reading
Mechanical automatic tilting weir, WO1989002006A1, figures 1–3: float chamber, coaxial cable transmission and tilting gate.
- Wikipedia contributors. Weir. Wikipedia
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