Float-Sensor Tracks: Mapping Liquid Height to Mechanical Travel

Define the level coordinate and the pivot

Choose a fixed reference plane for liquid height, normally tied to the installed tank geometry. Locate the arm pivot relative to that plane and specify the assembly orientation. A sensor installed on a tilted flange can have a different height-to-angle relationship from the same mechanism on a level bench.

State whether the geometry uses the float center, attachment point or another reference. The liquid surface is not generally at that point. The float's immersion and orientation must be included to relate its geometric position to actual liquid height. Keep units and angle convention explicit, including the direction of increasing level.

Use the trigonometric relationship of a simple arm

For an ideal rigid arm of length L rotating about a fixed pivot, the float-center height is pivot height plus L times the sine of the arm angle measured from horizontal. If the float center sits a distance d above the liquid surface, liquid height is that center height minus d. This is a geometric starting model, not a complete force equilibrium.

For a hypothetical 100-millimeter arm with constant immersion offset, moving from minus 30 degrees to plus 30 degrees changes center height by 100 millimeters. Equal angle steps do not produce equal height steps because the sine function is nonlinear. Calculate the actual target heights and corresponding angles rather than drawing an evenly spaced electrical curve by assumption.

Check whether the immersion offset remains constant

Buoyant force depends on displaced liquid volume and liquid density, as described by Archimedes' principle. A float connected to an arm also responds to arm weight, contact force and pivot friction. Its immersion can therefore differ from that of a freely floating object with the same shape.

Use the intended liquid density and temperature range when evaluating equilibrium. If the fluid changes, the same float may sit at a different depth and alter the height map. Measure actual static angle versus level where the force balance is too complex for a reliable simple model. Do not treat a geometric centerline calculation as proof that the float follows the liquid surface without error.

Identify regions where angle becomes sensitive to height

Differentiating the arm model gives height change per angle as L times cosine of theta, with angle in radians. Near horizontal, a given angle change produces a relatively large height change. Near a vertical arm position, the same angle change produces little height change, and the inverse height-to-angle mapping becomes sensitive to small height or geometry errors.

Avoid extending a simple inverse sine calculation across a turning point without checking which physical branch the mechanism follows. A useful sensor range should provide an unambiguous relationship between height and track coordinate. If two arm positions correspond to the same height or the float reaches a stop, the electrical curve cannot restore a unique mechanical measurement.

Resolve mechanical constraints before defining resistance points

Use the height map to compare the proposed geometry with the actual tank envelope. The float needs room to move, and the wiper must remain on the intended track over the resulting angular range. Constraints at either interface can limit useful measurement.

Translate arm angle into the card's own coordinate

The wiper may rotate directly with the arm or through a linkage. Define that transfer explicitly, including any offset or ratio. The card's electrical zero must correspond to the installed mechanical index, not simply to an arbitrary end of its printed arc.

Combine the maps in order: liquid height to arm position, arm position to wiper coordinate, then wiper coordinate to electrical output. Retaining the intermediate values makes errors easier to diagnose. If the final output is wrong, the engineer can determine whether the discrepancy begins in float motion, coupling alignment or the resistance curve rather than changing all three together.

Verify the map with rising and falling level

In a controlled test arrangement, record actual level, arm angle and electrical output as level rises and falls. Allow the agreed settling time at each point and preserve the liquid condition. A difference between rising and falling angle at the same level can indicate friction, contact force or mechanical interference.

Keep dynamic slosh evaluation separate from this static mapping. A transient liquid surface can move the float and produce a valid instantaneous response that differs from the desired displayed level. Mechanical damping and signal filtering change that response and need their own timing requirements. They should not be used to conceal an incorrect static height-to-travel conversion.

Keep liquid height separate from stored volume

A level sensor directly follows a height-related mechanical quantity. The volume represented by that height depends on tank shape and orientation. A rectangular tank may have a simple relationship, while a tapered or irregular tank does not. Preserve the height map as an independent input to any later volume calibration.

For quotation, send the tank envelope, pivot and float details together with required height points. Include usable empty and full definitions, because physical tank boundaries may not match operating limits. This lets the track travel and output curve be reviewed against the real mechanism. A resistor card can implement the agreed electrical relationship only after the mechanical conversion is sufficiently defined.