Float assembly position and track datum transfer

Trace the mechanical-to-electrical datum chain

List float centre, arm geometry, pivot axis, mechanical stops, carrier, ceramic locating features, fired track, wiper footprint, and electrical terminals. Define the external level or angle reference if available. Assign coordinate frames to tank or test fixture, pivot, card, and track.

Identify which interface is adjustable. An arm bend, card slot, or wiper carrier adjustment must be recorded as an operation, not absorbed into nominal geometry. Keep customer-supplied mating dimensions conditional until confirmed.

Measure float position without using resistance as the reference

Use an independent angular, linear, or level measurement. Record orientation, buoyancy surrogate, arm load, approach direction, speed, dwell, and stop contact. A fixture that pushes the arm can create a different pivot load from an actual float.

Measure repeat positions from increasing and decreasing directions. Their difference indicates play, friction, or hysteresis in the mechanical chain. Do not average directions before examining the pattern.

Predict wiper travel from pivot and arm geometry

For a simple rigid arm, an angular change maps to arc length at an effective radius. Link that predicted motion to the wiper carrier through the actual mechanism. Offsets, linkages, and noncircular paths require the reviewed geometry rather than the simple arc.

At an effective radius of 40 mm, a 5° change is about 3.49 mm of arc. This example checks units only. Arm deflection, pivot clearance, linkage ratio, and contact motion can change the actual wiper coordinate.

Transfer the predicted position into the card frame

Measure pivot-to-card location, card seating, ceramic functional edge or holes, track origin, and guide orientation. Apply translation and rotation into the fired track frame. Reserve independent track features to verify the transfer.

A card can shift during fastening or enclosure closure. Record coordinates before and after those operations. If software calibration compensates the shift, retain the mechanical residual so mounting margin remains visible.

Use the wiper footprint rather than a centre point

Map contact width, length, orientation, preload, and movement relative to track edges and terminations. At end positions, part of the footprint may enter a conductor, glass boundary, or inactive zone. Calculate usable overlap with tolerances.

Inspect contact marks on development units. A split or angled footprint can make the electrical transition differ from the predicted centre coordinate. Keep track wear and debris outside initial datum claims unless separately studied.

Correlate independent position with electrical response

At planned float positions, record mechanical reference, predicted and measured wiper coordinate where accessible, resistance or voltage, direction, temperature, and stop state. Keep raw data before linearization. Position error and curve-shape error should remain separate.

A constant curve offset suggests zero transfer; growing error suggests scale or arm geometry; direction-dependent error suggests play or friction; a localized jump suggests contact or track condition. Use these signatures to select the next measurement.

Assign deviations to the datum-chain layer

The table prevents final calibration error from being treated as one generic resistor-card issue.

Check datum transfer at more than one fluid condition

Float equilibrium can move when density, temperature, surface tension or attached deposits change, even though the arm and card geometry remain unchanged. Measure independent liquid level and float or arm coordinate in at least the fluid states relevant to the application review. Then transfer that measured mechanical coordinate into the card frame and compare electrical output. Keep vessel attitude and meniscus definition explicit. A curve calibrated in a dry fixture verifies kinematics but not buoyant equilibrium. The result should identify which variation belongs to fluid behavior, pivot or linkage geometry, wiper registration and passive track response, preventing software calibration from concealing a changed physical level reference.

Release the assembled datum and calibration boundary

Control float and arm drawing, pivot, stops, carrier, ceramic mounting, fired track, wiper, coordinate transforms, approach directions, checkpoints, raw curve, adjustments, and disposition. State the liquid or tank conversion boundary separately.

Revalidate after float, arm, pivot, stop, housing, card, track, wiper, fastening, calibration, or test fixture changes. RFQ review needs the actual sender and tank interface. No level accuracy, media compatibility, or life is promised without system evidence.

Evaluate gravitational orientation and float loading separately from the coordinate transform. A bench fixture can support the arm or pivot differently from the installed sender. Record the applied load point and use a representative buoyancy method only when its relationship to service has been reviewed.

Measure stop engagement before calibrating the electrical endpoints. If the mechanical stop is compliant or approached at different speeds, the apparent zero can shift. Use a defined approach and dwell, then record the stop reaction or observable seating condition.

Keep installation adjustment history for each unit. An arm bend can correct one endpoint while changing effective radius and the rest of the curve. Compare pre- and post-adjustment geometry instead of retaining only the successful final sweep.

Where the track includes nonlinear segments, compare mechanical coordinate with the intended local electrical gradient. A small datum shift in a steep region can produce a larger output change than the same shift elsewhere. This is a curve-design interaction, not automatically a printing defect.

Confirm the released datum chain on independent assemblies spanning reviewed tolerance extremes. Include bidirectional motion and multiple seating cycles. If coordinate residuals grow after cycling, separate fastener movement, pivot play, wiper carrier change, and track wear before updating calibration.