Nonuniform tank area and sender kinematics

Keep tank volume and sender motion as two functions

A fuel gauge joins two different maps. Tank geometry determines volume V as a function of liquid height h; float and linkage geometry determine sender coordinate x as a function of h. The electrical network then maps x to resistance or voltage. Combining all three into one fitted curve makes error ownership impossible. Build V(h) from the installed tank section or traceable fill calibration. Build x(h) from simultaneous height, angle and contact observations. Only then solve for the electrical function that supports the required indication. Baffles, sumps, trapped volume and vehicle attitude belong to the tank map; pivot, arm, float and friction belong to the sender map.

Integrate changing tank area instead of assuming equal height steps

For an upright tank, volume between two heights is the integral of horizontal cross-sectional area A(z). Equal height increments represent equal volume only if A remains constant. An illustrative tank with areas of 220, 310 and 180 square centimetres over successive 10 mm bands contains 220, 310 and 180 cubic centimetres in those bands. That arithmetic is a unit check, not a supplied tank model. Use measured geometry or controlled fill quantities for the real table. Where a baffle divides regions, establish whether liquid equalizes during the measurement. A static CAD volume can differ from usable volume when the installation traps or excludes liquid.

Map each calibrated height into the contact coordinate

At every controlled liquid height, observe float attitude, arm angle and wiper coordinate. A circular arm arc produces nonlinear travel, and float immersion can alter the relationship further. Retain fill and drain branches so friction is visible. If the electrical card cannot be observed directly, validate any geometric surrogate against assembled contact impressions or another independent method. The contact footprint must remain within permitted regions at the lowest and highest mechanically reachable states. Do not assign electrical knots to tank heights that the mechanism cannot repeat under the specified liquid density and orientation.

Join the maps with monotonic piecewise data

Create ordered records containing volume, height, arm angle, contact position and unloaded electrical value. Choose interpolation separately for each link and state its endpoint policy. Closely spaced knots are valuable where tank area or linkage sensitivity changes rapidly; equal spacing is not inherently better. Reserve independent points between fitted knots to reveal interpolation error. If the combined relation is not monotonic, determine whether the cause is real tank geometry, mechanical hysteresis, electrical segmentation or a measurement defect. Smoothing a reversal without explanation can create a display that looks orderly while misrepresenting actual volume.

Apply the receiver only after the passive map is understood

A bench resistance curve does not automatically equal installed gauge response. Source tolerance, pull-up resistance, receiver impedance, filtering and ratiometric conversion can alter the observed voltage. Preserve raw resistance or segment data and solve the approved circuit at every calibration coordinate. Evaluate local sensitivity dVout/dVfuel or its discrete equivalent so an electrical error can be expressed in volume units without assuming one global slope. Saturation and dead zones need explicit handling rather than extrapolation beyond the last supported knot.

Acquire fill and drain data with independent checkpoints

Use measured volume additions or removals, stable orientation and a stated settling rule. Record liquid temperature and density where they materially influence float equilibrium. Capture height, angle, contact coordinate and electrical output on a common time base. Repeat selected points after a complete empty/refill sequence and after sender remounting. Keep several check points out of the curve fit. A residual that follows volume band may indicate tank-area error; one that follows arm angle implicates kinematics; one fixed at a card coordinate points toward the printed path or contact.

Allocate residuals to the map that can cause them

Do not report only final display error. Preserve separate residuals for V(h), x(h) and electrical output. A correct contact coordinate paired with wrong calibrated volume challenges the tank table. A correct height-angle relation but displaced contact challenges the linkage or card datum. Stable mechanics with a local electrical discontinuity challenges track geometry, contact or readout. This ledger lets corrections target the responsible owner and prevents a resistor artwork edit from compensating silently for an incorrect tank calibration.

Release three linked revisions and a bounded RFQ

The handoff should include tank geometry or calibration, installed attitudes, liquid conditions, float and pivot dimensions, measured kinematics, contact footprint, printed curve, receiver circuit and desired volume indication. Give each table a revision and declare which interpolation and endpoint rules apply. Changes to tank, baffle, sender mounting, float, linkage, track or display algorithm trigger review at the affected map rather than automatic full redesign. The supplier can assess the resistor-card transfer against supplied inputs; the system owner retains volume calibration, vehicle attitude behavior, diagnostics and complete gauge acceptance.

Before freezing the map, examine the regions around baffles, sumps and pump reservoirs separately. A tank can show a long electrical plateau while liquid is still moving between compartments, then change quickly when a connecting passage becomes active. Record fill direction, dwell time and vehicle attitude with every calibration point. If the gauge controller applies damping, keep the undamped sender curve and the display algorithm as separate records. That distinction lets an investigator decide whether an apparent lag comes from fluid redistribution, contact motion, the printed function, or software filtering. It also prevents a later controller update from being mistaken for a change in the ceramic card. Preserve both the raw volume-height observations and the chosen interpolation knots.