Interface requirements for sensor-card dead-zone control

System boundary

External mechanism and stops through wiper travel, conductor-to-resistor transitions, terminal circuit, acquisition limits and controller state logic

Give each zone a functional name

Define mechanical overtravel, contact approach, terminal transition, active measurement, diagnostic band and prohibited travel separately. Assign coordinate limits and required output state to each. Avoid using “dead zone” for every region outside nominal linear output.

State whether each boundary is a target, minimum reserve or maximum allowed interval. Include lower and upper ends independently because geometry and routing can differ. The system owner identifies which zones are reachable in normal service.

Map all boundaries into one coordinate

Choose shaft angle, slider displacement or another installed coordinate with defined datum, direction and uncertainty. Provide the transformation from that coordinate to wiper location. Backlash and leverage can make a fixed artwork distance correspond to different system intervals.

Measure approach from both directions. Record stop compliance, carrier deflection and contact footprint rather than treating the wiper as a dimensionless point. A change in contact geometry can shift effective entry without moving the nominal centerline.

Calculate usable span after explicit reserves

If total contact travel is L_total, and lower reserve, upper reserve and transition allocations are L_low, L_high and L_trans, the nominal usable span is L_use=L_total-L_low-L_high-L_trans. Define whether transition is counted once or at both ends.

For an illustrative 60 millimetre travel with 3 millimetres lower reserve, 4 millimetres upper reserve and 5 millimetres total transition, usable span is 48 millimetres. This is a calculation example only; actual allocations require the released mechanism and pattern.

Specify conductor-to-active-track behavior

Define expected resistance or voltage as the contact enters the printed network, crosses conductor overlap and reaches the active region. Name the terminals, excitation and test current. State allowable continuity behavior and monotonicity in the transition.

Overglaze, conductor geometry, contact footprint and alignment can influence the transition. Any permitted inactive region should appear on the artwork and interface drawing, not only in controller code.

Define how the controller interprets every region

List raw input limits for valid, transitional, invalid-low, invalid-high and open-circuit states. Include saturation, diagnostic debounce, hysteresis, startup and recovery. A clamped analog input can make overtravel look like a legitimate endpoint.

Keep raw input available for validation. If software substitutes the last valid value or a default, name that behavior and its time limit. System response and safe state are integrator decisions.

Distinguish the origins of an apparent dead zone

Observe external coordinate, wiper coordinate, terminal value, analog input and reported state together. Determine where motion first occurs and where electrical response first changes.

Repeat in both directions and under relevant load. Do not change curve scaling until stop, backlash, contact entry and input clipping have been separated.

Plot boundary position for several approach speeds and dwell times. A fixed terminal transition with a moving software transition challenges timing or debounce, while a load-dependent mechanical transition challenges stop compliance or linkage. Record the coordinate uncertainty at each observation. Without that information, a small apparent zone change may be fixture variation rather than a product or controller effect.

Allocate boundary uncertainty

Include stop location, linkage ratio, carrier placement, substrate position, artwork registration, contact footprint and coordinate-fixture uncertainty. Report contributors and correlation rather than hiding them in one rounded margin.

Check worst credible combinations at both ends. A nominally generous reserve can disappear when several one-sided tolerances align. Statistical combination requires a justified distribution and process evidence.

Validate entry, exit and overtravel behavior

Approach every boundary from both directions at specified speeds and loads. Pause inside transition regions, exercise mechanical overtravel and capture terminals, analog input and controller state on a common time base.

Freeze coordinates, limits, uncertainty and invalid-run rules before testing. Confirm on assemblies not used to tune thresholds. The result applies to the identified revisions and does not establish lifetime or safety certification.

Use fixtures that allow the actual stop to engage without transferring unintended force into the card. Check recovery after leaving overtravel and after power cycling while positioned in each transitional band. Verify that service diagnostics display the intended state and preserve enough raw information to distinguish an invalid electrical region from a mechanically blocked mechanism.

Dead-zone verification needs one shared coordinate system spanning the mechanical stop, contact touchdown, valid electrical region and controller interpretation. Approach each boundary slowly from both directions while recording independent position and raw output. Separate a deliberately reserved inactive arc from lost motion, contact lift or an input threshold inside the controller. Repeat with permitted assembly-index extremes so the usable region is not judged only at nominal alignment. If the controller clamps, filters or substitutes values near an endpoint, preserve the unprocessed channel for analysis. The interface owner defines the allowable inactive interval and safe response. The printed card supplier can review drawing coordinates, but cannot establish the assembled mechanism’s final dead zone without housing, carrier and readout information.

Control revisions that move a boundary

Link stops, linkage, wiper, artwork, mounting, terminals, acquisition and software band revisions. Recheck the allocation if any item changes even when total resistance remains the same.

Review false endpoint, undetected overtravel, delayed recovery and non-monotonic transition separately. Assign consequence, detection and fallback to the system owner. Missing mechanism data remains an open interface input.

RFQ inputs for dead-zone control

Provide common coordinate, datums, full travel, stops, overtravel, linkage, wiper footprint and lower and upper zone allocations. Include artwork transitions and terminal behavior.

Submit acquisition limits, controller state table, direction, speed, load, environment, validation method, quantities and ownership. Identify any region whose output is still undecided.