Contact-related error in the specified readout circuit

Draw the oil-level readout before assigning contact error

An oil-level resistor card is observed through a source, resistive path, wiper or collector and receiver. Locate every contact resistance in that topology. A wiper-to-track term may sit in series with the receiver, while terminal and collector terms can alter the divider legs. Treating all contact resistance as one percentage of total track value gives the wrong sign or magnitude in many circuits. Define the physical position at which the calculation applies and state whether the desired output is voltage, resistance or inferred liquid level.

Solve the network with contact terms included

For a simple divider, one possible loaded form is Vo = Vs(R2+Rc2)/(R1+Rc1+R2+Rc2), but the project schematic may require a different equation. An illustrative 1 kOhm over 1 kOhm divider gives 2.5 V from 5 V. Adding 20 ohms only to the lower branch gives about 2.525 V before receiver loading. That 25 mV is not yet a level error; it must be passed through the local inverse calibration slope. Preserve units and node definitions, and check zero-contact and infinite-load limits.

Calculate contact influence at several track positions

The fraction of upper and lower track resistance changes with wiper position, so one contact term can matter most near an endpoint. Evaluate the network at required calibration points and at any steep inverse-slope region. If the receiver converts voltage to level through a piecewise table, use the local segment rather than a global full-scale percentage. A constant millivolt shift can represent very different level errors in different regions. Include source and component tolerances separately so contact resistance is not blamed for the entire worst-case budget.

Attach every resistance bound to an oil and motion state

Contact behavior may differ dry, immediately wetted, after dwell, on first sweep and during repeated motion. Define which state produces Rc,min and Rc,max. Do not use an arbitrary wide bound copied from another contact system. Where direct contact resistance cannot be isolated, infer a bounded term from fixed-position circuit comparisons and document the model. Oil temperature, additives and contamination remain project inputs. The calculation does not establish chemical compatibility or wear life.

Measure track, contacts and output at matching coordinates

At a fixture-defined position, capture source voltage, loaded output and any accessible four-wire track or terminal observations. Repeat without motion, after controlled motion and after remounting. Use a high-input-impedance measurement only as a comparison, not as a replacement for installed loading. A stable total track resistance with moving output suggests contact or circuit effects; a track-wide shift needs a different investigation. Keep timing aligned because settling or filtering can resemble contact recovery.

Distinguish offset, noise and intermittent continuity

A smooth, position-dependent bias can follow a bounded series term. Random scatter at dwell may indicate an unstable contact film or instrument noise. A dropout at a fixed physical position may be local surface or segmentation behavior. An error that changes when the meter is replaced implicates loading. Diagnose these patterns before assigning one contact-resistance number to all of them.

Allocate contact error without double counting

Place source, track geometry, contact, terminal, receiver and calibration uncertainty in one budget. If a measured output already includes contact variation, do not add the same term again from a separate estimate. Preserve correlations: the same temperature or media state may move several resistances together. Compute nominal, bounded and sensitivity cases. Report whether the result is a voltage deviation, resistance deviation or converted level error, together with the local slope used.

Send the topology and raw fixed-position observations

The RFQ should provide the circuit schematic, source and receiver ranges, nominal track segments, contact construction, oil condition, motion sequence and required output-versus-level function. Include raw values at known positions before and after exposure, not only a fitted gauge curve. State acceptable error, noise and dropout behavior with ownership. Changes to oil, wiper, collector, track, terminal, receiver or calibration table reopen the calculation. The card supplier can review the printed and contact interfaces against these inputs; complete oil-level system performance remains a customer validation.

For a useful vehicle-level calculation, distinguish the oil volume that can actually reach the sump from oil temporarily retained in galleries or on surfaces. The sender may report a stable local height while total recoverable volume changes during drain-back. Define the required soak time, temperature window and attitude before assigning an electrical reading to a service threshold. When a warning threshold is involved, evaluate the contact footprint on both sides of the nominal crossing and include resistance tolerance, supply tolerance and receiver threshold error in the margin. Retain upward and downward traces; their separation can reveal float friction or linkage clearance that a single averaged curve conceals. The final worksheet should show the raw height-volume relationship, mechanical transformation and loaded electrical result as three inspectable layers.

When the calculation is used for service diagnostics, preserve the difference between measurement uncertainty and allowed system error. The first describes knowledge of the observed value; the second is an engineering requirement owned by the application. A guard band can keep uncertain readings away from a decision threshold, but its size must follow the project uncertainty and risk policy. Document rounding only after conversion to level, because early rounding of voltage or resistance can create an artificial step in a shallow part of the tank curve.