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Fault injection is useful only when the injected condition, location, duration and expected observation are controlled. Opening a sensor lead at a bench connector does not necessarily represent an internal track interruption, and shorting an output can exercise protection that masks the intended mechanism. A rigorous plan begins with architecture-owned faults, inserts each at a named boundary, records raw and processed channels, and restores the system safely. Observed detection supports that test case; it does not by itself establish diagnostic coverage or a functional-safety rating.
System boundary
A resistive or thick-film sensor element, mechanics, terminals, harness, receiver, controller software, actuator response and safe test environment. ChipSimple owns drawing-defined card manufacture only; vehicle architecture and safety validation remain customer-controlled.
System integration decisions
- Derive injected cases from the system hazard and diagnostic analysis.
- Locate every injection relative to sensor, harness, receiver and protection.
- Separate detection observation from safety-rating and coverage claims.
Translate architecture faults into injectable electrical states
For each case, name physical hypothesis, electrical equivalent, insertion point, polarity, resistance or impedance, timing and recovery. Examples can include open conductor, short to supply or return, cross-channel bridge, bounded series resistance, mechanical position offset or intermittent contact. Not every internal failure is equivalent to a connector switch. Mark faults that cannot be represented without special specimens. The customer hazard and diagnostic analysis selects required cases; this page does not create a generic automotive list.
Calculate the injected node before connecting hardware
Insert injector resistance and parasitic capacitance into the actual receiver circuit and solve expected voltage or current. Include pull networks, clamps and supply impedance. Compare normal and injected states with system-owned thresholds.
V_f=solve[Circuit,R_f,C_f,state]; M_f=V_f-V_threshold
- R_f and C_f represent the characterized injector and intended fault path.
- state includes supply, sensor position and receiver mode.
- V_f is predicted receiver-node response.
- M_f is signed separation from the applicable system threshold.
The equivalent circuit represents the physical fault and nonlinear protection is included where active.
Document one bounded series-fault example
Consider an illustrative signal path carrying 0.4 mA into its receiver. Adding a controlled 1.0 kΩ series injection produces a first-order 0.4 V drop if current remains unchanged. If receiver bias changes current, the complete circuit must be solved instead. Suppose the system threshold margin before uncertainty is 0.25 V; this example predicts threshold crossing, but only the actual recorded response can verify it. Values are educational and do not define an automotive product or safety requirement.
Vary position, supply, time and operating mode
Run faults at positions where normal signal is closest to each threshold and at modes with different pull networks or diagnostics. Include startup, steady operation and transitions as required. Define persistent and intermittent durations relative to sampling and filter windows. Test supply and temperature states from the authorized plan. Randomly toggling faults without state control can miss boundary behavior and creates unreviewable evidence.
| Field | Required detail | Reason |
|---|---|---|
| Physical fault hypothesis | Location and mechanism | Establish representativeness |
| Electrical injection | Nodes, impedance and parasitics | Predict receiver response |
| System state | Position, supply, mode and timing | Control detection opportunity |
| Observed response | Raw signal, diagnostic and actuation | Separate evidence layers |
Characterize injection equipment and wiring
Measure switch on-resistance, off leakage, capacitance, lead impedance and isolation. An electronic multiplexer can add paths absent from a manual connector fault. Place voltage observations on both sides of the injector where possible. Synchronize trigger, raw sensor, processed value, diagnostic status and system response. Verify safe restoration after power or communication loss. The fixture should fail to a state defined by the authorized test owner, not one assumed by the page author.
Report observed detection without extrapolating coverage
State whether the raw signal changed as predicted, when software recognized it, which diagnostic code or state appeared and what controlled response followed. A pass applies to the specific fault, state, duration and configuration. Absence of detection can reflect an unrepresentative injection, threshold, timing or architecture gap. Detection of one short does not prove all resistive bridges or intermittent events. Coverage metrics require the customer's complete fault population and analysis.
Keep fault testing inside authorized vehicle-safety controls
Use bench or hardware-in-loop environments unless the responsible organization authorizes another setting. Faults can command actuators, disable protections, heat wiring or damage electronics. Apply isolation, current limits, interlocks and emergency recovery from the site procedure. Do not bypass safety mechanisms to obtain a desired diagnostic. ChipSimple cannot certify a vehicle function, safety level or regulatory result from a sensor-card fault test.
Release traceability from fault hypothesis to observed response
Control schematic and pin map, injector design, software, calibration, sensor position, supply, temperature, timing, test environment, raw traces and expected results. Link each case to customer-owned requirements without exposing private safety analysis publicly. ChipSimple can support card-level electrical assumptions and special drawing-defined specimens; the customer owns hazard analysis, diagnostic thresholds, coverage and vehicle release. Reopen cases after changes to sensor, harness, protection, receiver, software or actuator response.
Complete the application-specific release check
Before concluding a case, verify injector removal and baseline restoration, then inspect whether protection or latching changed the subsequent system state. Repeat representative cases at boundary positions and timing phases selected by the customer analysis. Record faults that could not be safely or faithfully injected and leave them open rather than marking them passed. If a special resistor-card specimen represents an internal open or bridge, document its geometry and measured equivalence. This transparency allows safety engineers to integrate the evidence without treating a convenient bench switch as universal fault coverage.
Provide the customer-controlled fault and interface matrix
Fault-injection support requires exact nodes and test ownership without transferring safety authority.
- Sensor schematic, terminals, mechanics, harness and receiver protection.
- Required fault hypotheses, injection nodes, impedances and durations.
- Operating states, sampling, filters, thresholds and expected observations.
- Safe test environment, recovery procedure and functional-safety owner.
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