During EMC compliance validations we monitor DUT (Device Under Test) errors visible for the occupant in vehicle in parallel with stored or not
stored yet DTC (Diagnostic Trouble Codes). Disruptions in data
bus or communication bus that do not set a DTC are not visible for the end
user, since many of them are controlled safely by Vehicle Software & BCM.
The driver can be distracted by vehicle cluster signs/indicators turning red, like an imminent hazard.
- If the incident
self-recovers, it may not be a problem but it depends on DUT's Classification and Required Immunity Level.
- If the DUT does not
self-recover and require driver's intervention, then the LS support software must mimic
the user response to resume operation (automation). Such anomaly is marked in a data log but should not be a reason to stop on-going testing.
- If the DUT does not
self-recover requiring Hard Reset (VBATT on-off-on), then it's really bad. This is like a stop show but make sure it is always driven by DUT, never the LS.
- The pass/fail
criteria mentioned in EMC test plan must guide your LS design effort,
especially to decide on what type of FO monitoring equipment is needed.
- Ideally is to use
production intent DUT's I/O loading and Vehicle Software reducing the entire effort to monitoring the communication bus & FO equipment (e.g. FO Voltage
Probes, FO Signal/Data Probe).
- The moment you’re
forced to use excessive HW/SW simulation, you practically spend more time
validating the Load Simulator instead of focusing on DUT's EMC performance.
- If possible, avoid using active electronic components for the LS placed inside ALSE chamber.
- Use production intent loads, ideally EMC validated by OEM.
- Use FO devices that are certified for 200 V/m, CISPR 25, 30KV ESD.
- The support software should not stop the show if errors occur, only the DUT
should be able to stop the show.
- Pay attention how is the shielding of I/O lines terminated/grounded in vehicle
and use if possible production intent cables and proper wire gauge.
- For remote grounded module, make sure the only possible connection to battery negative pole is via supply
- The LS metallic enclosure is bonded to GP (ground plane) as shield.
- The LS metallic enclosure is not being used as grounding point for DUT or LS electronics.
- All signal return
lines are closed to their source, never to GP.
Christian Rosu, Sep 28, 2020.