EMC FLEX BLOG A site dedicated to Automotive EMC Testing for Electronic Modules

CISPR-25 Generic Test Setup for compliance to CS.00054:2018

A few months ago I was surprised that UL lab (Novi, MI) runs RI 115 (Immunity to Hand Portable Transmitters) leaving the ALSE chamber door fully open. I have requested the test engineer to confirm that he follows correctly UL lab internal test procedure. The response was that this is practically near field RF immunity, therefore there is no concern to interfere with other lab test equipment.

CISPR-25 is not very specific about device under test and support equipment configuration during chamber ambient test. The automotive OEM require the ambient for RE, CE-V, CE-I with support equipment energized. The test laboratories will typically disconnect VBATT line from LISN output. The GND line remains connected to LISN. By doing so is assumed that DUT is not energized. The support equipment remains connected to the input of the LISNs being turned on (energized). The CAN bus is powered but w/o traffic. It is unclear if the load simulator energized it means powered but inactive (standby). By activating PWM pulses as inputs for DUT it may yield unwanted CE-I and RE ambient noise. All these aspects must be clarified in the EMC test plan.

In the sample presented the CE-V ambient noise is well below the 6 dB requirement. However, this type of noise is being captured while DUT's integrated buttons are being pressed and released via a pneumatic system with no electrical connection to DUT or test ground plane. Specifying that DUT must be unpowered may not be enough, the DUT's buttons should not be mechanically activated, nor its inputs subjected to electrical signals.

The automotive OEM that certifies EMC laboratories to carry out validation testing invested a lot of trust in accuracy and correctness of so called "sign-off" reports. This "sign-off test results"  or "not for sign-off test results" statement maybe an excuse for skipping a full review if the summary looks clean.

The automotive electronic device supplier must always verify in detail the report to clarify each reported non-conformance. Otherwise it may adversely affect the entire validation process through endless testing to fix potential false issues.

The sample of bad report shown below may easily go undetected by those searching for easy resolutions (pass / fail). 

In tis particular case two samples (7000 & 7002) are being evaluated for near filed interferences from portable transmitters.

The requirement for DUT in question is to pass Level 1 in band#9 (no deviation allowed under 7 Watts). The testing is carried out at 14 Watts, which is the Level 2 Severity. Whenever a deviation occurs the test operator must threshold the lowest severity level where the problem goes away.

Looking over page's date/time the scan below was generated before the scan above. However the order of pages is as was listed in the full report.

This kind of precision in measurements would humiliate any theory so far.

The perfect DUT type ever, perfect RI 115 equipment, perfect test operator, perfect identical hand portable transmitters immunity!

Going over pages's date/time they both have the same stamp. Theb why inserting them such that they apear to belong to separate test samples?

Surprisingly, but there is an antenna position where the result was either correctly tested or correctly represented.

This was the only instance where the RI 115 result from one sample was not copied over the for the other sample.

The RI 115 make up report saga continues. As long as the customer is preoccupied by the deviation in Level 1 it will never pay attention that only one sample was fully tested. The really bad part is that the designer will believe there is some sort of stability in DUT's behavior when in fact it was a huge instability.

Again same date/time stamp but different test sample numbers. How was this possible?

Christian Rosu

Trialon EMC Laboratory, Burton, MI

Igor Klivak

ES-XW7T-1A278-AC Immunity from Continuous Disturbances: CI 210

This test refers to continuous disturbances produced by vehicle’s charging system that can affect DUT functions.

• Level 2 requirements, as delineated in ES-XW7T-1A278-AC was removed in EMC-CS-2009.1, then added back in FMC1278.
• The frequency range allocated for severity levels was changed subsequently in all three Ford EMC specifications.
• The most significant differences for Us Vp-p requirements occurred between  ES-XW7T-1A278-AC & EMC-CS-2009.1.

• The test harness connecting the DUT to the Test Fixture and transient pulse generator shall be < 2000 mm in length.
• The DUT and wire harness shall be placed on an insulated support 50 mm above the ground plane. If the outer case of the DUT is metal and can be grounded when installed in the vehicle, the DUT shall be mounted and electrically connected to the ground plane.
  

1. Adjust DC offset of the signal generator/audio amplifier to 13.5 volts with the DUT disconnected (open circuit)
2. At each test frequency set and record the signal generator output to the specified voltage level with the DUT disconnected (open circuit).
3. Without the test signal present, connect the DUT and verify that it is functioning correctly.
4. Apply the test signal to the DUT and the Test Fixture such that all power and control circuits are exposed to the disturbance. All power and control circuits are tested simultaneously.
   

• The test harness connecting the DUT to the Load Simulator and modulated DC supply shall be < 2000 mm in length.
• All DUT power/power return circuits shall be connected together at the modulated power supply.
• Per previous versions of this requirement, a ground plane may be placed under the DUT and Load Simulator, but if used, the DUT and wire harness shall be placed on an insulated support 50mm above the ground  plane. Additionally, the negative connection of the modulated DC supply and case of the Load Simulator shall be referenced to the ground plane.
  

1. Without the DUT connected, adjust the DC voltage offset "Up" of the modulated power supply to 13.5 volts. Initially set the AC voltage amplitude "Us" to zero volts.
2. Connect and activate the DUT and verify it is functioning correctly. Verify that Up remains at 13.5 VDC. Adjust the supply as required to achieve this voltage level.
3. At each test frequency increase Us to the corresponding stress level while the DUT is operating. The dwell time shall be at least 2 seconds. A longer dwell time may be necessary if DUT function response times are expected to be longer. This information shall be documented in the EMC test plan.
   

• The test harness connecting the DUT to the Load Simulator and modulated DC supply shall be < 2000 mm in length.
• All DUT power/power return circuits shall be connected together at the modulated power supply.

1. Without the DUT connected, adjust the DC voltage offset "Up" of the modulated power supply to DUT’s system voltage (13.5, 27 volts). “Us” is initially set to zero volts.
2. At each test frequency adjust and record the signal generator output required to achieve the specified modulation voltage level “Us” with the DUT disconnected (open circuit). Use the frequency steps listed.
3. Without the modulation signal present (i.e. Us = 0 volts), connect the DUT and verify it is functioning correctly.
4. At each test frequency, apply the signal generator levels recorded in step (2) to the DUT and the Load Simulator such that all power and control circuits are exposed to the disturbance. The dwell time shall be at least 2 seconds. A longer dwell time may be necessary if DUT function response times are expected to be longer. This information shall be documented in the EMC test plan and test report.