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

Measurement Instrumentation Uncertainty – (RE, CE-V,CE-I) Automotive Electronic Components

3. April 2023 14:29 by Christian in EMC/EMI, Test Methods, Uncertainty
CISPR 25 Conducted Emissions - Current Method - MU Sources CISPR 25 Conducted Emissions - Voltage -

CISPR 25 Conducted Emissions - Current Method - MU Sources

CISPR 25 Conducted Emissions - Voltage - MU Sources 

CISPR 25 Radiated Emissions - ALSE Method - MU Sources

CISPR 25 RF EMISSIONS INPUT QUANTITIES - PROBABILITY DISTRIBUTION FUNCTION

CISPR 25:2021

Reporting Measurement Uncertainty in automotive electronics EMC

3. April 2023 11:14 by Christian in EMC/EMI, Uncertainty
Measurement Uncertainty Budget is not a requirement imposed by any of the automotive EMC specificati

 Measurement Uncertainty Budget is not a requirement imposed by any of the automotive EMC specifications and their approved report
templates. Not all international standards behind EMC Test Methods mention the Uncertainty Budget for outlined test equipment configuration.
The OEM EMC specs are asking the use of specific test equipment approved by them and in some instances designed by them.

 

Christian Rosu, 2023-04-02

Automotive OEM Requirement for EMC Test Method Measurement Uncertainty

3. April 2023 11:01 by Christian in EMC/EMI, EMC TEST PLAN, Uncertainty
Automotive EMC/Electrical testing specs like GM3097:2019, GMW3172:2022, FMC1278:2021, FMC1279:2021,

Automotive EMC/Electrical testing specs like GM3097:2019, GMW3172:2022, FMC1278:2021, FMC1279:2021, CS0054:2018,
VW80000:2021 do not mention Measurement Uncertainty as requirement for reports.

CISPR 25:2021 includes INFORMATIVE Measurement Uncertainty but this is not a requirement for CISPR 25 compliant reports.

4.1.5 Test report
The report shall contain the information agreed upon by the customer and the supplier, e.g.
• sample identification,
• date and time of test,
• bandwidth,
• step size,
• required test limit,
• ambient data and test data.
Annex L (informative) Measurement instrumentation uncertainty – Emissions from components/modules – Test methods.
Annex M (informative) Uncertainty budgets for emissions from components/modules.

ISO 7637-2:2021 - no reference to Measurement Uncertainty.
ISO 7637-3:2016 - no reference to Measurement Uncertainty.
ISO 16750-2:2012 - no reference to Measurement Uncertainty.
ISO 16750-1:2018 - no reference to Measurement Uncertainty.


ISO 11452-2:2019 - no reference to Measurement Uncertainty.
ISO 11452-4:2020 - no reference to Measurement Uncertainty.
ISO 11452-8:2015 - no reference to Measurement Uncertainty.
ISO 11452-9:2012 - no reference to Measurement Uncertainty.
1SO 10605:2008 - no reference to Measurement Uncertainty.

Measurement Uncertainty is not a requirement for automotive electronic standards, nor a requirement of the vehicle OEMs. Measurement
Uncertainty is already included in the test levels (e.g. RE Limit Lines or RI Severity Level) for the automotive standards. These the limits are not affected by the measurement uncertainty budget generated by the laboratory for each test.

In the Commercial Electronics world (FCC & CE Mark), the Measurement Uncertainty is included in the report. This is because these
Commercial Standards require that a certain measurement uncertainty be achieved in order to apply the specified limits. If the lab's
measurement uncertainty doesn't meet the minimum requirements, then the limits must be adjusted based upon the lab's measurement
uncertainty calculations. However, this is not the case in the Automotive Industry.

Christian Rosu (Apr 2, 2023)

Automotive OEM Requirement for EMC Test Method Measurement Uncertainty

3. April 2023 11:01 by Christian in EMC/EMI, EMC TEST PLAN, Uncertainty
Automotive EMC/Electrical testing specs like GM3097:2019, GMW3172:2022, FMC1278:2021, FMC1279:2021,

Automotive EMC/Electrical testing specs like GM3097:2019, GMW3172:2022, FMC1278:2021, FMC1279:2021, CS0054:2018,
VW80000:2021 do not mention Measurement Uncertainty as requirement for reports.

CISPR 25:2021 includes INFORMATIVE Measurement Uncertainty but this is not a requirement for CISPR 25 compliant reports.

4.1.5 Test report
The report shall contain the information agreed upon by the customer and the supplier, e.g.
• sample identification,
• date and time of test,
• bandwidth,
• step size,
• required test limit,
• ambient data and test data.
Annex L (informative) Measurement instrumentation uncertainty – Emissions from components/modules – Test methods.
Annex M (informative) Uncertainty budgets for emissions from components/modules.

ISO 7637-2:2021 - no reference to Measurement Uncertainty.
ISO 7637-3:2016 - no reference to Measurement Uncertainty.
ISO 16750-2:2012 - no reference to Measurement Uncertainty.
ISO 16750-1:2018 - no reference to Measurement Uncertainty.


ISO 11452-2:2019 - no reference to Measurement Uncertainty.
ISO 11452-4:2020 - no reference to Measurement Uncertainty.
ISO 11452-8:2015 - no reference to Measurement Uncertainty.
ISO 11452-9:2012 - no reference to Measurement Uncertainty.
1SO 10605:2008 - no reference to Measurement Uncertainty.

Measurement Uncertainty is not a requirement for automotive electronic standards, nor a requirement of the vehicle OEMs. Measurement
Uncertainty is already included in the test levels (e.g. RE Limit Lines or RI Severity Level) for the automotive standards. These the limits are not affected by the measurement uncertainty budget generated by the laboratory for each test.

In the Commercial Electronics world (FCC & CE Mark), the Measurement Uncertainty is included in the report. This is because these
Commercial Standards require that a certain measurement uncertainty be achieved in order to apply the specified limits. If the lab's
measurement uncertainty doesn't meet the minimum requirements, then the limits must be adjusted based upon the lab's measurement
uncertainty calculations. However, this is not the case in the Automotive Industry.

Christian Rosu (Apr 2, 2023)

Calibrating Filed Probes for Automotive EMC Standards

24. February 2020 09:31 by Christian in EMC/EMI, Test Methods, Calibrations, Uncertainty
IEEE 1309:2013 is the Standard for Calibration of Electromagnetic Field Sensors and Probes (Excludin

The accuracy of RF Field Level during ALSE RF Immunity per ISO 11452-2:2019 Substitution Method relies on the Field Probe calibration factors. An incorrect Field Probe Calibration may result in significant deviations from the field levels called by automotive OEM specs. The Field Probe Calibration Report provides correction factors that are introduced into RF Immunity Test Software (e.g. TILE, NEXIO). Using calibration factors acquired at 15 V/m instead of 300 V/m can force the RF Amplifier output to maximum w/o the Field Probe to report expected Field Level. Moving transmitting antenna 10 inches closer to the Field Probe would allow the probe to report the expected field level, however this level is in fact higher as consequence of using bad correction factors.

RF Field Probe Selection for EMC Testing

Calibration Factors: corrections are provided as dB adjustments & multiplication factors. Maximum field measurement accuracy is achieved when the detailed 3-axis calibration is applied.

     Probe Calibration Certificate

     A) filed level applied via calibration antenna (V/m)

     B) filed level reported by probe (V/m)

     C) calculated multiplier factor

          A = B * C (e.g. 100 V/m = 120 V/m x 0.8333 where 0.8333 is the correction factor)

Sensitivity/Dynamic Range: e.g. (0.5 – 800V/m for 0.5 MHz – 6 GHz)

Linearity: the measure of deviation from an ideal response over the dynamic range of the probe that may vary as a function of the applied field level. (e.g. ±0.5dB 0.5 – 800 V/m).

Overload: the field level where damage can occur to the probe (e.g. 1000 V/m CW).

Isotropic Deviation: the variation of the probe’s response from ideal as it is rotated in the field. The minimal isotropic deviation of spherical probes (±0.5dB 0.5 MHz – 2 GHz).

Response time: the time a probe takes to respond to an applied RF field (e.g. 20 ms).

Sample rate: the rate at which information can be retrieved from the probe (e.g. 50 samples/second). 

Probe Type: refers to the configuration of the probe sensors. 

 

  • An isotropic RF filed measures the total value of the field level and is unaffected by field polarity. This is accomplished by summing measurements from three different sensors placed orthogonal to each other. 
  • Non-isotropic probes measure fields in one polarity at a time for electric field or magnetic field. 

 

IEEE 1309:2013 is the Standard for Calibration of Electromagnetic Field Sensors and Probes (Excluding Antennas) from 9 kHz to 40 GHz. 

The EMC lab must inform the calibrator about critical requirements imposed by automotive specs/standards for proper field calibration factors:

 

  1. The frequency range or center frequencies as delineated by automotive OEM EMC specs (e.g CS.00054, GMW3097, FMC1278).
  2. The filed level for each frequency band (e.g. 80V/m, 100V/m, 200V/m, 300V/m)
  3. Field Probe orientation (all three axes X, Y, Z facing antenna).
  4. Use 1 meter antenna distance to Field Probe. This is not always possible, therefore using a lower distance in far field  (e.g. 30 cm) should be acceptable.
  5. Calibrate the probe using CW with transmitting antenna in both horizontal/vertical polarization.

 

IEEE 1309:2013 A.2.4.3 Field strength: if the probe or sensor linearity is better than ± 0.5 dB, the frequency response calibration of the probe can be performed at any field strength level, but preferably close to the field levels used in the EUT tests. It is also required that the same probe range and/or gain settings as used in the EUT tests are used in the probe calibrations.

IEEE 1309:2013 A.2.4.4 Linearity check for probe or sensor:

For applications needing multiple field strength calibrations, e.g., 3 V/m, 10 V/m, and 18 V/m, the linearity tests shall be performed for each level. Note that for automotive EMC testing the above e.g. translates to levels like 100V/m, 200V/m, 300V/m.

IEEE 1309:2013 A.2.4.5 Probe isotropic response

For isotropic probes using three orthogonal elements, it is recommended that the frequency response and linearity response measurements be performed for each axis individually. Each axis should be aligned with the incident field successively to provide a maximum response. Probe calibration in a single orientation, such as only the orientation used in a UFA calibration, is not recommended, because the transmitting antennas, separation distances, and the end-use environment are typically not the same between the two setups.

Example of RI ALSE Test Configuration
 
 
Example of Field Calibration using Field Probe Type A per FMC1278R3 

 
Example of Field Calibration using Field Probe Type B per FMC1278R3 
 

 
Example of Field Probe Specs (AR FP5082)
 

 
References: IEEE 1309:2013, ISO 11452-2, FMC1278 Rev3, 28401NDS02 [8], AR App Note #44
Christian Rosu, Feb 24, 2020
 

AR_App_Note_44_RF_Field_Probe_Selection.pdf (352.8KB)

Rhode & Schwarz Equipment Calibration Interval:

https://gloris.rohde-schwarz.com/anonymous/en/pages/toplevel/calibration-process.html