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EMC

CISPR 25:2016 / 2021 CEC Limits

Conducted Emission – Current Probe Method

This table summarizes the Conducted Emission (CEC) current probe method limits (corresponding to Table 6/7) for automotive components and modules per CISPR 25, including complete data for Class 1-5, suitable for EMC pre-compliance and certification reference.

Limit Visualization Curve
Class:
Filter Table by Class:
Levels in dB(µA). Scroll horizontally to view more.
Service / Band
Frequency MHz
Class 5 Class 4 Class 3 Class 2 Class 1
Peak QP Avg Peak QP Avg Peak QP Avg Peak QP Avg Peak QP Avg
BROADCAST
LW 0.15 to 0.30 50 37 30 60 47 40 70 57 50 80 67 60 90 77 70
MW 0.53 to 1.8 26 13 6 34 21 14 42 29 22 50 37 30 58 45 38
SW 5.9 to 6.2 19 6 -1 25 12 5 31 18 11 37 24 17 43 30 23
FM 76 to 108 4 -9 -16 10 -3 -10 16 3 -4 22 9 2 28 15 8
TV Band I 41 to 88 0 - -10 6 - -4 12 - 2 18 - 8 24 - 14
DAB III 171 to 245 -2 - -12 4 - -6 10 - 0 16 - 6 22 - 12
MOBILE SERVICES
CB 26 to 28 10 -3 -10 16 3 -4 22 9 2 28 15 8 34 21 14
VHF 30 to 54 10 -3 -10 16 3 -4 22 9 2 28 15 8 34 21 14
VHF 68 to 87 4 -9 -16 10 1 -10 16 7 -4 22 13 2 28 15 8
VHF 142 to 175 4 -9 -16 10 1 -10 16 7 -4 22 13 2 28 15 8

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Test Setup & Technical Overview

Detailed engineering guide for Conducted Emissions (CEC) by Current Probe Method

Technical Overview: CEC vs LISN

The Current Probe Method (CEC) and the LISN Voltage Method (CEV) are the two primary approaches for evaluating conducted emissions on automotive component power lines and signal harnesses.

While the LISN method measures RF noise voltage across a nominal 50 Ω impedance network directly connected to the power lines, the CEC method utilizes a specialized current clamp to measure the noise currents flowing through the entire wiring harness without physically breaking the circuits.

The current probe method is exceptionally effective for detecting RF current loops that can lead to cable radiation at high frequencies, serving as a critical indicator for potential radiated emission failures.

Test Configuration & Setup Details

Proper physical setup is paramount to ensure reproducibility. Under CISPR 25, the Equipment Under Test (EUT) is positioned on a non-conductive, low-dielectric support 50 mm above the ground plane (GP).

The ground plane itself must be a copper or galvanized steel sheet (minimum 0.5 mm thick) bonded securely to the shielded enclosure. The wiring harness should be 1700 - 2000 mm in length and routed parallel to the edge of the ground plane.

To capture standing wave resonances, current measurements are taken with the probe positioned at two distinct locations along the harness: 50 mm from the EUT connector (targeting high-frequency emissions) and 750 mm from the connector (targeting mid-to-low-frequency resonances).

Interpretation of Limits (Class 1-5)

CISPR 25 specifies five limit classes to accommodate different vehicle environments and installation configurations:

  • Class 5: The most stringent class, typically mandated by OEMs for safety-critical components (ADAS, steering, braking) or devices located near sensitive radio antennas.
  • Class 4 & 3: Applied to standard body electronics, powertrain control units, and infotainment displays.
  • Class 2 & 1: The least severe limits, reserved for simple, transient, or non-critical loads (e.g., seat adjusters, window motors) that present minimal risk to the vehicle's RF receivers.

How to read the CISPR 25 CEC reference

User task

Use CEC to inspect RF current on the vehicle harness with the current-probe method. Class 1–5 rows, edition selection and probe-position context are kept visible so a current result is not mistaken for a LISN voltage result.

Choose before comparing

Select the 2016 or 2021 edition before comparing a class row. The cited 2016 reference context reaches 150 kHz–2500 MHz and the 2021 context reaches 150 kHz–5925 MHz; the visible rows are selected service bands rather than a continuous sweep. The current-probe result is expressed in dBµA; the receiver band and RBW, including the 9 kHz entries shown for the 2021 data, belong to the selected edition and test plan. No radiated-test distance applies.

What the displayed rows mean

Method and unit
CEC is the conducted-emission current-probe method and uses dBµA, not the dBµV voltage unit used by CEV.
Edition and RBW
The cited 2016 reference context reaches 150 kHz–2500 MHz and the 2021 context reaches 150 kHz–5925 MHz; the visible rows are selected service bands, not a continuous sweep. They are separate data sets; the selected 2021 rows expose 9 kHz RBW where encoded and must not be silently mixed with 2016.
Harness position
Probe placement along the harness, including the 50 mm and 750 mm positions used by this reference, is part of the comparison; no antenna distance is involved.

Common misread

CEC current limits cannot be compared numerically with CEV voltage limits just because both are conducted methods. Keep probe calibration, harness position, edition, detector and RBW with the result.

Reference boundary

EMCCalc summarizes the public IEC Webstore records for CISPR 25:2016 and 2021 and the encoded table data. The purchased edition and the agreed vehicle test plan remain authoritative; standard text is not reproduced here.

Content review date:

Source and verification

Primary source

IEC Webstore — CISPR 25:2016 Edition 4.0; 2016 table set

IEC Webstore — CISPR 25:2021 Edition 5.0; 2021 table set and RBW values

Applicability
Vehicle electronic/electrical components and modules for protection of on-board receivers; Class 1–5 data are selectable.
Read this limit with
  • Current-probe method on the harness
  • dBµA
  • Receiver bands and RBW are shown for the selected edition where encoded
  • Harness, probe position, artificial network, and detector settings must follow the selected edition and test plan
  • No radiated-test distance applies
Last source-link and context review
Verification method
The source link, edition/section locator, and measurement context were reviewed against the values shown here. This reference is not a formal conformity assessment or certification.

Engineering reading

Choose the applicable vehicle/component scope, standard edition, class, method, receiver setting, and full test plan before using this lookup for a compliance decision.