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Atlas Compliance & Engineering, Inc.
1792 Little Orchard Street
San Jose, CA 95125
Phone 408.971.9743
Fax 408-971-9783
Web www.atlasce.com
Conducted Emission Testing
For the conducted emissions testing, the EMCO LISN, Model No. 3825/2, was
used for the EUT and the EMCO LISN, Model No. 4825/2, was used for the support
equipment. During conducted emission testing the EUT was located on a wooden test
bench measuring 0.8 meter high, 1 meter deep, and 1.5 meters in width. The vertical
conducting surface was 0.4 meter from the back of the test bench. The LISNs were
placed on the ground plane of the test area in accordance with ANSI C63.4-2014.
The metal plane used for conducted emission testing was grounded to the earth by
a heavy gage braided wire attached to the plane. All other objects were kept a minimum
of 1 meter away from the EUT during the conducted test.
For conducted emissions testing a scan of the frequency band 150 kHz to 30 MHz
was made stepping every 5 kHz. Each frequency was measured at a bandwidth of 10 kHz
for 20 msec. Due to the narrow specification of a 6 dB drop, the 10 kHz bandwidth
meets the requirements of CISPR 16, band B (150 kHz to 30 MHz) and VDE 0876 as
well as of various military standards that require tolerances of 10% for a 10 kHz
measurement bandwidth. All readings within 25 dB of the limits were recorded, and
those emissions were then measured using the CISPR quasi-peak detector at a bandwidth
of 10 kHz for a 2 second measurement time. All emissions within 6 dB of the limit were
examined with additional measurements to ensure compliance with the stated limits.
Temperature and Humidity
The ambient temperature of the actual EUT was within the range of 10
to 40
C
(50
to 104
F) unless the particular equipment requirements specify testing over a
different temperature range. The humidity levels were within the range of 10% to 90%
relative humidity unless the EUT operating requirements call for a different level.
Sample Calculations
An example of how the EMI Test Receiver reading is converted using correction
factors is given for the emissions recorded in Table 8 and 10. These correction factors are
programmed into the EMI Test Receiver and verified. For radiated emissions in dB
V/m,
the EMI Test Receiver reading in dB
V is corrected by using the following formula:
Meter Reading (dB
V)
+ Antenna Factor (dB)
+ Cable Loss (dB)
- Pre-amplifier Gain (dB)
= Corrected Reading (dB
V/m)
This reading is then compared to the applicable specification limits and the
difference will determine compliance. For conducted emissions, the correction factors of
insertion loss are added for the 50
H/50 Ohm LISN used. These correction factors are
programmed into the EMI Test Receiver and verified.
