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INSTRUCTION MANUAL
SECT IO N 6
-
TEST LEVEL CALIBRATION
Rev050321
Prior to the start of the calibration process,
U
mr
must be calculated.
U
mr
represents the voltage to be measured at the output of the
150Ω to 50Ω
Adapter connected to the EUT port of the EM Clamp; and must not be
confused with the
open circuit test level
(
U
o
) for the calibration (i.e.: 1 Vrms,
3 Vrms, 10 Vrms, etc., as specified in Table 1 of IEC 61000-4-6). The
relationship between
U
mr
and
U
o
for EM Clamp calibration is given in
NOTE:
The 6:1 ratio, or factor of 6
(15.6 dB)
is due to the following:
a)
the open circuit voltage is double the matched load
voltage, yielding a
2:1
voltage ratio; and,
b)
the EUT port of the EM Clamp is terminated by 150 ohms
(
150Ω to 50Ω Adapter
(
100 ohms) in series with the 50 ohm
input impedance of the measuring instrument). So, the
measurement is made across one-third of the total load
impedance, yielding a
3:1
voltage ratio.
So, for instance, for calibration performed at an
open circuit
test level
(
U
o
)
of
10 Vrms
:
Distributed by: Reliant EMC LLC, +1 408 916
‐
5750, [email protected], www.reliantemc.com
