ETS-Lindgren 94456 Current Probe (Archived) - Manual (Page 13)

MODEL 94456 CURRENT PROBES Operation
© EMC TEST SYSTEMS, L.P. – MARCH 2002 9
REV B – PN 399265
OPERATION
The RF current probe is a broadband RF transformer for
use with EMI test equipment. Radio frequency currents can
be measured in cables without physically disturbing the
circuit.
SIGNAL MEASUREMENT
Oscilloscope Use – In terms of RF Amperes
1. Standardize the gain of the oscilloscope to read
correctly the voltage (E
S
) applied to its input terminals.
2. Divide E
S
in volts by the average current probe transfer
impedance Z
T
in Ohms. The result is the value of the
RF signal in terms of Amperes in the test conductor.
Example:
Assume an oscilloscope peak voltage measurement of 5
Volts and the average Z
T
to be 1.06 Ohms. Then: 5/1.06 =
4.71 Amperes in the test conductor. The example is valid
providing that the oscilloscope rise time (T = 0.3/BW) is
shorter than RF signal pulse duration. This also applies to
the current probe which has a rise time of about 3
nanoseconds based on a 100 megahertz bandwidth.
In Terms of dB Above One Microampere at Meter
Input (CW Conducted Measurements)
1. Adjust the EMI test equipment for standard gain and
make a measurement of the CW signal (voltage output
from the current probe) in terms of dB above one
Archived 6/1/10