ETS-Lindgren 94606-6 Current Probe - Manual (Page 42)

42 | Operation
Signal Measurement
O SCILLOSCOPE U SE : I N T ERMS OF RF A MPERES
1. Standardize the gain of the oscilloscope to correctly read the
voltage (E
S ) applied to the 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.
I N T ERMS OF dB A BOVE O NE M ICROAMPERE AT M ETER I NPUT
(CW C ONDUCTED M EASUREMENTS )
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 microvolt. Use procedures outlined in the
EMI test equipment instruction manual.
2. Subtract the transfer impedance of the current probe in dB at the test
frequency from the dB measurement of the previous step. The result is
the value of the conducted CW signal in terms of dB above one
microamp at meter input.
At meter input as used in the MIL-I-26600 and MIL-I-6181D
specifications refers to the current in the test sample lead.