DRAFT Recommended Practice for Measurements and ...

1/29/98 64 C95.3-1991 Revision — 2 nd Draft
10/98 Draft
through a suitable series resistance, to electrodes that contact the upper and lower
plates of the induced current meter. An RF current transformer is used to measure the
current applied to the induced current meter and the output of the transformer is
monitored using an RF voltmeter (Tell, 1995). (See Figure 4.8)
Fig. 4.8 Current Injection Method for Calibrating Stand-on Induced Current
Meters.
The clamp-on induced current meter is calibrated in a manner similar to that used for
common RF current transformers. A special fixture is used that connects to a 50 ohm
coaxial line and expands the outer shield to allow access to the inner center conductor
(similar in principle to a TEM cell). The size of the fixture must accommodate the larger
dimension of the clamp-on induced current meter when it is connected around the center
conductor of the test fixture. (See Figure 4.9.) An insulating spacer is often used to
center the conductor within the aperture of the induced current meter. RF power from a
suitable source is transmitted through the fixture to a termination with a means for
measuring total transmitted power, e.g., a feed-through termination. The current flowing
in the coaxial line and, hence, through the aperture of the induced current meter is
calculated using Ohm’s law.
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subject to change.