Service Information
12
P6021 Instruction Manual
Circuit Description
This section describes the circuits in the P6021 current probe and termination.
For the schematic diagram of the probe and termination, see Figure 5 on page 13.
The P6021 current probe consists of a current transformer mounted in the nose of
the probe head case, an impedance-matching network, and an internal switch to
disconnect the transformer shield from ground.
The transformer contains a two-section U-shaped ferrite core. One section is
stationary; the other is mechanically movable to permit closing the core around
the conductor being measured. The conductor under test forms a one-turn
primary winding for the transformer; the windings around the stationary portion
of the core are the secondary windings. Paralleled windings in the secondary
assure a fast step response. The circuitry between the transformer and the coaxial
cable corrects any differences in level between the signal induced in the parallel
windings of the secondary and matches the balanced probe winding to the cable.
As indicated on the probe body, the turns ratio of the P6021 is 125:1. This refers
to the number of windings in the secondary of the probe transformer.
The probe transformer is shielded to eliminate interference from outside signals.
To eliminate the possibility of creating a short circuit from this shield to the
conductor being measured, the slide switch disconnects the ground from the
shield when you open the sliding portion of the probe to connect or remove it
from a conductor.
The P6021 termination consists of a 62.5
W
impedance-matching network to
terminate the coaxial cable and a voltage divider that is switched in by a
sensitivity control to change the sensitivity by a factor of five. When the control
is in the 2 mA/mV position, a 10 mA current signal in the conductor under test
induces a 5 mV signal at the output of the termination. (This assumes that the
termination is connected to a 1 M
W
input oscilloscope.)
When the sensitivity control is in the 10 mA/mV position, a 10 mA current
signal is attenuated to induce a 1 mV signal at the output of the termination.
Current Probe
Termination
To Next Page
Loading...
Need help?
General
