Data Sheet

Closed-loop current measurement
Whereas the primary purpose of the I-prober 520 is as a positional current
probe, the are many circumstances where current measurements can be
made in the conventional way by
enclosing the conductor.
To increase its overall usefulness,
the I-prober 520 is supplied with
a clip-on toroid assembly which
converts it into a closed magnetic
circuit probe for measuring current
in a wire.
The toroid is open until the probe
is attached, allowing insertion of
the wire without disconnection.
The wide bandwidth, dynamic
range and low noise of the probe
are retained but higher accuracy,
repeatability and unwanted field
rejection are achieved.
Measurement of electromagnetic field
The very small size of the field sensor within the I-prober 520 gives it
some unique capabilities when used to measure magnetic fields.
The variation of
field with position
can be accurately
determined enabling
the precise source of
fields to be located
and their variation in
space measured.
A switch on the
control box re-scales
the output voltage to
measure in Teslas or
in amps per metre.
The I-prober 520 in use
The magnitude of the signal from a positional current probe is critically related
to its position relative to the conductor. The size of the conductor (e.g. the
width of a PCB track) also has a significant effect.
This means that the sensitivity of the I-prober has to be adjusted to match
the track width when quantitative measurements are required. A calibrator
within the control box enables sensitivity adjustment in conjunction with a
calibration graph.
The measurement result will also include other field effects present at the tip
of the probe and not just that coming from the current through the conductor.
This may include DC effects from adjacent magnetised components and from
the earths magnetic field, plus AC effects from transformers and other field
radiating sources.
Current in adjacent tracks, or tracks on
the opposite side of the PCB will also
affect the measurement.
There are solutions to these potential
problems. The unwanted DC can
be nulled out by observing the
measurement without power to the
circuit, whilst AC interference can be
attenuated using bandwidth filters. The
I-prober control box includes a wide
range DC offset control and switchable
filters.
Nevertheless, the use of the I-prober
520 requires interpretation based upon
a proper understanding of circuits and
systems. It is a tool for the professional
engineer.
Minimal circuit disturbance
With many high frequency switching circuits and high bandwidth signal
paths, inserting even a short loop of wire into the track path can change the
inductance sufficiently to alter the circuit performance.
Unlike a conventional current probe, the I-prober 520 has an extremely low
insertion impedance and negligible stray capacitance.
This enables current observations and measurements to be made without
disturbance to the circuit.
Safe for higher voltage use
The I-prober 520 is safety rated to 300V CAT 11
(600V CAT 1).
This enables it to be used on circuits with direct
connection to AC line at up to 300V rms, and on
isolated circuits at voltages up to 600V rms.
A finger guard is incorporated to maintain user
safety at higher voltages.
The probe can be used to measure high
temperature PCB tracks and component leads
up to 120
o
C continuous or 150
o
C short term.
Aim I-prober 520
- a innovative and flexible measurement tool