Table of Contents
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1: Introduction
HAPTER
1.1.2 DC Measurement
Mode
1.1.3 AC Measurement
Mode
1.2 Measurement
Features
1.3 Instrument
Probe Features
1.3.1 Probe Field
Compensation
1.3.2 Probe Information
1.3.3 The Probe
Connection
Model 425 Gaussmeter
Static or slowly changing fields are measured in DC mode. In this mode, the
Model 425 uses probe field compensation to correct for probe nonlinearities, result-
ing in a DC accuracy to ±0.20%. Measurement resolution is enhanced with internal
filtering, allowing resolution to 4¾ digits with reading rates to 30 readings per sec-
ond over the USB interface.
In addition to the DC measurement mode, the Model 425 offers an AC measurement
mode for measuring periodic AC fields. The instrument provides an overall frequency
range of 10 Hz to 10 kHz and is equipped with both narrow and wide band frequency
modes. While in narrow band mode, frequencies above 400 Hz are filtered out for
improved measurement performance.
The Model 425 offers a variety of features to enhance the usability and convenience
of the gaussmeter.
Autorange: in addition to manual range selection, the instrument automatically
chooses an appropriate range for the measured field. Autorange works in DC and AC
measurement modes.
Probe zero: allows you to zero all ranges while in DC mode with the simple push
of a key.
Display units: field magnitude can be displayed in units of G, T, Oe, and A/m with
resistance in ).
Max hold: the instrument stores and displays the captured maximum DC or AC
field reading.
Relative reading: the relative mode calculates the difference between a live reading
and the relative setpoint to highlight deviation from a known field point. This feature
can be used in DC or AC measurement modes.
Instrument calibration: Lake Shore recommends an annual recalibration schedule
for all precision gaussmeters. Recalibrations are always available from Lake Shore,
but the Model 425 allows you to field calibrate the instrument if necessary. Recalibra-
tion requires a computer interface and precision low resistance standards of known
value.
The Model 425 offers the best measurement performance when used along with
Lake Shore Hall probes. Firmware-based features work in tandem with the probe's
calibration and programming to ensure accurate, repeatable measurements and
ease of setup. Many of the features require probe characteristics that are stored in the
probe connector's non-volatile memory.
The Hall effect devices used in gaussmeter probes produce a near linear response in
the presence of a magnetic field. The small nonlinearities present in each individual
device can be measured and subtracted from the field reading. Model 425 probes are
calibrated in a way to provide the most accurate DC readings.
The gaussmeter reads the probe information on power up or any time the probe is
changed to allow hot swapping of probes. Critical probe information can be viewed
on the front panel and read over the computer interface to ensure proper system con-
figuration.
The Model 425 is only half the magnetic measurement equation. For the complete
solution, Lake Shore offers a full complement of standard and custom Hall effect
probes in a variety of sizes and sensitivities. One of ten standard Hall probes is
included with the Model 425. Refer to page 5 for details on the Hall probes you can
choose to receive with the Model 425.
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