Lake Shore Model 475 Gaussmeter User’s Manual
1-4
Introduction
Probe Availability:
Listed in Chapter 7 with specifications are some of the commonly used probes for the Model 475
gaussmeter. This is by no means the limit of what is offered. All probe physical configurations previously supplied with
the 450 gaussmeter are available for the Model 475. The model number for Model 475 probes is identical, except an “H”
has been added as the first character. Lake Shore prides itself on trying to satisfy every customer request for special
probes.
Hall Generators:
The Model 475 will operate with a discrete hall generator when a suitable probe is not available. Users
can program nominal sensitivity and serial number into a blank connector (HMCBL-6, ordered separately) to provide all
gaussmeter functions except field and temperature compensation. If no sensitivity information is available, the Model
475 reverts to resistance measurement.
1.1.4
Display and Interface Features
Display:
The Model 475 has a two line by 20 character vacuum fluorescent display with 9mm high characters. During
normal operation. the display is used to report field readings and give results of other features like max/min or relative.
The display can also be configured to show probe temperature or frequency. When setting instrument parameters, the
display gives the operator meaningful prompts and feedback to simplify operation. The operator can also control display
brightness.
Keypad:
The instrument has a 22 position keypad with individual key assigned to frequently used features. Menus are
reserved for less frequently used setup operations. The keypad can be locked out to prevent unintended changes of
instrument setup.
Alarm and Relay:
High and low alarms are included in the instrument. Alarm actuators include display annunciator,
audible beeper and two relays. The relays can also be controlled manually for other system needs.
Voltage Output 1:
The first voltage output gives access to amplified voltage signal directly from the probe. This voltage
is corrected for the nominal sensitivity of the probe and provides the widest bandwidth of the three voltage outputs. In
wideband AC mode, its signal can be viewed on an oscilloscope to observe the shape of AC fields. In peak mode the
output can be used to view pulse shape or other characteristic of a momentary signal. Output 1 serves only as a
diagnostic tool in DC and narrow band AC modes because the intrinsic modulation of the probe signal prevents a clear
view of the field response.
Voltage Output 2:
The second voltage output provides a voltage proportional to measured field with the benefits of
some signal processing. The output is produced by the DSP through a fast D/A converter. The output signal is updated at
40 kHz, giving good response for low to mid frequency fields. Signal quality degrades at high frequency because of the
sampling rate. Probe offset correction and correction for the nominal sensitivity of the probe can be performed on this
signal.
Voltage Output 3:
The third voltage output provides a voltage proportional to measured field with the most signal
processing of the three outputs. All probe compensation available to the display readings, including temperature
compensation, can be performed on this output. The output is produced by the microprocessor through a high-resolution,
16-bit, D/A converter updated at 30 readings per second. This output can also be used for field control.
Computer Interface:
Two computer interfaces are included with the Model 475, serial RS-232C and parallel IEEE-488.
Both allow setup of all instrument parameters and read-back of measured values. The reading rate over interface is
nominally 30 readings per second but ranges from 10 to 100 readings per second depending on setup. Lake Shore makes
LabView drivers available to its instrument users, consult factory for availability.
