Lake Shore Model 420 Gaussmeter User’s Manual
3-6
Operation
45°
45°
Flexible Transverse Probe
Maximum Bend Angle
Do not bend from
tip of probe
Stem
Figure 3-3 Maximum Flexible Probe Bend Radius
3.12.3 Probe
Operation
NOTE:
For best results, allow the instrument and probe to warm up
for at least 5 minutes before zeroing the probe, and at least 30
minutes for rated accuracy. The probe and the zero gauss
chamber should be at the same temperature.
In the DC mode of operation, probe orientation affects the polarity
reading of the gaussmeter. On a transverse probe, the Lake Shore
name printed on the handle indicates the side for positive (+) flux
entry. On an axial probe, positive (+) flux entry is always from the
front of the probe. See Figure 3-4.
If the magnetic field orientation is unknown, determine it by turning
on
Max Hold
and slowly adjusting the probe. As the probe turns
and the measured field rises and falls, its maximum value is held
on the display. Note probe orientation at the maximum reading to
identify the field orientation.
3.12.4 Probe Accuracy Considerations
NOTE:
For best results, allow the instrument and probe to warm up for at least 5 minutes before zeroing the
probe, and at least 30 minutes for rated accuracy. The probe and the zero gauss chamber should be at the
same temperature.
Several element impact probe accuracy. Zero the probe before making critical measurements. The zero
probe function cancels out the zero offset of the probe or small magnetic fields. It is normally used with the
zero gauss chamber, but may be used with a non-shielded probe (registering the local earth magnetic field).
To cancel out large magnetic fields, use the Relative function (see Paragraph 3.8).
Probe temperature can also affect readings. Read the probe specification sheets to determine possible
temperature effects. To help offset the effects of temperature on the Hall sensor, a thermistor may be
included in the Lake Shore High Sensitivity and Ultra-High Sensitivity Probes. The High Stability Probe
requires no temperature correction due to inherent thermal stability of materials used in its construction.
Probe readings depend on the angle of the sensor (Hall sensor) in relation to the magnetic field. Maximum
output occurs when the flux vector is perpendicular to the plane of the sensor. This is the condition that exists
during factory calibration. The greater the deviation from right angles in either of three axes, the larger the
reading error. For example, a 5° variance on any one axis causes a 0.4% error, a 10° variance induces a
1.5% error, etc. See Figure 3-5.
N
S
Transverse Probe Orientation
For Positive (+) Measurement
Axial Probe Orientation
For Positive (+) Measurement
N
S
The Lake Shore Logo
Towards North Pole
Figure 3-4 Probe Orientation
for Positive Measurement
Summary of Contents for 420
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