Lake Shore Model 475 Gaussmeter User’s Manual
7-2
Probes and Accessories
7.3
LAKE SHORE STANDARD PROBES
There are several types of Lake Shore Model 475 probes available: Axial, Gamma, Tangential, and Transverse —
generally named for the Hall sensor orientation. Because the Model 475 covers such a wide magnetic field range
(0.01 mG to 350 kG), three probe ranges are available: High Stability (HST), High Sensitivity (HSE), and Ultra-High
Sensitivity (UHS). Please consult the factory for availability of probe types not detailed in this section.
7.3.1
Hall Probe Selection Criteria
Proper selection of a Hall probe is probably the most difficult, and important, decision to make after choosing the
Model 475. Utilizing the wrong probe may lead to less than optimal accuracy or, even worse, costly damage.
Probe Application
Field measurement application is the controlling factor in probe selection. Application dictates the physical manifestation
of the measured field, including the parameters described briefly below along with relevant probe characteristics.
Magnitude:
Typical Hall probes cover an operating range of four to five orders of field magnitude. Operation beyond
this range often requires some compromise in performance, which is often higher noise or loss of resolution. Choosing
the correct probe type ensures optimal performance in the desired measurement range.
High Sensitivity (HSE):
High sensitivity probes are the most common for general-purpose field measurement. They
operate effectively in fields up to 35 kG (3.5 T) with excellent sensitivity over their entire
range. At low fields, their sensitivity can be as low as 5 mG (0.5
µ
T). HSE probes have a
relatively small active area making them convenient for many applications and they are
offered in a variety of stem geometries for convenience.
High Stability (HST):
With a high field range of up to 350 kG (35 T), high stability probes are used when fields
exceed the 35 kG (3.5 T) limit of HSE probes. Their low field performance is slightly
degraded with minimum sensitivity of 50 mG (5
µ
T). High stability probes are also
inherently more temperature stable than other probes and should be used when large
temperature excursions are expected. The same probe geometries are available for both
HST and HSE probes. HST probes are not to be used at frequencies above 800 Hz.
Ultra High Sensitivity (UHS):
Low magnitude, large volume fields are most effectively measured with ultra high
sensitivity probes that have unbeatable low field resolution to 20
µ
G (2 nT). UHS probes,
or gamma probes, are ideal for measuring fringe fields or variations in Earth’s magnetic
field. They should never be used in fields over 30 G. UHS probes are larger than other
probes and they have a very large active area, making them impractical for small volume
fields or tight spaces.
Orientation:
Getting to the field is often much of the challenge in selecting a probe. Field orientation dictates the most
basic probe geometry choice of transverse verses axial. Other variations are also available for less common, more
challenging applications. Listed below are the standard configurations for HSE and HST probes, USH probes require
special packaging that is not described here.
Transverse:
Transverse probes, most often rectangular in shape, measure fields normal to their stem width. They
are useful for most general-purpose field measurements and are essential for work in magnet gaps.
Several stem lengths and thicknesses are available as standard probes.
Axial:
Axial probes, most often round, measure fields normal to their end. They can also be used for
general-purpose measurements but are most commonly used to measure fields produced by
solenoids. Several stem lengths and diameters are available as standard probes.
Flexible:
Flexible probes are special because they have a flexible portion in the middle of their stem.
The active area at the tip remains rigid and somewhat exposed. (Flexible transverse probes are
significantly more fragile than other transverse probes.) Flexible probes should only be select for
applications that do not have direct access to the measured field with standard transverse or axial
probes.
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