Lake Shore Model 475 Gaussmeter User’s Manual
Probes and Accessories
7-7
7.5
HALL GENERATOR
Lake Shore sells a series of bare Hall generators for applications that are unsuitable for standard probe configurations.
This section describes the handling, wiring and specifications of the bare Hall generators available from Lake Shore.
Please consult the factory for availability of bare Hall generator types not detailed in this section.
7.5.1
Hall Generator Handling
CAUTION:
Care must be exercised when handling the Hall generator. The device is very fragile. Stressing the Hall
sensor can alter its output. Any excess force can easily break the Hall generator. Broken Hall
generators are not repairable.
Hall Generators are very fragile and require delicate handling. The ceramic substrate used to produce the Hall sensor is
very brittle. Use the leads to move the Hall generator. Do not handle the substrate. The strength of the lead-to-substrate
bond is about 7 ounces, so avoid tension on the leads and especially avoid bending them close to the substrate. The Hall
Generator is also susceptible to bending and thermal stresses.
7.5.2
Hall Generator Lead Wires
Lake Shore Hall generators (except Models HGCA-3020 and HGCT-3020) have 34 AWG solid copper lead wire with
poly-nylon insulation and have the following color coded lead configuration.
The Model HGCA-3020 and HGCT-3020 Hall generators have 34 AWG stranded copper lead wire with Teflon
®
insulation and have the following color coded lead configuration:
7.5.3
Using a Hall Generator with the Model 475
Connecting a Hall generator to the Model 475 requires a Lake Shore Model HMCBL-6 or -20 Cable Assembly (sold
separately). The cable has a 15 pin D-sub connector on one end and four leads on the other. The 4 leads, illustrated in
Figure 7-9, correspond to the 4 leads on the Hall generators given in Paragraph 7.5.2.
Each Hall generator purchased from Lake Shore will come with a nominal field sensitivity value. However, we
recommend that the customer always check accuracy against a reference field rather than use the sensitivity value sent
with the bare Hall generator. Because Lake Shore has no control of the conditions beyond the cable, the customer must
accept responsibility for accuracy and compatibility.
In cryogenic applications, Manganin lead wire is frequently used because of its thermal conductivity properties.
Manganin wire is not usually acceptable for connection to a Hall generator because the resistance of Manganin wire is
often too high. The gaussmeter current source is limited in compliance voltage. The Model 475 should not drive a load
(Hall generator, wires in cryostat, and probe cable) greater than 50
Ω
. In fact, for best performance, the load should be
less than 30
Ω
. In cryogenic applications, Hall generators are normally connected using twisted pairs of copper wire such
as 34 gauge, Teflon insulated.
