| Using a hall generator |
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| A Hall generator is a 4-lead device. The control current (IC) leads are normally attached to a current source such as the Lake Shore Model 120CS. The Model 120CS provides several fixed current values compatible with carious Hall generators. |
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Caution: Do not exceed the maximum continuous control current given in the specifications.
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The Hall voltage leads may be connected directly to a readout instrument, such as a high impedance voltmeter, or can be attached to electronic circuitry for amplification or conditioning. Device signal levels will be in the range of microvolts to hundreds of millivolts.
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The Hall generator input is not isolated from its output. In fact, impedance levels on the order of the input resistance are all that generally exist between the two ports. To prevent erroneous current paths, which can cause large error voltages, the current supply must be isolated from the output display or the down stream electronics.
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| Attaching discrete hall generators to Lake Shore gaussmeters |
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| Lake Shore provides cable assemblies containing the necessary electronic memory (EEPROM) to interface a Hall generator to a gaussmeter. This allows users to assemble a Hall sensor into a difficult to access area prior to gaussmeter attachment. The figure below shows the general cable configuration. While convenient, this method provides less than optimum performance. Because of the intricacies involved with proper calibration, the user is responsible for the measurement accuracy. A probe fully calibrated by Lake Shore is always suggested. Special probe mechanical configurations are also available. |
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| Certain Hall generator sensitivity constraints are applicable: |
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Sensitivities between 5.5 and 10.5 mV/kG at 100 mA control current. |
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Sensitivities between 0.55 and 1.05 mV/kG at 100 mA control current. |
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| Certain Hall generator sensitivity constraints are applicable: |
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For the Model 460, 450, and 421 Gaussmeters |
1.8 m (6 ft) and 6.1 m (20 ft) cables are available. |
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The cable is shipped with a disk containing the small program “Hallcal.exe,” which is used to transfer the Hall generator single-point sensitivity data to the cable EEPROM through the gaussmeter serial port. This program must be installed on an IBM PC compatible computer. (A null modem cable or adapter is required).
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For the Model 475, 455, and 425 Gaussmeters |
1.8 m (6 ft) and 6.1 m (20 ft) cables are available. |
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| Models 475, 455, and 425 offer the convenience of front panel programming. No external computer is required. The Hall generator serial number and single-point sensitivity are directly entered using the keypad. |
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