Lake Shore Model 421 User Manual
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Lake Shore Model 421 Gaussmeter User’s ManualHall Generator C-3C2.3 HANDLINGCAUTION: Care must be exercised when handling the Hall generator. The Hall generator isvery fragile. Stressing the Hall generator can alter its output. Any excess forcecan 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 producethe Hall Generator is very brittle. Use the leads to move the Hall generator. Do not handle thesubstrate. The strength of the lead-to-substrate bond is about 7 ounces, so avoid tension on the leadsand especially avoid bending them close to the substrate. The Hall Generator is also susceptible tobending and thermal stresses.C2.4 POLARITYIf the control current enters the red lead (with +IC connected to the positive terminal of the currentsupply), and the magnetic field direction is as shown in Figure C-2, a positive Hall voltage will begenerated at the blue lead (+V H). Reversing either the current or the magnetic field will reverse theoutput voltage.C2.5 LEAD CONFIGURATIONSAll Hall generators (except Models HGCA-3020 and HGCT-3020) have 34 AWG solid copper withpoly-nylon insulation and have the same lead configuration as follows:3-K 31K53-2 % 312%K ) OO ) % 2 The Model HGCA-3020 and HGCT-3020 Hall generators have 34 AWG stranded copper with Teflon ®insulation and have the following lead configuration:3-K 5 731K53-2 %N"312 %K ) OO ) % 2 C3.0 HALL GENERATOR GENERIC HOOKUPThe Hall voltage leads may also be connected directly to a readout instrument, such as a highimpedance 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. In this case, a separateprecision current source (Lake Shore Model 120CS or equivalent) is necessary. See Figure C-3.CAUTION: The four Hall generator leads connect to four points on a sheet of semiconductormaterial having different potentials. No two leads can be connected togetherwithout adversely affecting operation. Therefore, the current source and the outputindicator cannot have a common connection, but must be isolated from each other.One, the other, but not both, may be grounded.CAUTION: Do not exceed the maximum continuous control current given in the specifications.The Hall generator input is not isolated from its output. In fact, impedance levels on the order of theinput resistance are all that generally exist between the two ports. To prevent erroneous currentpaths, which can cause large error voltages, the current supply must be isolated from the outputdisplay or the down stream electronics. |
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