Stray magnetic fields

A toroid is best for this application because it produces very little stray magnetic fields. 

A perpendicular approach with the magnet parallel to the reed switch gives one operation at max. operation distance (Fig. 5.7). This method of operation offers medium sensitivity to stray magnetic fields, large switching courses and hysteresis and high switching position tolerance. 

An angular motion which requires a large angle of movement to operate the switch (Fig. 5.10). This offers a medium sensitivity to stray magnetic fields and shorter switching distances than method A. 

Using a ring magnet with an axial motion, three closures can be obtained (Fig. 5.11). This method offers short switching distances and low sensitivity to stray magnetic fields. If a single operation is required, a very accurate adjustment is necessary. 

This method operates the switch with a rotating magnet. The magnet can either be parallel or perpendicular to the switch (Fig. 5.13). These methods offer very low sensitivity to stray magnetic fields and easy adjustment if a precise switching is not crucial to the operation. 

Anomalies in the power wiring are a common cause of stray magnetic fields in commercial buildings and hospitals. Neutral-to-ground connections downstream of the main bonding connection cause some of the neutral current to return via the ground path. This path is not predictable and results in residual magnetic fields due to mismatch in the supply and return currents to the various electrical circuits in the... 

There are several factors that have made SQUID magnetometers less attractive than other methods for NQR explosives detection. The SQUID magnetometers used for NQR detection were cooled to 4.2K for operation, as were the flux transformers. SQUIDs are generally broadband devices and must be shielded from stray magnetic fields. Optimal performance is obtained at low frequency, with sensitivity decreasing with increasing frequency. 

Magnetic methods can work similarly to the optical shutter method. A magnetic-field sensor is placed opposite a permanent magnet. With metal teeth on an encoded metal disc, it is possible to shield the magnetic field from the magnetic-field sensor. This kind of sensor is less precise than the optical shutter type because of the stray magnetic field, which has to be taken into account. A product... 

High surface sensitivity makes the technique vulnerable to contamination, necessitating the use of UHV procedures. The low energy of the emitted electrons makes the technique vulnerable to the presence of stray magnetic fields and so magnetic shielding may be required. 

The low energies of the electrons involved means that the technique can be vulnerable to stray magnetic fields and magnetic shielding may be required. Spectra can be influenced by the particular crystal structure of the sample s top few atomic layers, which may not be completely representative of the bulk material. IPES is generally not suitable for insulating materials. 

Electrostatic electron focusing is susceptible to the presence of stray magnetic fields and so magnetic shielding may be necessary. 

Until recently, all SEMs used a "pinhole objective lens and single SE detector located below the lens, as shown in fig. 6(a). A characteristic of the "pinhole" lens, in which the polepiece bore diameter closest to the specimen is smaller than the other bore, is that the stray magnetic field below the lens is very low. With the specimen in field-free space, the low energy SEs are readily collected by a SE detector located in the vicinity of the specimen. The other reason for selecting this particular lens design... 

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