Lake Shore 420, Руководство пользователя

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Lake Shore Model 420 Gaussmeter User’s Manual
Accessories and Probes
6-5
6.2 PROBES
There are four types of Model 420 probes available: Transverse (Figure 6-8), Axial (Figure 6-9), Flexible
Transverse (Figure 6-10), and Gamma (Figure 6-11) - each named by its Hall sensor orientation. Because the
Model 420 covers such a wide magnetic field range (0.01 mG to 300 kG), three probe ranges are available:
High Stability (HST), High Sensitivity (HSE), and Ultra-High Sensitivity (UHS). Consult the factory for
availability of probe types not detailed in these figures.
Selecting the right probe can be difficult. Below are simple guidelines to help in the selection process.
1. Match the probe to the application. Do not buy more accuracy, field range, or fragility than necessary.
2. The thinner a probe, the more fragile it is. Avoid selecting an easily damaged probe based on a possible,
but not probable, future application. For instance, avoid using an exposed-device probe such as a Model
MFT-3E03 type for general field measurements. A damaged probe stem or sensor is irrepairable.
3. Metal enclosed probes, such as the Model MMT-6J08 and MMA-2508, offer the greatest Hall sensor
protection and are the most rugged.
4. Be cautious about aluminum stemmed, transverse probes like the Model MMT-6J08 types, if measuring
AC magnetic fields. Eddy currents in the aluminum can affect accuracy. A superior choice for AC
measurements is the Model MNT-4E04 type fiberglass-epoxy stem probes.
5. Each probe type has several stem lengths. User preferences or test set-up dimensions usually determine
final selection. Longer stems are more susceptible to accidental bending (mostly bothersome, not
catastrophic). Stem length does not affect performance.
6. Be aware of the differences in the probe “active areas” shown on the data sheet. A Hall effect probe
indicates the average field value sensed over that total active area. Thus, when measuring magnetic
fields with a high gradient across the sensor width, choose the smallest active area practical,
remembering guideline #2 above.
7. Lake Shore gaussmeter probes provide valid readings over different ranges of magnetic fields. Check the
specification sheet for these usable ranges. Use High Stability probes, (i.e. -VG models) on 300 gauss
(30 millitesla) to 30 kilogauss (3 tesla) full scale ranges. Use High Sensitivity probes (i.e., -VH models) on
30 G (3 mT) to 30 kG (3 T) full scale ranges. Use specially calibrated High Field probes for fields above
30 kG (3 T). Use the Gamma probe™ on the 300 mG (30 µT) and 3 G (300 µT) ranges.
8. If no standard probe configuration fits your needs, Lake Shore offers custom probes to meet physical,
temperature, and accuracy requirements. Contact Lake Shore for details.