Irish Narrow Gauge - Contractors and Suppliers |
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Another well-known motor meter, working on a somewhat similar principle, is that of Chamberlain and Hookham. In its improved form this meter consists of a single horseshoe permanent magnet formed of tungsten-steel having a strong and constant field. Two air-gaps are made in this field parallel to each other. In one of these a copper disk, called the brake disk, revolves, and in the other a copper armature disk. The latter is slit radially, and the magnetic field is so arranged that it perforates each half of the disk in opposite directions. The armature is immersed in a shallow vessel filled with mercury, which is insulated from the vessel and the armature, except at the ends of the copper strips. The current to be measured passes transversely across the disk and causes it to revolve in the magnetic field; at the same time the copper brake, geared on the same shaft, revolves in the field and has local or eddy currents produced in it which retard its action. The principle of the meter is to make the breaking and driving action so strong that the friction of the train becomes immaterial in comparison. This meter is an ampere-hour meter and applicable only to continuous current circuits.
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i3@rrmail.com | 2002.07.27 |