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A reed switch has very low resistance when closed, typically as low as 0.05 ohms, whereas the Hall effect sensors can be in the hundreds of ohms. A reed switch requires only two wires whereas most solid-state devices require three wires. A reed switch can be said to require zero power to operate it.
These switches control which reed ranks are enabled (opened up) or disabled (closed off): some switches enable a single reed rank, others enable several simultaneous reed ranks. In general, the formula for the number of potential switch combinations is one less than 2 to the number of unique reed blocks that are within the accordion.
(from top) Single-pole reed switch, four-pole reed switch and single-pole reed relay. Scale in centimeters. A reed relay [i] is a type of relay that uses an electromagnet to control one or more reed switches. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them.
Angle–sensitive pixel; Colorimeter; Contact image sensor; Electro-optical sensor; Flame detector; Infra-red sensor; Kinetic inductance detector; LED as light sensor; Light-addressable potentiometric sensor; Nichols radiometer; Fiber optic sensors; Optical position sensor; Thermopile laser sensors; Photodetector; Photodiode; Photomultiplier ...
Hall effect devices produce a very low signal level and thus require amplification. The vacuum tube amplifier technology available in the first half of the 20th century was too large, expensive, and power-consuming for everyday Hall effect sensor applications, which were limited to laboratory instruments.
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The principle behind magnetic, mechanical, cable, and other float level sensors often involves the opening or closing of a mechanical switch, either through direct contact with the switch, or magnetic operation of a reed. In other instances, such as magnetostrictive sensors, continuous monitoring is possible using a float principle.
Switches can be designed to respond to any type of mechanical stimulus: for example, vibration (the trembler switch), tilt, air pressure, fluid level (a float switch), the turning of a key , linear or rotary movement (a limit switch or microswitch), or presence of a magnetic field (the reed switch). Many switches are operated automatically by ...