Reed switch
Videos
The reed switch is an electromechanical switch operated by an applied magnetic field. It was invented in 1922 by professor Valentin Kovalenkov at the Petrograd Electrotechnical University, and later e
(from top) Single-pole reed switch, four-pole reed switch and single-pole reed relay. Scale in centimeters.
A reed relay from a TXE-3 telephone exchange
PKM 1B (left) next to Cherry MX
Hall effect sensor
Videos
A Hall effect sensor is any sensor based on the Hall effect, in which a voltage is produced proportional to one axial component of the magnetic field vector B.
Reed switch
…or where corrosion would affect open switch contacts. 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…
Engine fan with Hall effect sensor
Hall effect current sensor with internal integrated circuit amplifier. 8 mm opening. Zero current output voltage is midway between the supply voltages that maintain a 4 to 8-volt differential. The non-zero current response is proportional to the voltage supplied and is linear to 60 amperes for this particular (25 A) device.
Diagram of Hall effect current transducer integrated into ferrite ring
Multiple 'turns' and corresponding transfer function