Potentiometer#Rheostat

A rheostat is a continuously variable electrical resistor for high electrical power and / or high precision and stability ( temperature stability, long-term stability, good contact ).

The principle of the rheostat was invented in 1840 by Charles Wheatstone. It consists of a cylindrical ring made of non-conductive material, usually ceramic, around which a resistance wire, for example made ​​of constantan, is wound. A metal contact, which is moved over the resistance wire, the desired resistance can be adjusted, without interrupting the circuit.

Levels resistors have the rotary switch, the uninterruptible unlock usually 10 identical individual resistances in succession, see also resistance decade.

The Stöpselrheostat is another way to change resistors without interruption, but also in stages. With him partial resistances of resistor string are shorted with conductive plugs.

Similar Rheostat or stages starting resistors resistors were built to gently drive electric machines or trams. Because they lead to efficiency losses, you meet them today in this application no longer.

Rheostats are still used in electrical laboratories, among other things as an adjustable electrical loads.

Especially in the Anglo-Saxon parlance, the term is used for wire-wound potentiometer. Wirewound can now be found more often, they have a relatively small size. Examples are Entbrummer in tube amplifiers, potentiometer, in which the contact of a double helix of resistance wire runs are more consistently ( more than one turn from the start to the end of the resistor ) and are sometimes referred to as an input device (for example, pulse width, frequency) used in laboratory equipment. Another related application are angle encoder (see encoders or potentiometric ).