Variable Resistor

Clarostat 240 C Variable Power Test Resistor 6 Decade Box 1Mohm Bench Top 225W
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US $699.99

LOT 100 RESISTOR VARIABLE 7688720 Mfr ROCK ISLAND ARSENAL 5905 00 204 6940
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US $555.00

SPECTROL MOD 308 USED VARIABLE RESISTOR W BERG RX18 2 SPEED REDUCER 308 RX182
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US $550.00

Clarostat 240 C Variable Power Test Resistor 6 Decade Box 1Mohm minus 1 999999
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US $729.00

TARGET INVENSYS SENSOR SYSTEMS VARIABLE RESISTOR PART 18 37904B01 200WS307
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US $450.00

complex variable resistor 71240000 01 new 8 contact
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US $360.00

Variable Resistor

Potentiometers & Their Classification

Potentiometers have found a range of uses in electronics sector. They are one of the most used physics lab equipments. They are actually variable resistors that are used for volume and gain controls and in several circuits. One can find numerous types of potentiometers in the market for different purposes. Potentiometers can be classified on a number of basis, one of them is whether they are adjustable or preset.

On the basis of input

Adjustable type potentiometers are used for functions where it requires a value to be set by the user. They have a spindle and can be used with a knob. Usually they found uses in radios for volume or tone controls.
The preset potentiometers are not available to the users as a piece of equipment. The value required for the circuit is usually feed within the production set-up and test stage during its manufacture. Preset potentiometers can be of two types, one is single turn adjustment and other is multi-turn adjustment.

On the basis of relationship between resistance & position along the track
On the basis of relationship between the resistance and the position along the track, potentiometer can be of following two types:

Linear potentiometer has a linear relationship between the resistance and the position around the track. For each degree around its travel the resistance varies with the same amount. All preset potentiometers are virtually linear type but same is not with adjustable ones.
Leaving behind the preset potentiometers, some of the non-preset potentiometers doesn't follow linear rule like logarithmic potentiometer. They follow logarithmic law in which the initial part of the travel saw a small change while it increases in latter part. In some cases anti-logarithmic laws are followed too.

On the basis of mechanical considerations
Potentiometer can also be classified on the basis of mechanical considerations. The ergonomics of a electronics device is largely affected by the way in which a potentiometer moves. The form of movement creates the electrical changes in the variable resistor and it is considered a major mechanical consideration. The two major types on these basis are:

The rotary variable resistors are the most common types. They use a rotary motion to move the slider around a track that compromises most of a circle, with contacts at either end of the track in the area where part of the circle is missing. Knobs are used on a spindle to control. Rotary potentiometers found uses in various applications ranging from volume controls on domestic radios to providing adjustments on test equipment.
Slider potentiometers slide in a straight line means in a linear fashion. Though they take up more front panel space but are easier to use under various circumstances. They are largely used for audio mixing and lighting desks. Sliders are easier to control precisely and it is easy to control even a number of sliders together.

About the Author

I am a laboratory analyst by profession working in this industry from last 10 years.I have been running a site www.laboratoryequipmentworld.com on laboratory equipments. It includes the largest range of laboratory apparatus and other updated info on market, trade fairs, news, etc.