Linear Potentiometers

Worth knowing about displacement sensors with potentiometric technology

Guide for Linear Potentiometers

Linear Potentiometers

Potentiometric linear position sensors for distance measurement

The simplest conversion of a longitudinal movement into a proportional electrical quantity can still be performed with potentiometric measuring systems. These are absolute measuring systems with a resolution better than 0.01 mm and the well-known advantage that the signals are immediately displayed again in the correct position if the power supply fails. Our linear potentiometers cover mechanical measuring distances up to 2000 mm.

Whether as probe with spring return, with ball joints to compensate lateral misalignment, as slide-guided version or for installation in hydraulic applications, they all have a very high-quality resistive element made of conductive plastic (exceptions are the oil-filled with wirewound element). And despite the variety and diversity of the products, some demanding applications require sensor adaptation.

We at MEGATRON are your partner for this adaptation process and accompany you during the product selection, up to the end of the life cycle of your application. Particularly with potentiometric sensors, special adaptations of the measuring paths, the assemblies and improvements in component precision are often required, because in demanding special applications such as in medical technology, the standard variants often do not meet all requirements.


Guide for Linear Potentiometers
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What is a potentiometric linear sensor?

The measuring principle of the potentiometer was already described by Johann Christian Poggendorff in 1841 and has been used since the beginning of the use of electricity. A potentiometer has a resistance track on the surface of which a movable sliding contact is guided which taps a voltage potential. This resistance element can be circular or elongated.
However, the term "potentiometer" or "poti" for short is used today in technical practice mostly for angle sensors, i.e. for the round version.

Potentiometric displacement transducers, on the other hand, are sensors used for length measurement. These sensors are therefore more likely to be found under the name "linear potentiometers", or under the more general term "linear displacement transducers", when a resistance value is specified, or when it is obvious that potentiometric technology is involved.
For the operation of such a sensor a power supply is connected to the displacement transducer. A wiper is moved on the resistor track by means of mechanics (probe, slide, depending on the version), whose potential changes due to the displacement: The output voltage at the wiper is proportional to the position of the wiper on the resistor track. The resistor track is made of high-quality conductive plastic, which generates a continuously variable output signal and allows actuation speeds of up to 10 m/sec.


Advantages of linear potentiometers

  1. The measuring principle is an absolute procedure, i.e. the same measured value is immediately available again when switching on or after a power failure.
  2. It is a long proven technology and is easy to handle.
  3. Only a voltage source with low power is required, because the measured value is taken with low power.
  4. With potentiometric displacement sensors, displacements in the range from 0 to 10 mm, but also lengths of up to 2000 mm can be measured with a cost-effective sensor and further processed in analogue form.
  5. Linear potentiometers are very temperature stable in the voltage divider circuit
  6. Potentiometric displacement transducers are robust against EMC and ESD influences

The following must be observed with linear potentiometers

  • We recommend the overhead mounting, so that abrasion does not remain on the resistance element.
  • The displacement sensor should not be subjected to excessive vibration, as there is a risk that the slider will briefly lift off the track and the time curve of the measured value will be interrupted.
  • The sensors are not suitable for strongly oscillating applications. High frequency movements at one and the same point must be avoided at all costs! This leads to punctual abrasion, loss of signal quality of the resistor track, and the slider can also be permanently damaged.
  • Potentiometric displacement transducers with conductive plastic track may only be operated in voltage divider circuit, as the measured value must be taken with low power. In the rheostat circuit the resistor track with conductive plastic is permanently damaged. This means that linear potentiometers should not be used as variable resistors in a circuit.

Electrical connection and measurement example

Potentiometric displacement transducers always have three connections in the standard version, e.g. pins A, B and C. The displacement transducer is supplied with a DC voltage between points A and C. As an example, 10 V is assumed here. The connection A is at 0 V, the connection B thus at +10 V. The measurement of the displacement is based on the principle of the voltage divider circuit, i.e. the moving wiper (connection at pin B) has a certain potential relative to the reference point (A), depending on the position of the wiper between the start and end of the resistance track.

For the example shown (simplified):

  • If the displacement path is at the first end position, the wiper is at the beginning of the resistance track, so the voltage at pin B is approx. 0 V
  • The displacement is in the middle, the voltage at B is about 5 V
  • The displacement path is at the second end position, the wiper is at the end of the resistance track, the voltage at pin B is about +10 V

If the sensors are correctly connected in voltage divider circuitry, the voltage value at point B is independent of the absolute resistance value of the displacement transducer. However, please note here that this illustration is simplified, as different values for electrical and mechanical displacement travel still apply for the operation of the sensor (see mechanical and electrical travel). Furthermore, no sensor works without measurement inaccuracy. The deviation of the measurement result from the ideal straight line is specified by means of linearity specifications.


Load capacity of wiper and resistance element

Example Voltage U Resistance R Power P Application possible?
1 10 V 1 kΩ 0.1 Watt yes
2 20 V 1 kΩ 0.4 Watt no
3 25 V 5 kΩ 0.125 Watt yes
4 60 V 10 kΩ 0.36 Watt no
5 60 V 20 kΩ 0.18 Watt yes

Please take into account the maximum load capacity of the wiper and the resistance element when connecting. This information can be found in the respective data sheet. A too high current through the wiper leads to the immediate destruction of the wiper and/or the resistor track at the current position of the wiper.
The resistance value and the applied voltage are important for determining the power loss with which the displacement transducer is loaded. Here are some calculations using the example of the MM10 displacement transducer:

  • max. load capacity 0.2 Watt
  • available resistance values 1, 2, 5, 10, 20 or 50 kΩ

The following applies to the power loss:
P = U² / R (power P = voltage U² divided by resistance R)

On the basis of this calculation example it is immediately apparent that at an operating voltage of 20 V the displacement transducer with 1 kΩ cannot be used, because otherwise the power dissipation with which the resistance element is loaded becomes too great.
Please also note to use a very high input resistance when further processing the signal in an electronic system, so that the current via the slider (pin B) is as low as possible. To record the measured values, the voltage difference between pin B and pin A is measured.


Mechanical and electrical travel

The output characteristic curve of most potentiometric displacement sensors is not suitable for sensor operation over the entire available displacement range. A basic distinction must be made between the following displacement ranges:

  • Effective electrical limits: This is the actual travel to be used for the measurement. The linearity values specified in the data sheet apply to this travel and continuous operation should only take place within these limits.
  • Total electrical limits: Within this range the wiper provides an output signal, but this signal usually does not change at the ends of the travel, but remains constant. This is a kind of "dead zone", which is designed in this way for technical or design reasons and is not available with all sensors.
  • Mechanical limits: The actual displacement that the position sensor can perform. Mechanical stops prevent the slider from moving beyond the resistance path on most models.

For many models, the mechanical travel corresponds to the complete electrical travel. This leaves only two of the three ranges described above. Although this simplifies the consideration, the effective electrical travel must still be adjusted to the application when installing the sensor. Otherwise, the described dead range falsifies the measurement results. Please observe the notes on the data sheets of the model you have selected.


Oil-filled transducers

Potentiometric displacement sensors with oil filling are available for applications with special requirements on the durability of the sensor. They are the right choice especially for recording measured values at measuring points in filthy, moist or even corrosive environments (salts, corrosive gases). Applications for these sensors are found in heavy industry such as shipbuilding, mines, steelworks, chemical plants and many more.

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23 results found
Potentiometric Linear Transducer MM10
Potentiometric Linear Transducer MM10
Linear transducer in miniature design with rear and front guided push rod for 8 mm to 15 mm strokes
  • Linear potentiometer with almost infinite resolution
  • Space-saving mini design
  • Measuring lengths from 8 mm to 15 mm
  • Rear and front guided push rod
  • Long lifetime
Potentiometric Linear Transducer RC13
Potentiometric Linear Transducer RC13
Displacement sensor in robust and compact design with protection class IP60 and front guided push rod in three mounting variants for 25 to 250 mm strokes
  • Compact displacement sensor
  • For harsh environmental conditions - protection class IP60
  • Mounting by ball joints, mounting brackets or flange
  • Long lifetime and accuracy
  • Measuring lengths from 25 mm to 300 mm
Potentiometric Linear Transducer CLP13
Potentiometric Linear Transducer CLP13
Displacement sensor in space-saving design and front guided push rod for 13 to 100 mm strokes
  • Linear potentiometer with almost infinite resolution
  • Space-saving compact design
  • Measuring lengths from 13 mm to 100 mm
  • Also available with spring return probe
  • Long lifetime
Potentiometric Linear Transducer RC20
Potentiometric Linear Transducer RC20
Displacement sensor in robust design IP60/IP67 and front guided push rod in three mounting variants in measuring lengths 10 to 300 mm
  • For harsh environmental conditions - protection class up to IP67
  • Mounting by ball joints, mounting brackets or flange
  • Long life span and high accuracy
  • Measuring lengths from 10 mm to 300 mm
Potentiometric Linear Transducer MM
Potentiometric Linear Transducer MM
Very compact linear transducer with rear and front guided push rod and pilot ring for 10 to 30 mm strokes
  • Space-saving due to small dimensions
  • Long lifespan and high accuracy
  • Measuring lengths from 10 mm to 30 mm
  • Rear and front guided push rod
  • Two M3 threads and 10 mm flange diameter for easy integration
Potentiometric Linear Transducer CLP21
Potentiometric Linear Transducer CLP21
Compact and robust displacement sensor with front guided push rod in measuring lengths 15..100 mm
  • Compact and robust design
  • With front guided push rod
  • Available as a probe
  • Measuring lengths from 25 mm to 100 mm
  • Long lifetime and high accuracy
Potentiometric Linear Transducer SPR18
Potentiometric Linear Transducer SPR18
Displacement sensor in compact industrial design with spring-suspended probe tip for 25 to 100 mm strokes
  • Compact industrial design
  • With spring-suspended probe tip
  • Long lifetime and high accuracy
  • Linear potentiometer with almost infinite resolution
  • Measuring lengths from 25 mm to 100 mm
Potentiometric Linear Transducer SPI18
Potentiometric Linear Transducer SPI18
Displacement sensor in compact industrial design with front guided push rod and ball joint for 25 to 200 mm strokes
  • In a compact industrial design
  • Front guided push rod and ball joints
  • Long lifespan and accuracy
  • Linear potentiometer with almost infinite resolution
  • Measuring lengths from 25 mm to 200 mm
Potentiometric Linear Transducer RC35
Potentiometric Linear Transducer RC35
Displacement sensor in very robust design with protection class up to IP67, ball joints and front guided push rod for 50 to 750 mm
  • For harsh environmental conditions up to IP67
  • Coupling with ball joints
  • Very long lifetime and very high accuracy
  • Measuring lengths from 50 mm to 750 mm
Potentiometric Linear Transducer REM13
Potentiometric Linear Transducer REM13
Compact displacement sensor in space-saving design for 20 bar operating pressure in protection class IP67 for 50 mm to 1000 mm
  • Space-saving and compact construction
  • With external magnetic cursor
  • High degree of protection IP67 and operating pressure up to 20 bar
  • Measuring lengths from 50 to 1000 mm
  • With cable or plug
  • Cursor with or without ball joint
Potentiometric Linear Transducer MBX
Potentiometric linear transducer MBX
Extremely flat linear transducer with only 7 mm height and universal cursor ideal for tight space for 50 to 200 mm strokes
  • Minimum height only < 7 mm
  • Easy mounting
  • Flexible mechanical coupling due to universal cursor
  • No push rod necessary
Linear sensor MBH
Potentiometric linear transducer MBH
Potentiometric linear transducer in open and flat design with a space saving slider construction for 100 mm strokes. Waterproof sensor-foil element
  • Hermetically encapsulated sensor element
  • Sealed round cable outlet
  • Saves space by flat construction and by slider coupling
  • Integrated end stops
  • 3 million sliding movements
Potentiometric Linear Transducer CFL
Potentiometric linear position sensor CFL
Very precise displacement sensors in open design with long lifespan in measuring lengths 100..1000 mm
Potentiometric Linear Transducer CD18
Potentiometric linear position sensor CD18
Potentiometric position transducer CD18 with rear and front guided push rod and pilot ring in measuring lengths of 25..150 mm
Potentiometric Linear Transducer CH37
Potentiometric linear position sensor CH37
Linear position sensor CH37 for use in hydraulic cylinders with up to 340 bar for 100 to 550 mm strokes
  • Internal or external flange design
  • Space saving design
  • Independent linearity ±0.1 %
  • Conductive plastic with almost infinite resolution
  • Measuring lengths from 50 mm to 550 mm
  • Long life span (100 million movements)
Potentiometric Linear Transducer CR18
Potentiometric Linear Transducer CR18
Displacement sensor in compact industrial design with spring-suspended probe tip or tip with roller bearing for 10 to 100 mm strokes
  • Compact industrial design
  • With spring-suspended probe tip or tip with roller bearing
  • Long lifespan and high accuracy
  • Linear potentiometer with almost infinite resolution
  • Measuring lengths from 10 mm to 100 mm
Potentiometric Linear Transducer HEM12
Potentiometric Linear Transducer HEM12
Displacement sensor for hydraulic applications up to 250 bar and IP67 protection for 50 to 1000 mm strokes
  • High degree of protection IP67 and max. 250 bar operating pressure
  • With external magnetic cursor - capsule of the sensor element
  • Mounting via internal or external flange
  • Measuring lengths from 50 mm to 1000 mm
  • Long lifetime (up to 100 million movements)
Potentiometric Linear Transducer HEM12
Potentiometric Linear Sensor HEM12E with Electronics
Displacement sensor with integrated signal-converter for hydraulic applications up to 250 bar and IP67 protection for 50 to 1000 mm strokes
  • With integrated signal-converter
  • High degree of protection IP67 and max. 250 bar operating pressure
  • With external magnetic drag - capsule of the sensor element
  • Mounting via internal or external flange
  • Measuring lengths from 50 mm to 1000 mm
  • Long lifetime (up to 100 million movements)
Potentiometric Linear Transducer HEM16
Potentiometric Linear Transducer HEM16
Very accurate displacement sensor for hydraulic applications up to 250 bar with protection IP67 for 50 to 1000 mm strokes
  • High accuracy due to very good linearity
  • For hydraulic applications up to 250 bar (peak 400 bar)
  • With external cursor - encapsulation of the sensor element
  • Mounting via internal or external flange
  • Measuring strokes from 50 mm to 1000 mm
  • Long lifespan (up to 100 million axis movements)
Potentiometric Linear Transducer MMS33
Potentiometric Linear Transducer MMS33
Front guided push rod displacement sensor in rugged design up to IP67 and length from 50 to 900 mm for applications with strong vibrations
  • Robust design in protection class up to IP67
  • Measuring lengths from 50 to 900 mm
  • With front guided push rod
  • Simple coupling with ball joints (not included)
  • For applications with strong vibrations
Potentiometric Linear Transducer MSL38
Potentiometric Linear Transducer MSL38
Displacement sensor for measuring distances from 100 mm to 2000 mm with space-saving cursor for industrial environments
  • Space saving cursor construction
  • Easy coupling by link ball on cursor
  • Measuring lengths from 100 mm to 2000 mm
  • Long lifetime (up to 100 million movements)
Potentiometric oilfilled Linear Transducer WGO20
Potentiometric oil filled linear position sensor WGO20
Potentiometric linear position sensor with oil filling in measuring length 50..200 mm for use in difficult environmental conditions
Potentiometric oilfilled Linear Transducer WGO40
Potentiometric oil filled linear position sensor WGO40
Potentiometric linear position sensor with oil filling in measuring length 100..500 mm for use in difficult environmental conditions
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