Conductive Plastic Potentiometers

These potentiometers have several advantages and special features compared to other resistance elements

Guide for Conductive Plastic Potentiometers

Conductive Plastic Potentiometers

Conductive plastic potentiometers offer an almost infinite resolution for angles up to max. 355° at max. 400 rpm thanks to the very smooth resistance track. In addition, they achieve top levels of lifetime and quality and provide an absolute, analogue output signal without steps.

In terms of design, the portfolio ranges from miniaturized, extremely compact conductive plastic potentiometers with a minimum installation depth of < 8 mm to completely sealed housings with protection class IP65. And yet there are applications that require additional technical product adaptation.

MEGATRON is your specialist for these matters. Within the scope of our consultation we define with you the optimal product for your "design in". With high delivery reliability and assured quality products, we focus on long-term partnerships and accompany you throughout the entire service life of your application.

Basic questions about potentiometers? Here you will find the answers

Resistance element and resolution

Conductive plastic potentiometers have a conductive plastic resistance element, from which the name for these potentiometers is derived. There is a conductive plastic layer on a carrier material. These layers are extremely smooth, mirror-like resistance tracks. In the application, these potentiometers provide a continuous signal without steps, have a quasi-infinite resolution and enable a very long lifespan of ≥50 million revolutions. Furthermore, conductive plastic potentiometers achieve excellent independent linearities of up to 0.02%. Conductive plastic potentiometers, which are manufactured in a "co-molded" production process, have an additional advantage: the adjacent connection transitions to the resistor track are manufactured very precisely, so that the wiper is much less worn when passing over the ends of the resistor track.

Conductive Plastic Element

Circuit type

Conductive plastic potentiometers must never be used as variable resistors (rheostats), but only in voltage divider circuits. Otherwise, the resistor element will be damaged. Potentiometers generally show their strengths in voltage divider circuits. Temperature has hardly any influence on the output signal, because the tapped voltage at the slider or the electrical potential at the output remains largely unaffected here, since the divider ratio does not change.

Load capacity of the resistance element

Example	Voltage U	Resistance R	Power P	Application possible?
1	20 V	1 kΩ	0.4 Watt	yes
2	30 V	1 kΩ	0.9 Watt	yes
3	50 V	1 kΩ	2.5 Watt	no
4	100 V	5 kΩ	2 Watt	no
5	100 V	10 kΩ	1 Watt	yes

Example MPA20/21 series

available resistance values (0.5..100 kΩ) 1, 2, 5, 10, 50 kΩ
max. load capacity 1 Watt

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

On the basis of this calculation example it is immediately apparent that at an operating voltage of 50 V the potentiometer with 1 kΩ cannot be used. Because otherwise the power with which the resistance element is loaded is too high. Please also take into account the additional restrictions for the ambient temperature.

Please note that very high-resistance conductive plastic versions have a less favorable slider contact resistance, as the latter also increases if the conductive plastic layer itself has a higher resistance.

Resistance elements in comparison

Resistive element	Conductive Plastic	Wirewound	Hybrid
Lifespan	++	0	+
Signal quality / resolution	+++	+	+++
Linearity	+++	++	++
Electrical travel	max. 360°	10800°	max. 3600°
Operational speed	++	-	++
Max. wiper current	-	+	-
Shock / Vibration	-	--	--

Legend: +++ best | ++ very good | + good | 0 OK | - low | -- unfavourable | --- not appropriate

Decision support

The choice of the right potentiometer technology depends on various factors. If your application places high demands on lifespan and tight linearity tolerances, conductive plastic technology is a good choice for singleturn applications. Conductive plastic offers the highest lifespan with up to 50 million shaft revolutions and best values in linearity with up to 0.02% tolerance in very compact designs (e.g. MCP22). Thanks to the very smooth resistive track and very low signal noise, almost infinite resolution is achieved. In addition, the design allows adjustment speeds of up to 400 rpm.

Please note, however, that conductive plastic potentiometers are not available as helical multiturn potentiometers. Conductive plastic potentiometers must be connected in voltage divider circuit and the wiper current must be limited to a minimum.

Comparison between conductive plastic and wirewound potentiometers

If you compare conductive plastic with wirewound potentiometers, it is important to mention that the tolerance of the total resistance of conductive plastic potentiometers is generally somewhat larger than that of wirewound potentiometers. Since the application must always be in the voltage divider circuit, this tolerance is not relevant for the useful signal. However, if the power dissipation of an electrical circuit must be known exactly, these tolerance should be taken into account.

On the other hand, wirewound potentiometers "tolerate" slightly higher current values than conductive plastic potentiometers, have excellent resistance tolerance values and very good linearity values. However, the surface of the resistive element is somewhat rougher due to its design and generates noticeable small steps in the output signal. The wiper is also subjected to greater stress due to the resistor design, which has an effect on the lifespan and in many cases is significantly below that of conductive plastic potentiometers.

Hybrid potentiometers are for multiturn tasks

If similar values of conductive plastic potentiometers are required for multiturn tasks ≥360°, they are found in our hybrid potentiometers. In wich a wirewound resistor track is coated with conductive plastic. This protects the wiper and also enables a smooth output signal, almost infinite resolution and higher adjustment speeds.

Conductive plastic potentiometers in tandem designs
Conductive plastic potentiometers can also be equipped like wirewound or hybrid potentiometers in tandem design. What you have to consider, you can find here.

Product customizations

Scroll

MP20/21

Economical and compact precision potentiometer in Ø22 mm housing with long lifespan and many options