So what's so great about a Variohm position sensor, anyway?
When we refer nowadays to a potentiometer as a sensor, it is important to bear in mind the statements made here only apply if the potentiometer is connected as a voltage divider rather than as a variable resistor.
The main purpose of the article is to discuss the advantages of Conductive Plastic Potentiometers.
Rapid developments in the fields of control engineering, microprocessor and semiconductor technology have resulted in the widespread use of electronically controlled systems in every branch of industry today. This has created a need for sensors that are inexpensive, whilst at the same time being sufficiently robust, both electrically and mechanically to withstand a wide range of temperatures (e.g. from -40 to +160 degrees centigrade) and offer long service life coupled with high accuracy & repeatability hence the development in conductive plastic potentiometers.
We have given a brief explanation of the Potentiometer and, in particular, the advantages of conductive plastic potentiometers and their uses below. At the bottom of the article you will find a useful link regarding Potentiometers and technical definition.
The Potentiometer Principle
In simple terms a Potentiometer proportionally divides an applied voltage over it’s operational range, (otherwise known as it’s electrical output), which can be either a Linear or Rotary movement. The use of a Potentiometer requires either a regulated voltage or current supply source, often referred to as a signal conditioner, to ensure that the Sensor output remains stable and constant. If the supply is unstable the output will reflect this.
The Advantages of Conductive Plastic Potentiometers
There are several variants of Potentiometer technology but predominately Conductive Plastic is the most widely used and supplied by Variohm.
The advantages of conductive plastic potentiometers are;
· Longevity of operational life
· Temperature stability
· Virtually infinite resolution
· Improved linearity
· Laser trimming of the track
The use of multi fingered precious metal elastomer dampened wipers, (cats claw configuration) ensures best wiper contact even in the most severe applications to include high vibration or operating speeds (typically up to 10 m/s). These use both a conductive and collector track whereby the wiper ‘bridges’ the two tracks proving the proportional output relevant to the position, which can be shown as a simple circuit.
Even in the greater use of non-contacting measurement technologies, Conductive Plastic Potentiometers offer many advantages in being a simple 3 wire device.
· They are typically less expensive
· Offer the absence of electronics (less components to fail)
· Have the ability for use within greater temperature ranges
Although the sensor is subject to wear over time, it is clear when the end of life has been reached, it will result in a degradation in the quality of the output signal. The sensor can then be serviced or replaced accordingly, rather than failing without warning, another advantage of using potentiometers.