A sensor is a component that converts a measured physical variable or a chemical effect into an analogue electrical output signal. The physical variable is an input signal that is not electrical, such as pressure, weight, temperature, radiation, magnetic flow, speed or another physical variable.
There are different types of sensor, such as:
Festo sensors are used in a wide range of industries and help to increase productivity and process reliability. They enable Festo to offer many industries, such as the automotive industry or food industry, everything from a single source.
Proximity sensors or cylinder sensors are used to generate an output signal indicating that a piston has reached its end position. In connection with pneumatic cylinders, these sensors are also often referred to as pneumatic cylinder sensor or limit switches. There are different types of sensors, two general types of proximity sensors:
• Electrical/electronic sensors
• Pneumatic sensors or pneumatic cylinder sensors.
Within this group we distinguish different types of sensors:
Contact-type (electrical) sensors
Contact-type (electronic) sensors.
The principle of the reed sensors consist of two contacts that can touch and also be separated.
The contacts are opened and closed by the action of a magnetic field. Under normal conditions, the contacts of a reed switch are closed or open, depending on the design. Once the action of a magnetic field becomes strong enough, the contacts open or close. The sensor measures the piston. This sensor is an inductive sensor that measures ferrous metal (metal objects). For example, an inductive sensor cannot detect the position of a plastic object. For this, you need a capacitive sensor that generates an electromagnetic field. Every time an object or liquids come into the range of the measurement, the electric field changes.
Sensor detects when a cylinder piston reaches an end position, special cylinders are used whose pistons are equipped with a magnet. Proximity sensors are installed in the end positions. Once the piston and magnet reach this end position, the field of the magnet activates the sensors, generating an immediate sensor feedback for further processing.
Depending on the design of the sensor in question, its contacts will open (normally closed type) or close (normally open type) when the sensor is attenuated. The type of magnet mounted on the cylinder piston and the strength of the field must be matched to the sensors used and the installation conditions. Excessive distance between the magnet and the sensors, or the presence of interfering materials in the magnetic field, or vibrations can prevent reliable signal generation.
Contact sensors are used when high load currents need to be switched. However, these types of sensors operate noticeably slowly due to their physical contact and are thus not suitable for use at high switching frequencies.
Inductive sensors work with a high-frequency magnetic field on the active surface of the sensors. When a metal object or permanent magnet enters this magnetic field, the sensor's current consumption changes. This change is then electronically evaluated and converted into a signal.
A non-contact sensor is particularly used in cases where the signal is routed directly to a programmable logic controller (PLC) for further processing. Moreover, this type of sensor achieves a significantly longer lifetime than reed-switch sensors. An important factor regarding reliability is that electronic sensor is free from contact collision. During operation of contact-type sensors, small sparks may jump between the contacts just before they touch. This has the same effect as activating the contacts several times in a row and leads to the generation of false reading, detecting objects that are not there. This phenomenon is known as contact bounce. So-called welding current-resistant sensors are a special type of non-contact sensor and operate on the same principle as these. Their special feature is that their switching state does not change once the sensor enters an alternating magnetic field of the kind present on welding production lines.
There are two reasons why this type of sensor is used on cylinders. The first reason is that with very small cylinders, it is difficult to find enough space to install a separate proximity sensor for each end position. Secondly, it is sometimes necessary to detect a total of three positions, namely two end positions and an intermediate position. In the case of a gripper, for example, these could be the positions "open", "closed" and "workpiece gripped". A Hall sensor is an ideal tool for this purpose.
The method of operation: As with other proximity sensors, a permanent magnet attached to the cylinder piston is used, while the Hall sensor is mounted at a fixed location on the cylinder housing. When a magnetic field penetrates the Hall sensor, it generates a voltage that is proportional to the strength of the magnetic field and therefore to the position of the magnet. The Hall sensor outputs an analogue voltage corresponding to the instantaneous strength of the magnetic field.
Electromechanical switches is a type of sensor that measures the movement of an object with physical contact. An object pushes against a switch and generates a circuit. Pressure and vacuum sensors measure compressed air pressure or compressed air vacuum. Flow sensors monitor the flow rate and are important in the industry to measure energy consumption or give an alarm. An optical sensor measures colors or object.
Optical sensors are used in industry, more precisely in factory automation, to detect objects and their characteristics using light as a medium. They are triggered, for example, when the light is interrupted or the intensity of the light has changed. They operate according to certain basic principles: diffuse sensors (with and without background suppression), retro-reflective sensors, infrared sensors, distance sensors and fork light barriers.
Analog sensors, touch sensors, digital sensors, measure temperature sensors, chemical sensors, humidity sensors, passive sensors, image sensor, light sensor, touch sensor, light intensity, current, radiation... is a technology that is not built at Festo.