A photoelectric sensor is formed by an element that emits light radiations which, directly or indirectly, reach the receiver .The level of the light signal is converted into an electrical signal amplified and elaborated to drive the output state of the sensor. A variation of the received light radiations indicates the presence or the absence of the target, or its variation in terms of: color, position, reflection. The light radiation can be visible emission or outside the visible band and it is usually modulated (emission and reception under impulsive).
Sensors, Safety e Encoders
Starting from 1971 M.D. Micro Detectors S.p.A. is designing and manufacturing a wide range of industrial sensors.
As many other successful business stories typical of the region, M.D. Micro Detectors was born in a garage following the inspiration of a Physics teacher of a Techincal Institute in Modena and constantly developed over the years, up to the present days.
Technology, Quality and Reliability of products, as well as the Customer Orientation, have always been the main drivers of the Company Strategy.
To better understand the technological level just think that MD, for example, was the first industry to produce photoelectric sensors in the M18 cylindrical shape, become an international standard, as well as to realize different types of Area Sensors.
M.D. Micro Detectors? quality is confirmed by many certifications that the Company got during the years: the System is ISO 9001:2008 and many products are CE, ATEX, cULus, Diversey, TÜV and ECOLAB certified.
Wide range of sensors (photoelectric, inductive, capacitive, ultrasonic and area), safety light curtains and encoders.
The electric current, which flows inside the coil, generates an oscillating electromagnetic field. When a metallic item (object) gets into the field, the induced eddy currents decrease the amplitude of the oscillation. When this oscillation becomes lower than a specific threshold, the sensor switches. The parting of the metallic item reestablishes energy to the electromagnetic field; consequently the amplitude of the field increases until , above a certain threshold, the sensor switches again, returning to the initial state. Only metal items can generate enough eddy currents to modify the magnetic field?s oscillation amplitude generated by the sensor. Therefore, an inductive sensor detects only metallic items without being influenced by the presence of other materials, both solid (wood, glass, plastic, etc.) and liquids (water, oils, etc).
The capacitive probe generates an electrostatic field. When an item gets close to the capacitive probe, the oscillator starts to oscillate (and the amplitude). The amplitude of oscillations increases as the target moves closer to the sensor. Above a certain amplitude, the detection circuit switches the sensor. When the item separates from the probe the amplitude of the oscillations decreases until the sensor reaches a specific, at which the sensor switches again to the initial conditions.
Ultrasonic sensors are composed by: ultrasonic transducer, oscillator, trigger circuit and output circuit. There are three working principles: direct diffusion; retroreflection; emitter and receiver. Ultrasonic sensor can detect any kind of targets (more or less). The effective detection distance depends on: target dimensions (more the target is big, more ultra-sonic signal is reflected, higher the sensing distance that it is possible to reach), materials (compact targets, as metal, wood, liquids, reflect a lot of the ultrasonic signal ? low density materials, as powders, foams, absorb the majority of the ultrasonic beam). Sound absorbing materials can be detected only at very low distance.
Type-T Optoelectronic scanners are made up of two elements; an emitter and a receiver. The emitter has an optical unit that consists of an array of photoemitters which emit a series of narrow luminous pulses to the receiver in a consecutive well-defined manner. Luminous radiation is generated by a solid- state source made up of high-performance long-lasting semiconductor elements. This radiation can be from outside the visible band. The receiver has an optical unit which is made up of an array of photoreceivers which correspond geometrically to those of the emitter. The luminous radiation reaching the photoreceivers is converted to an electric signal, amplified and processed in order to drive receiver output elements. As there is synchronous reading of the luminous pulse, a synchronous signal must be transmitted between emitter/receiver. Detection occurs when the path of the beam is interrupted by the presence of an opaque object.
Light Curtains are electro sensitive devices using one or more light beams, emitted by an Emitter and received by a Receiver, to create an intangible controlled area.
When the chosen safety device is a photo-electric barrier (AOPD Active Optoelectronic Protective Device), it shall necessary belong to TYPE 2 or TYPE 4 as established by the International Standard IEC 61496 1-2.
Some advantages: Effective protection in the event of fatigue or distraction of the operator; Increase in the productive capacity of the machine as the light curtain does not require the manual handling of physical guards or waiting for them to open; Faster machine loading/unloading operations; Reduced times of approach to the working areas.
An encoder is a rotary transducer that converts an angular movement into a series of electrical digital pulses. If associated to racks or endless screws, these generated pulses can be used to control angular or linear movements. During rotation, electrical signals can be elaborated by numerical controls (CNC), programmable logic controls (PLC), control systems, etc. Main applications of these transducers are: machinery, robots, motor feedback, measure and control devices. In M.D. Micro Detectors encoders the angular movement transduction is based on the photoelectric scanning principle.
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