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    A look at the industrial sensors landscape

    By Andrew Waugh, AutomationDirect A trip to the local coffee shop can serve to reveal the consequences of too much choice. Some patrons already understand

    A look at the industrial sensors landscape

    By Paul Heney | February 4, 2020

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    By Andrew Waugh, AutomationDirect

    A trip to the local coffee shop can serve to reveal the consequences of too much choice. Some patrons already understand the available possibilities from experience and quickly order exactly what they want. Others are confused or even intimidated by the variety of styles, flavors, sizes, and options — which may delay their selection — or even result in them buying something they didn’t quite want.

    Most people appreciate the benefit of having many choices available to them, but it is possible to have too many options. For these situations, having a summary, guidelines, or some other assistance aid selection.

    For designers of industrial automated equipment and systems, sensors are a crucial consideration because a control system operates most effectively with the proper feedback. Sensing the position of parts and product is fundamental in this regard, and there are many types of targets.

    Compounding the challenge are the wide variety of available sensing technologies and performance levels. Let’s examine some commonly available position sensing methods, benefits, and costs, sort of an introduction for those newer to the subject and a refresher for those with more experience.

    Sensor tradeoffs

    When it comes to industrial sensor selection, a basic balance must be achieved between cost and performance. The most straightforward cost is that of the sensor itself. More challenging to pin down are the initial design, installation, and configuration costs, along with required ongoing support and maintenance efforts.

    Performance can be measured in many ways. The most important point is for a sensor to reliably sense the appropriate target with sufficient accuracy. The form factor needs to physically fit the application, and the sensor must survive the environmental conditions.

    An inexpensive sensor that isn’t durable will require more frequent attention and replacement, significantly driving up costs over time. These costs are not just for servicing the problematic sensor, but also include downtime for the associated equipment.

    Note that for this discussion we are simply looking at discrete sensors for detecting the presence or absence of a target. However, versions of some technologies can return an analog signal to indicate how far away a target is, instead of just an on-off signal.

    Good engineering practice usually guides designers to follow a keep-it-simple approach, as long as the cost and performance needs are met. Therefore, the following sections are generally arranged to review sensing technologies in order of increasing cost and complexity.

    Limit switches

    The most basic sensing technology is the humble electromechanical limit switch. They are compact, easy to adjust, available with many actuator types, may be mounted in many ways, and can be quite accurate. Their biggest downfalls are related to their need to physically touch what they are sensing, and because they are mechanical with moving parts, they are more subject to wear and damage than other non-contact methods.

    When the geometry or motion of equipment or parts can be arranged so that a rugged limit switch will work, this is a reliable and inexpensive approach.

    Magnetic proximity switches

    Figure 1. Magnetic proximity switches can detect a magnetically equipped actuator position through the non-ferrous cylinder wall. All figures are courtesy of AutomationDirect.

    The most basic magnetic proximity switches were originally very sensitive mechanical reed limit switches that closed in the presence of magnets mounted on the target. The latest magnetic proximity switches are solid-state and much like inductive proximity switches (described in the next section) except they only detect magnets mounted on the targets, Figure 1.

    This may seem like a specialized and limited application, but because it works through non-ferrous materials like aluminum, the widest industrial use for these switches is to detect the position of a magnetically equipped actuating rod within a pneumatic cylinder. Alternately, a magnetic target can be installed on an object to deliver reliable sensing without false trips, which could occur in milling or cutting applications with errant metal particles.

    Because these sensors have a detection range of three to four times greater than inductive sensors, they allow for much better mounting flexibility. Also, the sensor can be mounted within an aluminum box for better protection while not impacting the detection ability.

    Inductive proximity sensors

    Figure 2. Inductive proximity switches are usually the best option for repeatably sensing metal objects when extreme accuracy is not needed.

    When the target to be sensed is metal, and if a small sensing range is acceptable, then an inductive proximity sensor will usually be the best option, Figure 2. Inductive proximity sensors are durable and extremely reliable solid-state technology. Their use of electromagnetic detection fields enables them to sense metal objects repeatably, but not with extreme accuracy. Note that they work best with ferrous materials, and for non-ferrous metals the sensing range is reduced.

    स्रोत : www.designworldonline.com

    5 Types of Proximity Sensors (Application and Advantages)

    You've probably heard about proximity sensors in smart phones and what they do, but here you'll also hear about other types of proximity sensors.

    5 Types of Proximity Sensors (Application and Advantages)

    By Ramzy / April 1, 2021

    Table of Contents

    A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. There are various types of proximity sensors out there in the market, but one can say this device often performs its object presence detection task by emitting an electromagnetic field or a beam of electromagnetic radiation ( infrared, for instance), and looking for changes in the field or return signal.

    If you are looking for proximity sensors, Linquip has the information you need, according to your application or requirement. We are here to help with any questions you may have about proximity sensors at Linquip. You can learn more about these sensors by visiting Linquip and reading the article “What Is Proximity Sensor?“.

    Find out More about Eectrical Device & Equipment in Linquip


    Are you in need of proximity sensor devices and equipment? At Linquip, you can see a wide range of Proximity Sensor Products for free. What proximity sensor equipment are you looking to buy? Linquip provides no-cost access to all available Proximity Sensor Devices for Sale. Linquip also offers you the option to send inquiries to all Proximity Sensor Suppliers and Companies and receive quotations for free if you are looking for proximity sensor equipment or device prices.

    The proximity sensors are available in different categories as per their detection. Some proximity sensors are useful to detect materials; whereas some are useful to detect different environmental conditions.

    According to its object detection method, there are four widely-used types of proximity sensors, as well as some newer high-end designs:

    Inductive Proximity SensorsCapacitive Proximity SensorsUltrasonic proximity SensorsIR Proximity SensorsHigh-end Proximity Sensors

    Before getting into any detail about different types of proximity sensors, let us quickly take a look at how they do what they do, and the benefits of using proximity sensors for environmental sensing applications.

    The Proximity Sensor and Its Benefits

    Proximity sensors are sensors that detect movement/presence of objects without physical contact and relay that information captured into an electrical signal. It can also be defined as a proximity switch, a definition given by the Japanese Industrial Standards (JIS) to all contactless detecting sensors.

    Find out More about Measurement, Testing and Control Device & Equipment in Linquip


    To further understand what proximity sensor is all about, we’ll take a look at its features. You will see the features of proximity sensors in the following compared to the traditional optical or contact sensors to have a better sense of why we use these devices.

    Contactless sensing

    Contactless proximity sensing allows for detection without touching the object, ensuring object stays well-conditioned

    Unaffected by surface conditions

    Proximity sensors are nearly unaffected by surface colors of objects since it mainly detects physical changes

    Suitability for wide range of applications

    Proximity sensors are suitable for damp conditions and wide temperature range usage, unlike your traditional optical detection.

    Proximity sensors are also applicable in phones as well, be it your Android or iOS devices. It consists of simple IR technology that switches on and off display accordingly to your usage. For example, it turns off your display when a phone call is ongoing such that you wouldn’t accidentally activate something while placing it near your cheeks!

    Longer service life

    Since a proximity sensor uses semiconductor outputs, there are no moving parts dependent on the operating cycle. Thus, its service life tends to be longer as compared to traditional sensors!

    High speed response rate

    Compared to switches where contact is required for sensing, proximity sensors offer a higher-speed response rate.

    Types of Proximity Sensors: Inductive Proximity Sensors

    Inductive proximity sensors are contactless sensors used to only detect metal objects. It’s based on the law of induction, driving a coil with an oscillator once a metallic object approaches it.

    It has two versions:

    Unshielded: Electromagnetic field generated by the coil is unrestricted, allowing for wider and greater sensing distances

    Shielded: Electromagnetic field generated is concentrated in the front, where sides of the sensor coil are covered up

    स्रोत : www.linquip.com

    Proximity Sensors Compared: Inductive, Capacitive, Photoelectric, and Ultrasonic

    Proximity sensors detect the presence or absence of objects using electromagnetic fields, light, and sound. There are many types, each suited to specific applications and environments.


    Proximity Sensors Compared: Inductive, Capacitive, Photoelectric, and Ultrasonic

    Sept. 1, 2001

    Proximity sensors detect the presence or absence of objects using electromagnetic fields, light, and sound. There are many types, each suited to specific applications and environments.

    Thomas A. Kinney • Application Engineer • Baumer Electric

    Download this article in .PDF format

    Proximity sensors detect the presence or absence of objects using electromagnetic fields, light, and sound. There are many types, each suited to specific applications and environments.

    Inductive sensors

    These non-contact proximity sensors detect ferrous targets, ideally mild steel thicker than one millimeter. They consist of four major components: a ferrite core with coils, an oscillator, a Schmitt trigger, and an output amplifier. The oscillator creates a symmetrical, oscillating magnetic field that radiates from the ferrite core and coil array at the sensing face. When a ferrous target enters this magnetic field, small independent electrical currents called eddy currents are induced on the metal’s surface. This changes the reluctance (natural frequency) of the magnetic circuit, which in turn reduces the oscillation amplitude. As more metal enters the sensing field the oscillation amplitude shrinks, and eventually collapses. (This is the “Eddy Current Killed Oscillator” or ECKO principle.) The Schmitt trigger responds to these amplitude changes, and adjusts sensor output. When the target finally moves from the sensor’s range, the circuit begins to oscillate again, and the Schmitt trigger returns the sensor to its previous output.

    If the sensor has a normally open configuration, its output is an on signal when the target enters the sensing zone. With normally closed, its output is an off signal with the target present. Output is then read by an external control unit (e.g. PLC, motion controller, smart drive) that converts the sensor on and off states into useable information. Inductive sensors are typically rated by frequency, or on/off cycles per second. Their speeds range from 10 to 20 Hz in ac, or 500 Hz to 5 kHz in dc. Because of magnetic field limitations, inductive sensors have a relatively narrow sensing range — from fractions of millimeters to 60 mm on average — though longer-range specialty products are available.

    To accommodate close ranges in the tight confines of industrial machinery, geometric and mounting styles available include shielded (flush), unshielded (non-flush), tubular, and rectangular “flat-pack”. Tubular sensors, by far the most popular, are available with diameters from 3 to 40 mm.

    But what inductive sensors lack in range, they make up in environment adaptability and metal-sensing versatility. With no moving parts to wear, proper setup guarantees long life. Special designs with IP ratings of 67 and higher are capable of withstanding the buildup of contaminants such as cutting fluids, grease, and non-metallic dust, both in the air and on the sensor itself. It should be noted that metallic contaminants (e.g. filings from cutting applications) sometimes affect the sensor’s performance. Inductive sensor housing is typically nickel-plated brass, stainless steel, or PBT plastic.

    Capacitive sensors

    Capacitive proximity sensors can detect both metallic and non-metallic targets in powder, granulate, liquid, and solid form. This, along with their ability to sense through nonferrous materials, makes them ideal for sight glass monitoring, tank liquid level detection, and hopper powder level recognition.

    In capacitive sensors, the two conduction plates (at different potentials) are housed in the sensing head and positioned to operate like an open capacitor. Air acts as an insulator; at rest there is little capacitance between the two plates. Like inductive sensors, these plates are linked to an oscillator, a Schmitt trigger, and an output amplifier. As a target enters the sensing zone the capacitance of the two plates increases, causing oscillator amplitude change, in turn changing the Schmitt trigger state, and creating an output signal. Note the difference between the inductive and capacitive sensors: inductive sensors oscillate until the target is present and capacitive sensors oscillate when the target is present.

    स्रोत : www.machinedesign.com

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