Food for Thought: Should a Fork Sensor be Your First Choice?

When it comes to reliability and accuracy, there is no optical sensing mode better than the through-beam photoelectric sensor. Its reliability is a result of the extraordinary levels of excess gain – the measurement of light energy above the level required for normal sensing. The more excess gain, the more tolerant of dirt, moisture and debris accumulating on the sensor.

Excess gain comparison

The accuracy of through-beams results from a tight, well-defined sensing area. This chart shows a comparison between the popular sensing modes.

When it comes to reliability and accuracy, there is no optical sensing mode better than the through-beam photoelectric sensor. Its reliability is a result of the extraordinary levels of excess gain – the measurement of light energy above the level required for normal sensing. The more excess gain, the more tolerant of dirt, moisture and debris accumulating on the sensor. The accuracy of through-beams results from a tight, well-defined sensing area. This chart shows a comparison between the popular sensing modes.

The sensing area starts with an emitted beam projected onto the receiver. The wider the emitted beam, the easier to align. Once aligned, you now have the effective beam which is basically the size of the emitter and receiver lens. The smaller the lens, the smaller the effective beam. Apertures can also be used to narrow down the effective beam.

Simple detection

A target is detected when it breaks the effective beam. The simple detection principle means these sensors can detect anything, regardless of color, texture, or reflectivity. They are generally used in applications that require a sensing range of 2mm to 100m! The simplicity of their operation and wide range make them a go-to detection solution across industries.

Fork sensor, effective beam_emitted beamTraditional through-beam sensors consist of two separate pieces which must be separately mounted and wired, and perfectly aligned to work. This can be inconvenient and time consuming. But for those applications that can use an opening from 5mm to 220mm, self-contained through-beam sensors, also called fork sensors, provide the usefulness of traditional through-beams without the trouble of alignment. With the emitter and receiver in one housing, they are automatically aligned and require only half the wiring effort.

Light types

Available in four different light types – red light, pinpoint red light, infrared and laser – they can detect even difficult and tiny parts. Red light and pinpoint red light are used for most applications, while laser light is used for small part detection, as small as 0.08 mm. Infrared improves detection efforts in dirty environments.

Through-beam sensors are a go-to solution for photoelectric applications, but with tough housings, various lighting options, and the ease of installation and alignment, fork sensors should be first on your list of photoelectric sensors to consider.

Fork Sensors, the Best Choice for Range, Reliability, Ease of Installation

Photoelectric sensors are a staple within many industries when it comes to automation thanks to their non-contact detection over longer ranges than many other sensing types. Also available in a variety of housing types and protection classes to meet the specific demands of an application, they offer manufacturers many different variants and models. The range of styles can make selecting the perfect photoelectric sensor for your specific application challenging. This post highlights the benefits of through-beam sensors and why fork sensors specifically, are often the ideal sensor for the job.

Through-beam sensors can detect anything, regardless of color, texture or reflectivity. This makes them highly efficient in any application where material or parts need to be detected during the process. They require an emitter and receiver. The emitter sends a light beam toward the receiver. When this light beam is blocked, the sensor will trigger. A common example of this is the sensor system on a garage door that detects obstructions and keeps the door from closing. (The software can also inverse this, so the sensor triggers when the light beam is not obstructed. Read more about these light-on/dark-on modes).

Traditional Through-Beams vs. Fork Sensors

Through-beam photoelectric sensors are simple technology that are non-contact, reliable and can operate over distances up to 100 meters, making them a go-to for many applications. But they aren’t without fault. Because the emitter and receiver are typically in separate housings, the two parts must line up perfectly to work. This alignment takes extra time during assembly and is prone to problems in the future if the emitter or receiver move,  even slightly. Machine vibrations can cause a misalignment.

Fork sensors, also called C slot or U slot sensors, incorporate both the emitter and the receiver into a single body, providing the benefits of a through-beam sensor without the installation issues.

This allows for reduced installation and maintenance time of the sensor in several ways:

    • Mounting a single sensor instead of two
    • Half as many cables needed for networking
    • No touchy alignment needed when installing the sensor
    • No maintenance needed re-aligning the sensors in the future

Photoelectric fork sensors come with sensing windows widths up to 220 mm and a range of light sources to accommodate many application needs. Check them out the next time you are considering a photoelectric sensor and see if they’re the best choice for your application.

Smart IO-Link Sensors for Smart Factories

Digitizing the production world in the age of Industry 4.0 increases the need for information between the various levels of the automation pyramid from the sensor/actuator level up to the enterprise management level. Sensors are the eyes and ears of automation technology, without which there would be no data for such a cross-level flow of information. They are at the scene of the action in the system and provide valuable information as the basis for implementing modern production processes. This in turn allows smart maintenance or repair concepts to be realized, preventing production scrap and increasing system uptime.

This digitizing begins with the sensor itself. Digitizing requires intelligent sensors to enrich equipment models with real data and to gain clarity over equipment and production status. For this, the “eyes and ears” of automation provide additional information beyond their primary function. In addition to data for service life, load level and damage detection environmental information such as temperature, contamination or quality of the alignment with the target object is required.

One Sensor – Multiple Functions

This photoelectric sensor offers these benefits. Along with the switching signal, it also uses IO-Link to provide valuable information about the sensor status or the current ambient conditions. This versatile sensor uses red light and lets you choose from among four sensor modes: background suppression, energetic diffuse, retroreflective or through-beam sensor. These four sensing principles are the most common in use all over the world in photoelectric sensors and have proven themselves in countless industrial applications. In production this gives you additional flexibility, since the sensor principles can be changed at any time, even on-the-fly. Very different objects can always be reliably detected in changing operating conditions. Inventory is also simplified. Instead of four different devices, only one needs to be stocked. Sensor replacement is easy and uncomplicated, since the parameter sets can be updated and loaded via IO-Link at any time. Intelligent sensors are ideal for use with IO-Link and uses data retention to eliminate cumbersome manual setting. All the sensor functions can be configured over IO-Link, so that a remote teach-in can be initiated by the controller.

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Diagnostics – Smart and Effective

New diagnostics functions also represent a key feature of an intelligent sensor. The additional sensor data generated here lets you realize intelligent maintenance concepts to significantly improve system uptime. An operating hours counter is often built in as an important aid for predictive maintenance.

The light emission values are extremely helpful in many applications, for example, when the ambient conditions result in increased sensor contamination. These values are made available over IO-Link as raw data to be used for trend analyses. A good example of this is the production of automobile tires. If the transport line of freshly vulcanized tires suddenly stops due to a dirty sensor, the tires will bump into each other, resulting in expensive scrap as the still-soft tires are deformed. This also results in a production downtime until the transport line has been cleared, and in the worst case the promised delivery quantities will not be met. Smart sensors, which provide corresponding diagnostic possibilities, quickly pay for themselves in such cases. The light remission values let the plant operator know the degree of sensor contamination so he can initiate a cleaning measure before it comes to a costly production stop.

In the same way, the light remission value BOS21M_ADCAP_Produktbild.png allows you to continuously monitor the quality of the sensor signal. Sooner or later equipment will be subject to vibration or other external influences which result in gradual mechanical misalignment. Over time, the signal quality is degraded as a result and with it the reliability and precision of the object detection. Until now there was no way to recognize this creeping degradation or to evaluate it. Sensors with a preset threshold do let you know when the received amount of light is insufficient, but they are not able to derive a trend from the raw data and perform a quantitative and qualitative evaluation of the detection certainty.

When it comes to operating security, intelligent sensors offer even more. Photoelectric sensors have the possibility to directly monitor the output of the emitter LED. This allows critical operating conditions caused by aging of the LED to be recognized and responded to early. In a similar way, the sensors interior temperature and the supply voltage are monitored as well. Both parameters give you solid information about the load condition of the sensor and with it the failure risk.

Flexible and Clever

Increasing automation is resulting in more and more sensors and devices in plant systems. Along with this, the quantity of transported data that has to be managed by fieldbus nodes and controllers is rising as well. Here intelligent sensors offer great potential for relieving the host controller while at the same time reducing data traffic on the fieldbus. Pre-processing the detection signals right in the sensor represents a noticeable improvement.  A freely configurable count function offers several counting and reset options for a wide variety of applications. The count pulses are evaluated directly in the sensor – without having to pass the pulses themselves on to the controller. Instead, the sensor provides status signals, e.g. when one of the previously configured limit values has been reached. This all happens directly in the sensor, and ensures fast-running processes regardless of the IO-Link data transmission speed.

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Industry 4.0 Benefits

In the age of Industry 4.0 and IoT, the significance of intelligent sensors is increasing. There is a high demand from end users for these sensors since these functions enable them to use their equipment and machines with far greater flexibility than ever before. At the same time they are also the ones who have the greatest advantage when it comes to preventing downtimes and production scrap. Intelligent sensors make it possible to implement intelligent production systems, and the data which they provide enables intelligent control of these systems. In interaction with all intelligent components this enables more efficient utilization of all the machines in a plant and ensures better use of the existing resources. With the increasing spread of Industry 4.0 and IoT solutions, the demand for intelligent sensors as data providers will also continue to grow. In the future, intelligent sensors will be a permanent and necessary component of modern and self-regulating systems, and will therefore have a firm place in every sensor portfolio.

To learn more about these smart sensors, visit www.balluff.com.

The Perfect Photoelectric Sensor – Imagine No More

In my last blog, Imagine the Perfect Photoelectric Sensor, I discussed the possibilities of a single part number that could be configured for any of the basic sensing modes: through-beam, retroreflective, background suppression and diffuse. This perfect sensor would also have the ability to change the sensing mode on the fly and download the required parameters for a changing process or format change.  Additionally, it would have the ability to teach the sensing switch points on the fly, change the hysteresis, and have variable counter and time delays.

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Tomorrow is here today! There is no need to imagine any longer, technology has taken another giant leap forward in the photoelectric world.  Imagine the possibilities!

Below are just some of the features of this leading edge technology sensor. OEM’s now have the opportunity to have one sensor solve multiple applications.  End users can now reduce their spare inventory.

To learn more visit www.balluff.com.

 

Fork Sensors – The Ideal Through-Beam

Through-beam sensors are a true time proven solution to many photoelectric applications.  These sensors can detect anything regardless of color, texture or reflectivity, all that needs to happen is the light beam needs to be blocked.  Add an optional aperture and you can detect even the smallest of parts.  With the various light sources available and you can detect small parts (with a laser light) or blast through the harshest of environments with an infrared light source.  These sensors come in several housings or styles for instance tubular (as small as 8mm), block, fiber optic and the fork style sensor.

Through-beam sensors are used in applications that require sensing ranges from 2 millimeters to 100 meters and in some cases longer.  Since these sensors require a light emitter and a receiver that are in separate housings, you have to mount and wire each component separately.  Once mounted you have the task of aligning the receiver to the emitter, which could be a tedious task.  Just imagine trying to line up the devices that use an infrared light source with a working range of 50 meters or even 150 millimeters.

forksensorFork sensors, also referred to, as c slot or u slot, are the ideal through-beam sensor.  First, they are self-contained in one housing so there is no need to align the emitter and receiver.  This is important because in the harsh environments if the sensor is bumped or jarred the receiver and emitter stays aligned.  Secondly, the housings are typically metal offering an extremely robust sensor.  Third, since the sensor is integrated into one housing installation is much easier, one part to mount and only one wiring connection.  These sensors are available from 5mm to 220 mm wide openings.

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Timing is everything – Which light is the right light?

Shortly after posting my last blog, Which light is the right light, I had a customer call with a problem in a machining cell.  They are using a self-contained through-beam sensor, in the form of a fork sensor, with a red light source. They required a small light spot to detect a tool.  As in most machining centers, there is a lot of coolant flying around in the cell and a fine mist in the air.  When water based coolants dry, they separate and leave a white film on surfaces, including photoelectric lenses.  This customer had to shut down their cell and clean off the lens at least once per shift, which was costing them production, time, and money because of false signals.

As we spoke on the phone, I suggested that they use the infrared version because we can burn through the contamination in the environment, in this case the film left behind from the coolant.  The customer wanted some sort of idea of how much residue we could burn through so I did some simple testing and sent him the following pictures.  Picture 1 is a heavy dusting, of all things, coffee creamer.  Picture 2 is a nice dollop of grease from a grease gun and picture 3 is a film of hand cream.

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