Sensor Technology Easily Network Laser Sensors Via IO-Link

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Micro-Epsilon Messtechnik GmbH & Co. KG

FAULHABER Drive Systems

Wuxi InfiMotion Technology Co., Ltd.

To network laser triangulation sensors, Micro-Epsilon equips its products with the IO-Link interface. Their advantages are demonstrated, for example, when measuring board contours in a sawmill.

With the help of laser triangulation sensors, parameters such as displacement, distance, and position can be measured non-contact and wear-free. The most important features of the sensors are high performance, a compact design, and the ability to stabilize the signal on changing surfaces.

The laser triangulation sensors in Micro-Epsilon's portfolio combine a compact design with an integrated controller and operation via a web interface. High-precision measurement is achieved through the smallest light spot on the measurement object. These properties open up numerous application fields for the sensors in factory automation, electronics manufacturing, robotics, or automotive engineering. Currently, Micro-Epsilon's product portfolio includes the Opto NCDT families 1220, 1320, 1420, 1900, 2300, and 5500. These sensors are available based on various technologies such as blue laser, laser line, and long-range laser.

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Laser triangulation sensors—often referred to simply as laser sensors—are primarily used for measurements requiring high accuracy and resolution. The measurement principle of laser triangulation is based on a simple geometric relationship. A laser diode emits a laser beam directed at the measurement object. An optic on a receiving element captures the reflected radiation. The distance to the measurement object can then be determined via the triangular relationship between the laser diode, the measurement point on the object, and the image on the receiving element. Depending on the object's surface, the reflected radiation is more or less intense.

Precisely Detect Even Small Parts

The optical principle allows measuring distances ranging from a few millimeters to over one meter (About 1/8 inch to over 3 feet), depending on the design. Laser optical displacement sensors measure from a relatively large distance to the object and with a very small light spot, enabling the measurement of extremely small parts. The distance to the measuring object also allows measurements against critical surfaces, such as very hot surfaces.

Sensors in the Opto NCDT series are equipped with various interfaces, including RS422 as well as EtherCAT, Profinet, and EthernetIP via an external interface module. The Opto NCDT 1220 model series now also features an IO-Link interface. Sensors in the Opto NCDT 1220 series offer high measurement accuracy and are particularly suited for displacement, distance, and position measurements in OEM and series applications in automation technology. They deliver precise measurement results with a measurement rate of up to 2 kHz. Thanks to Active Surface Compensation (ASC), the distance signal is stably regulated regardless of the color and brightness of the measurement object.

Interface With Numerous Advantages

IO-Link is a fieldbus-independent interface that enables manufacturer-independent, digital, and bidirectional point-to-point communication. IO-Link devices can be connected to the IO-Link master via 3-wire connectors and integrated into all common fieldbus and automation systems. To make data from the IO-Link level usable in higher-level systems or cloud-based services, IO-Link masters are used, which perform protocol conversion according to predefined rules. Users benefit from low costs due to simple installation, minimal programming effort through predefined function blocks, and quick commissioning. Additionally, troubleshooting can be simplified with consistent diagnostic information down to the sensor level.

IO-Link devices can provide information about the device status at any time. An error message provides clues about the cause of the issue. This enables users to narrow down the problem in the system more quickly or optimize the sensor's settings for the given measurement object.

Measure Board Profiles With the Highest Precision

An application example for Micro-Epsilon sensors with high speed and precision in confined spaces is measuring board contours. In a sawmill, the tree trunk, stripped of its bark, is first cut into boards using a frame, circular, or band saw. These boards still have what is called a wane on their narrow sides—the original surface of the round tree trunk. In the subsequent edger, the wanes are to be removed. Depending on the position of the board within the original tree trunk, the wane is flatter or steeper, and the board itself is wider or narrower. To achieve the highest possible yield during edging, the width of the wane must be determined so that it can be sawed off at the appropriate width. If too much is cut, valuable material is wasted; if the cut is too small, remnants of the wane will remain on the finished board.

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To address this task, sawmill operators use the Opto NCDT 1220 laser sensors with IO-Link from Micro-Epsilon. The challenge: Particularly when the wood is wet, it becomes shiny, which poses difficulties for conventional optical sensors. The boards enter the edger transversely and are measured during the process. Every 12 to 20 inches, an Opto NCDT 1220 sensor with a 8 inches measuring range is installed to measure the profile of the board in the transverse run. By default, the measurement is performed from above. Optionally, the edger can also be equipped with optical sensors on both the top and the underside, allowing the position of the boards—wane up or down—to be freely chosen. Thanks to the advanced IO-Link interface, sawmill operators can also network multiple sensors and implement predictive maintenance.

Specifically Compensate for Surface Reflections

In this specific application, the Active Surface Compensation ensures rapid adjustment to varying reflections and allows for a smooth distance signal. Due to the saw cut and the so-called wane, constantly changing surfaces are created, ranging from glossy to matte to partially reflective, and from light to dark. The ASC ensures that the exposure time adapts to these conditions.

To determine the measurements, the laser sensor projects a red laser point with a wavelength of 26 microinches onto the target. The laser light is reflected at a specific angle and imaged onto a CMOS line within the sensor through optics. During a rapid transition from a bright to a dark object, insufficient light would initially reach the receiver matrix without ASC. Conversely, during a quick switch from a dark surface to a shiny object, the intensity would initially be far too high. In both cases, the result would be inaccurate or even unusable. For this reason, the Micro-Epsilon sensor uses ASC to adjust the exposure time and thus the intensity of the emitted light during the measurement task, ensuring that the reflection on the CMOS line remains in the optimal range. The sensor then calculates the distance values with micrometer accuracy. The determined values can be fed into the system and machine control as analog or digital output signals.

Easily Integrate Sensors

The use of modern sensors—such as the laser triangulation sensors from Micro-Epsilon—increases quality and reduces waste, allowing companies to save on production costs. The compact design and integrated controller enable easy integration into machines and systems, even in confined spaces. Additionally, the IO-Link interface allows the sensors to be easily integrated into the field level.