Ethernet-enabled measurement technology has arrived in industrial production. Micro-Epsilon provides a few real-life examples to show the benefits of this technology.
Nearly 40 years ago the Ethernet network protocol was developed to ensure that data packages could be transmitted securely via unsecured communication media (cable, radio). This technology is based on combining a data package (frame) with a 32-bit checksum which the sender creates and the receiver verifies. If the received checksum is not the same as the calculated checksum, the data block is rejected and requested again. Today, when users hear Ethernet they don't just think of a data protocol but also of hardware: cables, routers, network adapters etc. Distribution of Ethernet has influenced the development of various cable types, resulting in today's twisted-pair cable.
What are the main reasons that make this technology so successful? Ethernet is an open protocol. It allows for nearly unrestricted flow of communication among networks, independent of the terminal device's operating system and any hardware used. This is how wi-fi technology connects wired and wireless systems. The operator can address the controller from anywhere using IP. He can then analyse the measurement data and perform remote maintenance from any location in the world. Operation and system configuration are performed through a standard web browser, no additional software is required. Data transmission via Ethernet is very fast: current technology allows for data rates of up to 10 Gbit/s. The data protocol ensures complete and error-free transmission. Any standard components used are mass-produced.
Low cost help to make Ethernet available in automation. An open Ethernet interface simplifies sensor integration into existing systems, the wiring effort is minimal.
Benefits of Ethernet-enabled measurement technology at a glance:
- measurement data can be analysed independent of location
- global remote maintenance
- no additional software installation required
- data rate of up to 10 Gbit/s
- secure data transmissions
- low-cost standard components
- simple integration into existing systems
- low wiring effort
However, other data transmission methods are also used for automation of machines and production systems.
Alternative methods
Field bus systems such as Profinet and K-Bus are alternatives to Ethernet for transmitting data between sensor and controller in networks. They are still widely used in automation technology. However, as Ethernet is now used for industrial purposes, for telecommunication and in homes, it has a few distinct advantages: very inexpensive hardware thanks to mass production and rapid availability of components.
Another type of data transmission system is the Universal Serial Bus (USB). Data acquisition systems with USB connections are compact, and power is supplied from the PC or notebook via a USB cable. USB works with a very high data rate and guaranteed transmission bandwidth. For industrial applications, however, USB is often not the best choice: compared with USB interfaces, Ethernet shows higher reliability. In addition, Ethernet allows for longer cables and a higher bandwidth. And no driver installation is required to detect external devices (sensors).
Application examples
Industrial production stands out through its size: systems worth millions of Euro, production halls the size of a soccer pitch and intricately woven workflows. The result is a cable jungle. It is complicated to integrate new sensors under these conditions. A measuring system with a multi-channel controller saves a lot of work, time and money. The universal controller CSP2008, for example, is a flexible solution for machine and system automation in a dynamic industrial environment. CSP2008 computes up to six sensor signals: two sensors are connected directly to the controller via RS422 interface or EtherCAT. Another four are linked to the controller through modular connections using separate EtherCAT modules. For multiple sensor applications, such as height measurements, coplanarity measurements, flatness and roundness measurements, signals are computed within the controller. CSP2008 is realtime-enabled up to 100 kHz. Measurement values can be checked locally on the controller. (Remote) operation is performed via a web browser interface directly from your working environment. No additional software is required in addition to the user interface (such as Mozilla Firefox browser).
In contrast to a production setting, laboratory or quality assurance departments require more flexibility, as working environments and sensors change frequently. The eddy current measuring system eddyNCDT 3100 is excellent for use in quality assurance, test labs and development environments, for example for quality control in spindle production. As spindles of various lengths and diameters are produced, sensors with different measuring ranges are required to ensure optimum measurement results. The smaller the measurement range, the more accurate is the detection of thermal expansion, deflection etc. As parameters and required values for ferro-magnetic and non-ferro-magnetic materials are stored in the sensor itself for eddy current displacement sensors of the eddyNCDT 3100 series, sensors can be reconnected to the same controller easily and without re-calibration. The measurement system is operated directly from the PC via an Ethernet interface.
In certain cases, Ethernet-enabled sensors even make it possible to switch from manual to automated procedures, for example in medical laboratories. Here active agents are manually filled into microtiter containers for batch testing. It is essential, but challenging to measure each agent precisely. Typically random samples are measured, but this is not sufficient for 100% quality control. Confocal measurements are a great solution for such applications. During confocal chromatic measurements lenses are used to separate white light into different spectra which is then focused perpendicular to the object. A spectrometer is used to transmit the reflected light to the CCD array: each position in the CCD array now corresponds to one wavelength, i.e. the distance between target and sensor. This technology facilitates measurements with a resolution of nanometer accuracy. For a long time no Ethernet-enabled controller was available for these sensors. They had to be connected to the PC using an A/D converter. The first controller with Ethernet interface was confocalDT 2451, it was launched in 2011 and opened up new applications for this highly precise type of measurement technology. In our example, the non-contact measurement system successively scans the microtiters in the plate and calculates the filling level through displacement measurements between sensor and liquid. Models and numbers of sensors may vary.
Individual sensors with integrated controllers are often used during production. Measurement values can be synchronised using Ethernet, for example in rock wool production. Rock wool is frequently used to insulate houses. To ensure that the required thermal properties are maintained, a specific thickness is vital. Laser triangulation sensors are used to control thickness. The highly dynamic sensor optoNCDT 2300 performs non-contact displacement measurements by analysing the reflected laser beam. In production, rock wool is manufactured to much wider and thicker specifications than the required size. After production, the sheets are trimmed and milled to the required thickness. This step produces unnecessary waste and is an additional load for milling tools. To optimize production efforts and reduce waste, sheet thickness is measured before the cutter using two optoNCDT 2300 laser triangulation sensors. They work at speeds of up to 49 kHz which makes them suitable for in-production quality control. The thickness is calculated based on the distance from the rock wool to the the sensor and the support. The sensors measure each sheet from above and from below. They are connected to the PC via EtherCat. The thickness of the rock wool is calculated from the difference between the two measurement values. High bandwidth and high data transmission speeds via Ethernet enable synchronicity of data logging.
Outlook
Ethernet network technology convinces through reliability, high data transfer rates, easy integration into existing networks, and low hardware cost. No other bus system has developed as dynamically and offers as much future potential. Micro-Epsilon builds on these benefits and is going to introduce further Ethernet-enabled measuring systems onto the market in future. In addition to the sensor models mentioned above, the sensor technology expert offers capacitive measurement systems, laser profile scanners and inline colour measurement systems with Ethernet connections.
