The food industry poses significant challenges to the components — like sensors — used in the process technology. This means, for example, consistent hygienic design of parts in direct contact with the media. Also the requirements on the sensor technology are rising. In this case, the future belongs to smart sensors offering the user added value.
A great number of sensor s are necessary for the automation of processes in the food industry. The most important values to be detected are pressure, temperature, flow and level. The requirements on the respective sensors are similar to those in the process industry. Moreover, hygienic design is often absolutely necessary. In some applications it must also be possible to use sensors in hazardous areas.
Sensors With Added Value
A current example for sensor innovations is the LR level sensor operating to the guided wave radar principle. The sensor is installed vertically on the upper end of a tank and emits a microwave signal propagating downwards along the sensor probe. When the microwave hits the surface of the medium it is reflected back towards the sensor. From the transit time of the signal, the sensor determines the distance to the surface and thus the level in the tank. This measuring principle solves two difficulties which may occur when level measurements are carried out with other sensor types.
This particular sensor is insensitive to deposits on the tank wall or the probe, and even in case of viscous media the microwave propagates along the probe irrespective of the deposits. Alongside this, level measurement of liquids forming foam on the surface demand a great deal of the sensors. The type LR level sensor can even reliably detect the level in those applications. The level signal, which is influenced by the foam, is correctly evaluated by the sensor and the distance to the surface of the liquid is reliably detected.
The probe of the version for the food industry is made of high-grade stainless steel. Also the other parts of the sensor have a hygienic design and meet the requirements according to EHEDG. The user can exchange the probe and adapt the measuring range. Probes can be offered in different lengths from 150 mm to 2,000 mm. The probe can also be cut to length, if needed. This modular concept increases the flexibility for the user and reduces costs. The type LR level sensor is available with the IO-Link interface.
Communication Via Io-Link
Communication in times of Industry 4.0 becomes more and more important. The communication with the sensors is the first step to ensure continuous communication up to the company level. At ifm, the interface on the sensor level is IO-Link. All new sensors from ifm use this digital protocol in addition to the conventional analogue interfaces such 4…20 mA. As compared to the analogue transmission the measured value cannot be distorted by interference on the cable. Moreover, different values from one single sensor can be transmitted simultaneously (see box) adding even more value to the user.
Also for maintenance and repair tasks the user can benefit from sensors with IOLink interface. Since the sensors can be configured via IO-Link, the configuration can be transferred directly to the new sensor in case of replacement. Timeconsuming setting of the sensor on site is no longer necessary and the interruption to production is very short. Via IO-Link the user can even access the self-diagnostic data of the sensors and the faulty sensor can be quickly found. This will also increase the plant productivity.
Data Transmission To An Erp System
Another important aspect of the digital sensor communication is the possibility to use sensor data additionally for higherlevel ERP systems on the company level. For such tasks, ifm uses the Linerecorder. The Linerecorder Agent Connectivity Port, for example, is a software gateway allowing bidirectional communication between a great number of different interfaces. This allows communication between ERP systems and data from devices at the field, control and process control level.
The Linerecorder sensor allows the capture and transmission of any data especially for IO-Link sensors. With this system the data can be transmitted directly to the ERP system without an additional PLC in the automation solution being loaded. This direct path for sensor data by omitting the control level is referred to as ‘Y communication’ in ifm terminology because, splitting up like the letter Y, the data reaches, on the one hand, the PLC, and, on the other hand, the company management level.
This solution offers possibilities which are hard to implement with conventional sensors and analogue interfaces. Data logging, condition-based maintenance and improvement of energy efficiency are just some of them.
The Future Belongs To Smart Sensors
Smart sensors offer many advantages in applications in the food industry and help to reduce costs. Even if today many automation solutions still process analogue sensor signals, the distribution of sensors with IO-Link interface strongly increases. The added value provided by these sensors on different levels convinces more and more customers to switch over to digital communication.
Temperature Measurement With Added Value
A typical example for a sensor offering the user added value is the TAD temperature sensor. It features two different sensor elements operating independently from each other. The two sensor elements — Pt1000 and an NTC thermistor — have inverse temperature characteristics. A microprocessor integrated in the temperature sensor evaluates the signal of both sensor elements and checks the measured temperature value for plausibility. The TAD provides the result of the internal drift monitoring via a separate diagnostic output. Both measured temperature values, the differential value as well as the diagnostic value, can be transmitted via IO-Link.
With this sensor the prescribed regular calibration of temperature sensors is no longer necessary. Especially in the food industry where some processes require that the prescribed temperatures are exactly adhered to, the costs for external calibration can be saved.