For companies in the field of industrial measurement and control technology, the topics of 'horizontal and vertical integration' offer particularly interesting starting points when it comes to Industry 4.0. The former is primarily about improving communication at fieldbus level: sensors must become 'smart' and be able to do much more than just reliably record and transmit measured values. For example, electronics integrated into the sensor not only simplify commissioning and calibration on site, they also make it possible to record and evaluate the entire life cycle of a sensor. Recording and comparing all this data in an industrial cloud can provide important insights for future sensor developments in the next step. But what characterizes such a smart sensor?

One fact always remains the same with physical sensors: the actual sensor element in which the physical or chemical measured variable is recorded is and remains an analog piece of technology that follows the physical properties of its measuring principle. It is only through the further processing and amplification of the analog signal in an electronic system that the physical effects are turned into usable measured values. But is that already 'smart'?

Even if the physical signals are converted in digital electronics, nothing 'smart' has happened apart from another form of signal conversion. However, if such sensors are connected to modern but separate measuring amplifiers, additional functions can be implemented: processing several sensors, performing calculations, monitoring plausibility, generating error messages, sending messages and even transmitting data to the internet or a cloud.

No Industry 4.0 without smart sensors

The system structure of 'Digiline': sensors for different measured variables can be connected to smart networks using so-called 'hubs'. This saves time during cabling and commissioning.

© Jumo

In the new generation of 'smart' sensors - thanks to the ever-increasing integration density of electronic components and the increased computing power of even the smallest microprocessors - this additional work of the measuring amplifier is moved closer to the original analog sensor element or integrated into the mechanical body of the sensor.

The advantages are obvious: less wiring is required, possible measurement errors are minimized and there is no need for special measuring amplifiers for each measured variable. Instead of analog measured value transmission, digital interfaces can now also take over communication at the sensor.

Such a 'smart' sensor becomes an independent system component. If its firmware - the sensor software - is designed accordingly, it stores its individual calibration data, its stress data (i.e. minimum and maximum values) and limit value violations, it performs calculations and linearizations and, if necessary, even reports possible errors in advance. In bus systems, such a sensor can register itself automatically in the system and be replaced more easily. Such independent and predictive action by the sensor can certainly be described as 'smart'.

Digital networks for liquid analysis

Two examples illustrate how Jumo implements the topic of 'smart sensors' in practice.

The first example - the 'Digiline' system developed in-house - comes from the field of liquid analysis. As a bus-compatible connection system for digital sensors, it enables the creation of intelligent sensor networks. This means that all important measurement parameters for liquid analysis can be measured with just one system. The highlight here is that the Digiline pH and ORP sensors are supplied as a unit consisting of a sensor with reusable electronics. Only when the pH or redox component is finally worn out is the connection disconnected and the electronics can continue to be used with a new sensor.

The Digiline sensor network extends the number of sensors that can be connected to the 'Aquis touch' multi-parameter measuring and control devices. In addition, the sensors can be integrated directly into the 'mTron T' automation system from Jumo, i.e. without an additional transmitter.

A wide variety of sensors can be connected together in a star or tree structure; only a single digital signal line then goes to an evaluation unit or controller. This enables efficient and fast cabling of systems in which several parameters need to be measured simultaneously at different points.

As most Digiline sensors are also available with a 4 to 20 mA analog output, it is also possible to integrate the smart sensors into older systems.

Thanks to the DSM (Digital Sensor Management) software included with the system, the necessary parameterization and calibration of the pH or ORP probe can be carried out in the laboratory using a PC or laptop, a USB interface converter and the Digiline software. Calibration data and the evaluation of the sensor status are stored directly in the sensor and enable complete documentation over the entire life cycle.