Pressure and Level Measurement in the Internet of Things System

Everyone around talks about moving towards full digitalization. But how will you embark on this path and which direction is right for your company? KELLER AG für Druckmesstechnik has over 45 years of experience in recording and processing measurement data. Our range of services, from pressure sensors to a ready-made web application, will help you find your way to a customized control system solution via the Internet of Things.

Industry 4.0 and Smart City are revolutionary technologies behind the digitalization of pressure sensors and pressure measurement solutions. At the core of digitalization lies the intention and necessity to increase process efficiency.

The path to digitalization begins with data recording, mainly using sensors. Pressure sensors also record measured values. For equipment or containers and tanks, they display fill levels. For lakes, rivers, and groundwater, levels are measured. The measured objects are connected to the Internet, store their data in the cloud, and this data is mostly transmitted wirelessly via radio transmission. The latest technologies such as LoRaWAN or mobile communications (NB-IoT, LTE-M) are also used. Ultimately, data can be received on all possible end devices such as computers, tablets, or mobile phones. This entire internet environment, consisting of objects and their connections, is called the Internet of Things.

Internet of Things Service Suite

KELLER AG für Druckmesstechnik offers this comprehensive solution, as described above, in the form of a measurement system via the Internet of Things. This type of measurement system allows the user to take a direct step towards digitalization with minimal effort and low costs:
• No need to create software or hardware solutions.
• Access to a working and proven measurement data recording system.
• No separate technical training in technology required.

The KELLER measurement system is designed so that each part of the measurement chain has a defined interface. Thanks to an open and documented cloud API (Application Programming Interface), the user can integrate the measurement data processing system into their own
information system and thus start exactly where the greatest benefits of digitalization unfold. KELLER provides access to all individual interfaces so that, from an implementation perspective, users have the freedom to choose whether they want to install the entire system or only part of it, if necessary.

How deeply this vertical integration will be involved depends on the application area and requires consideration of costs in comparison to benefits. The lowest level of integration is defined by the pressure sensor signal. The diagram below shows the individual levels of integration from the pressure sensor series 9L to the web application:

The user can independently integrate individual elements into their devices, and corresponding interfaces are available for this purpose.

You can test the Keller Internet of Things measurement system right now

Step-by-step digitalization including examples and KELLER products

1. Define data registration points / measurement points for proof of concept.

Available level measurement point

2. Choose a suitable pressure transducer based on requirements such as accuracy, media compatibility, etc.

Level transducer series 36XW for groundwater level determination

3. Select LoRaWAN or mobile communication transmission technology.

Remote data transmission unit ADT1-Tube for LoRaWAN or ARC1-Tube for mobile communication. 

Note: Check the network coverage zone at the measurement point for the chosen technology. Selected measurement points should be as close as possible to the person responsible for the system so that discrepancies can be found and corrected on-site in case of malfunction. Verification of the recorded measurement results should also be performed during work at the measurement site.

4. Manage the measurement points over several weeks and closely monitor them using graphical representation in the cloud.

KOLIBRI Cloud.

5. Expand the proof of concept measurement system with additional, possibly technically important measurement points and carefully monitor any discrepancies.

Level measurement points with poor signal reception or technical measurement issues

Current status: According to this extended concept, the entire system needs to be thoroughly analyzed and evaluated to determine whether the results meet expectations.

Up to this stage, the Keller Internet of Things measurement system could be used with minimal investment. Now it is necessary to assess whether to keep the system as is and accordingly complete the digitalization project, or if deeper integration of the system into the company's software is required.

6. Automatic data synchronization between the measurement system and the company's own cloud.

IPP 3 software interface.

Note: Providers of the company's own software often do not know how to generate Internet of Things measurement data. KELLER's many years of experience helps establish clear and specific functional requirements for the measurement data it records in the external system.

7. Full vertical integration. Sensor or pressure transducer, remote data transmission unit, KOLIBRI Cloud.

Open interfaces for all parts of the entire measurement chain

Digitization of the pressure sensor signal. Pressure sensor signals are processed and digitized using an electronic board. This means they are converted into a number (pressure) that can be read via an interface. In addition to pressure and temperature, other useful information can also be read from the pressure sensor.

In many cases, too little attention is paid at the initial stage of the process to the importance of accuracy, stability, and reliability of the sensor. The sensor that records data is one of the most important parts of the system because decisions made and actions taken are based on this sensor data:
• Turn off the device
• Fill the tank
• Too low groundwater level = signals no drinking water supply!
• Too high groundwater level = signals flooding!

Therefore, the sensor at the beginning of the entire measurement chain has the greatest impact on data quality and must be selected and designed according to the measurement system requirements.

KELLER offers specially designed and tested pressure sensors for the appropriate application and requirements. For using pressure sensors with own measurement data transmission equipment, KELLER provides communication protocols for RS485 or I2C interfaces. For applications intended to use the pressure sensor without a typical output signal, the sensor is supplied with calibration data.

Remote transmission. Another important part of digitalization is the transmission of recorded data. Often sensors are located in places remote from the central data collection and evaluation point, or sensors cannot be connected to a local communication network.

The Internet of Things is a global network that enables data exchange via the Internet. This means that sensor data, for example, obtained from different points around the world, can be combined in a single system (cloud). A mandatory condition for this function is that the device, instrument, or sensor has Internet access. As a measurement solution from KELLER, we use autonomous Internet of Things devices powered by batteries that transmit data via various radio interfaces.

One of the advantages is that these devices can be installed with minimal effort since there is no need to lay cables, and the measuring instruments do not need to be connected to the company's communication network. To ensure that the devices and their batteries have a long service life, along with an intelligent energy-saving electronic system, standard radio technologies (LoRaWAN, as well as mobile communications 2G, 3G, 4G, NB-IoT, LTE-M) with low power consumption and a long transmission range of 15 km or more are used. The choice between LoRaWAN or mobile communication depends on the data logging requirements or the radio coverage area available at the site.

In both radio systems, two-way data exchange is possible. This means that measured values can be sent not only from the measurement point to the central collection point (cloud), but communication from the central collection point to each measurement point is also possible. Communication with the device is used to configure notifications from the device, for example, when measuring intervals remotely. The communication interface of KELLER devices with LoRaWAN (ADT1), as well as devices with mobile communication (ARC1), is documented, and a sample code is available for integration into the company's device.

All devices are designed to allow software updates to be installed. This is very useful in practice for expanding radio technologies or modifying wireless protocols. The electronics of the ARC1 mobile communication device for data transmission have a modular design and allow the radio module to be replaced in case of future technological changes, so the transmission device can be adapted again to the latest generation of mobile communication with minimal intervention and without the need to replace the entire device.

Features of transmission via LoRaWAN

• Data exchange is carried out through gateways (antennas) connected to a network server via the Internet. Measurement data is transmitted from the network server to KOLIBRI Cloud, or the device accesses data from the network server. Individual measured values are transmitted at maximum short intervals of about 10 minutes.
• Transmission usually occurs without confirmation of success.
• When using LoRaWAN, transmission is carried out via public networks (often owned by mobile network providers), private networks (a city may have its own network), or open networks such as Internet of Things networks.
• Transmission range of 15 km or more, depending on site conditions.
• Operation without a SIM card / the transmission device must be registered on the network.
• Transmission via unlicensed radio frequency. Anyone can set up their own radio frequency.
• A global radio network (still) does not exist.

Features of transmission via mobile communication (2G, 3G, 4G / NB-IoT, LTE-M)

• Data exchange with KOLIBRI Cloud is carried out via standard technologies such as FTP or email; the technology used (2G, 3G, 4G / NB-IoT, LTE-M) does not matter.
• A large number of measured values can be recorded in a short interval (1 minute). Data is usually transmitted in data packets containing several measured values.
• Data is always transmitted with receipt confirmation. The converter will see whether the transmission was successful.
• Radio transmission uses only mobile network operator networks.
• Transmission range of 15 km or more, depending on site conditions.
• Operation with a SIM card.
• Transmission via licensed radio frequencies. These radio networks can only be used by mobile network operators.
• A worldwide communication system.

Security

For LoRaWAN and mobile communication, data from the measurement point to the cloud is transmitted in encrypted form. Modern encryption processes are used here. For mobile communication, encryption can be more reliable due to higher data processing speeds and the choice of available encryption types.

KOLIBRI Cloud from KELLER offers simple and convenient access to measurement data with your personal login and SSL encryption. With the KOLIBRI Cloud web application, data is available without the need to configure and maintain a database. Measurement data can be displayed graphically with minimal time expenditure, and the export function allows downloading data as Excel or CSV files. Measurement points are easily and promptly monitored using the built-in alert system. For example, if the water level rises or the battery discharges, a notification will be sent by email.

The cloud software interface (API) allows measured data to be output from another software system in a standard JSON format via HTTPS. Thus, data can be continuously transmitted to the company's own software system, making processes more efficient, which is the goal of digitalization through the Internet of Things.

KELLER provides software developers with detailed API documentation.