Smart sensors are advanced measurement devices equipped with integrated processing capabilities and other features that enhance their functionality and reliability. While traditional sensors simply convert physical phenomena into electrical signals that can be recorded and processed, smart sensors can preprocess the data to provide instantaneous results.
In addition, they frequently include advanced features such as stored calibrations, internal diagnostics, and error correction algorithms. Flexible communications facilitate integration with various data logging and IoT platforms, while low power consumption allows for use in a wide range of applications.
Smart Sensor Applications
With their enhanced capabilities, smart sensors are utilized in a broad range of applications across many different fields. Some examples include:
- Environmental Monitoring: Smart sensors play a critical role in tracking environmental parameters such as air and water quality, as well as soil and weather conditions for research and effective resource management.
- Sea State Monitoring: Wind, waves, and currents can be measured with smart sensors to provide real-time sea state information in marine environments that can help to ensure safety for boat and ship traffic.
- Agriculture: In precision agriculture, smart sensors monitor soil moisture, temperature, humidity, solar radiation, and other factors to optimize irrigation, fertilization, and pest control, resulting in increased crop yields.
- Aquaculture: In aquaculture, smart sensors monitor water quality parameters such as temperature, dissolved oxygen, pH, and salinity to help maintain optimal conditions for fish and other aquatic organisms, thereby increasing productivity.
- Smart Cities: Smart sensors are a critical component in the development of so-called smart cities by monitoring conditions such as traffic flow, air pollution, energy consumption, and water levels at flood control infrastructure.
These are only several examples of smart sensor applications, but nearly every type of environmental measurement system relies on smart sensors for dependable data.
In non-telemetric systems, data collection instruments must be connected to a computer in order to download and access data.
Sensor Interfaces
Smart sensors interface with data loggers and control systems through various communications protocols. These interfaces offer standardization for seamless integration into sensor networks and data management systems.
In the context of environmental smart sensors, various digital and wireless interfaces are commonly used. Traditional analog outputs such as voltage or current signals are also still used in some sensor designs. However, this is typically for compatibility with legacy systems, and additional features like analog-to-digital conversion are often included.
Digital Sensor Communication Standards
Many sensor types utilize serial connections for data output. RS-232 is a common, widely supported hardware standard for serial communication that allows the transmission of data over relatively short distances. For serial communication over larger distances and/or noisier environments, RS-422 and RS-485 standards are often employed.
SDI-12 is another standard that was specifically developed for environmental sensors. Short for Serial Digital Interface at 1200 baud, it is a streamlined, power-efficient protocol for communication with SDI-12 smart sensors. Each device in a system is assigned a unique SDI-12 address for communication along the same bus in a multi-drop topology, meaning that multiple devices can communicate over a single line.1
Like SDI-12, Modbus RTU (Remote Terminal Unit) is an addressable protocol commonly used with environmental smart sensors. It also uses serial communication, most often over RS-485, because it supports long-distance, robust communication and multi-drop topology. Individual sensors are addressed from 1 to 247 (up to 255 in special cases), so it is an ideal choice for supporting large sensor networks like temperature profiling strings.
Modbus TCP/IP (Transmission Control Protocol/Internet Protocol) is a variant that is also useful in some cases. It uses Ethernet for communication, thus allowing it to work over standard network infrastructure at high data rates.
NMEA (National Marine Electronics Association) is a standard primarily used for marine and environmental data communication. It facilitates the exchange of data between marine instruments like GPS, sonar, and weather sensors, ensuring compatibility and interoperability across equipment from different manufacturers.2
These represent only a subset of the available communication technologies and protocols, but these are some of the standards most commonly used for environmental data collection systems with cabled sensor connections.
Wireless Sensor Communication Standards
Increasingly, sensor systems are relying on wireless technologies for communication. This can be separated into wireless communications for configuration/direct data download to a nearby device and for data transfer to data logging and management systems.
Configuration and direct data download refer to the initial setup of the sensor and manual data collection for standalone (non-real-time) logging systems. Bluetooth is a popular choice for sensor interfacing due to its short-range connectivity, low power consumption, and availability in many mobile devices, including smartphones, tablets, and field laptops.
Other options that are sometimes used for short-range connectivity include Wi-Fi, Wi-Fi Direct, NFC (Near Field Communication) and Infrared (IR) communication.
In permanent installations with wireless data transfer to data logging and management systems, various radio standards are common. These include protocols like Wi-Fi, LoRaWAN, Sigfox, NB-IoT, and Zigbee, which will be discussed in more detail in the Telemetry chapter.
Illustration of a pole-mount monitoring system equipped with a groundwater measurement instrument, weather station, anemometer solar panel, and X3 data logger
Conclusion
Modern smart sensors represent a significant advancement in environmental measurement technology, combining traditional sensing capabilities with advanced features to optimize performance and data quality. By leveraging flexible communication protocols, smart sensors can be seamlessly integrated into various data logging and IoT platforms, while power-efficient operation allows them to be applied to a wide range of use cases and environments.
Overall, the versatility and efficiency of smart sensors make them indispensable tools in modern environmental monitoring and resource management.
Resources
- SDI-12 Support Group. (2019, January 10). SDI-12: A serial-digital interface standard for microprocessor-based sensors – Version 1.4. Retrieved from https://www.sdi-12.org/archives_folder/SDI-12_version-1_4-Jan-10-2019.pdf
- National Marine Electronics Association. (n.d.). NMEA 0183 Standard. Retrieved from https://www.nmea.org/nmea-0183.html