CAN bus data loggers
CAN bus data loggers are primarily used in industry. The Controller Area Network (CAN) bus is a serial fieldbus system that enables nonproprietary data sharing between devices. CAN bus data loggers feature simple setup, a wide range of configuration options and autarchic operation. This article explains what CAN bus data loggers can do and what benefits result from using them.
To enable different components of a technical system to communicate with each other, interfaces are needed. Information is transmitted via these interfaces. Until the 1980s, such interfaces were interconnected and interlinked with ever more complex cable harnesses. In a standard car of the time, such wiring harnesses could easily reach a total length of up to 2 kilometres. In 1983, the Bosch company worked with Intel to develop a new system to reduce wiring harnesses, thereby saving weight and costs. This system was named Controller Area Network: the serial bus system CAN began its triumphal march.
In bus systems, information is transmitted via a common data line from which individual, short spur lines branch off to the separate components. This setup reduces the amount of wiring while also easily allowing additional components to be subsequently connected. Since data transfer takes place via a common main line, a protocol needs to be integrated into the bus system. Such protocols control data transfers and direct data packets precisely to the relevant connected components. CAN bus systems use a 2-wire bus and an extra earth wire to connect the components.
CAN bus systems usually use two-core copper cables for data transmission. Alternatively, two extra cores can be used for the power supply and earth. Data transmission rates depend on cable length. The rule is, the higher the required data rate, the shorter the cables must be. The beginning and ending of each bus line are terminated with 120 Ohm resistors. Sub-D connectors are mainly used to connect individual components within a CAN bus system, but screw connections can also be used. Since 2003, CAN has been standardised according to ISO 11898.
CAN bus systems not only significantly reduce costs, but also provide high interference immunity and the capability of transmitting data in real time. The CAN bus is electrically immune to interference by means of "differential signalling". This means that one bit is sent in parallel on two lines with an opposite change in potential. If interference occurs, it affects both lines in the same direction. However, since the two lines have opposite levels, any difference between the two levels remains almost the same even in the event of interference. This "Common Mode Rejection Ratio" (CMRR) makes CAN bus systems highly immune to electrical interference.
Other benefits of the CAN bus:
- Speed: CAN bus systems enable data to be transmitted at high speed. This enables real-time applications, e.g. live monitoring of machinery and test stands.
- Easy to install: CAN systems require far fewer cables and are quick and easy to connect to each other.
- Reliable: The fewer connectors and cables in use, the fewer the possible sources of error.
- Cost-efficient: CAN systems make minimal demands on the hardware and signal processing, so procurement and operating costs are correspondingly low.
CAN logger is short for CAN bus data logger. Can loggers are data loggers that can be connected directly to existing CAN bus systems. This type of data logger is capable of processing different protocols making it very flexible in its applications.
CAN loggers can collect measurement data via the following protocols as well as others:
- OBD2 - Cars, HGVs, etc.
- J1939 - HGVs, tractors, forklift trucks
- CANopen - Plant and machinery, robotics
- DeviceNet - Automation
- ISOBUS - Agriculture
CAN loggers can, in principle, log any data that is sent in a controller area network. Common applications include speed monitoring of drive motors, temperatures of cooling lubricants and oils, fill levels and pressures. Delphin CAN loggers have a CAN bus interface that can be programmed as required. Any identifier can then be read, scaled, processed and stored.
Because CAN loggers are so flexible, they can be used in a wide range of applications. They are particularly suited to autarchic, mobile applications. Typical applications for CAN bus data loggers are:
- Transport systems
- Rack robotics
- Vehicles and aircraft
- Plant and machinery
- Vibration measurements
Delphin Technology has an extensive range of data loggers that can communicate via CAN bus. In addition to the Expert Logger the modular measurement, control and monitoring devices from the ProfiMessage series also have bus interfaces. The Expert Vibro from Delphin is a CAN bus-compatible data logger for vibration measurement. The Expert Transient is an autarchic data logger for synchronous recording of transient and periodic processes.
Data loggers used in measurement, control and monitoring tasks ideally require universal connection options. ProfiMessage D, a combination device from Delphin Technology, provides highly versatile fieldbus interfaces in a compact design. With internal control, regulation and monitoring functions, measurement values can be recorded and monitored simultaneously while regulation and control tasks can be processed autarchically. The ProfiMessage data logger features a programmable CAN bus interface, two separate PROFIBUS DP slave interfaces, Modbus TCP/RTU and RS232/RS485 connectivity to enable comprehensive monitoring and control of industrial processes and systems as well as measurement tasks in vibration analysis.
CAN bus data logger functions can be greatly extended by using the right software. The Delphin Data Center software provides users with centralised DAQ measurement data management. Data acquired by CAN loggers can then be interlinked, analysed and stored. The Delphin Data Center provides maximum performance in processing and providing data. It has the flexibility to be adapted to any measurement data management task without any programming being required. The Delphin Data Center is an efficient solution for state-of-the-art, high-performance measurement data management, whether in testing, plant and machinery monitoring or service life testing. Another advantage of the Delphin software is that it not only acquires data from CAN bus loggers, but can also store, export and view the information in a structured way with other data records. High flexibility is enhanced by options to process all existing CAN bus data in the measurement network, including data from third-party manufacturers or a PLC. The acquired data can also be exported clearly, quickly and at the click of a mouse and output to any standard mobile and desktop device.