Selecting the Right Data Logger

Learn how to select the right data logger for your data-logging system. With NI C Series hardware, you can choose from several different implementations for a data logger, whether it is USB-powered from a computer or runs remotely with stand-alone storage and Ethernet connectivity.

National Instruments C Series data loggers combine rugged, modular hardware with flexible software to easily implement a variety of data-logging applications. With more than 40 hot-swappable modules to measure virtually any sensor, USB or Ethernet connectivity options, and UL certification for hazardous locations, a C Series data logger works for any sensor and any project. 

Overview and Comparison of C Series Hardware 

Three Levels of Data-Logging Software from National Instruments

What is a data logger?

Many people and companies define the term “data logger” in slightly different ways. For these purposes, assume that a data logger always results in an electronic data file on some form of storage media. Data loggers contain three main components: 

1. Signal conditioning for the sensor or signal type such as cold-junction compensation for thermocouples, excitation for RTDs, or bridge completion for strain gages.
2. Analog-to-digital conversion through an ADC of some set resolution.
3. A computer or processing element. Even in the case of very small, inexpensive, stand-alone loggers, there is a processing element on board that takes data from the ADC and writes it to an electronic file. In most cases, the software or firmware on local data-logging devices is fixed by the vendor, leaving you with the job of uploading the file to a PC to perform any postprocessing, analysis, and reporting.

What should determine the setup or topology of a data logger?

There are several questions to consider when shopping for a data logger.

1. Can it take the measurements you need now and in the future?
   Data loggers should be viewed as tools for scientists, engineers, technicians, students, and anyone else working in a measurement environment. Selecting data loggers that easily expand can often save you money in the long run because you can avoid using multiple pieces of equipment for each project. With modular and expandable systems, you can purchase only the equipment you need now and buy more later as your needs grow.
2. How close is the closest computer resource (PC)?
   It is pretty safe to say that the electronic file from a data logger almost always ends up on a PC. This could be for full-time storage in a database, data processing, charting, or reporting for visual analysis and review. If the signals you are logging can be close to a PC, choosing a PC-based data logger can save you a step in the process by localizing, or even automating, that entire process. USB has usable ranges of 5 m on one cable or about 10 to 20 m with repeaters, and Ethernet has a range of 200 m between hubs and an install base covering most of the planet. The computer in question does not necessarily need to be dedicated to the data logger system. With the multicore processors available in PCs today, a decent-sized data logger program can run in the background and cause little to no interruption in normal use.
3. What is the environment to which this logger could be exposed?
   For some applications, such as road tests or in-vehicle tests, cabling to a PC may be a problem. For these cases, you can use a laptop or a data logger with embedded storage. In either case, you need to consider environmental specifications such as the operating temperature range, power supply needed by the data logger, and shock and vibration survivability. C Series products are built with a sturdy, metal housing and, in some configurations, operate in environments ranging from -40 to 70 °C. They also can sustain shocks up to 30 g. Learn more by reading the white paper, “Overview and Comparison of the C Series Hardware Family.”
4. How much software flexibility do you need?
   Almost all data loggers come with software. Sometimes it is built into the product, such as the data loggers with onboard memory, and sometimes it comes as an application for a PC to view live data. Either way, it is important to understand the capabilities and limitations of data-logging software. With data loggers built from C Series hardware, you can select the software that best suits your needs. In addition to the three levels of data-logging software from National Instruments, which offer interactive software with no programming required or a full graphical programming environment, you can program USB C Series data loggers with ANSI C, C++, C#, Visual Basic 6.0, and Visual Basic .NET, giving you ultimate flexibility when it comes to data acquisition and logging with your data logger.
5. Where will this data logger need to be installed?
   Mounting and connectivity is a bigger issue than most people think, and having something as simple as predrilled holes can mean large time savings when it comes to system installation and integration. All C Series multimodule chassis come with multiple mounting options including rack mount, DIN-rail mount, and flat panel mount. Dimensional drawings are available in both PDF and CAD file versions online. (Learn more about mounting options under the resources tab on chassis model pages.)

What are the advantages to NI C Series data loggers?

Hardware flexibility: With more than 40 modules to choose from, you can build a system that not only fits your unique channel and sensor needs now but also can grow and change in the future with minimal cost that is directly proportional to your channel-count or sensor-type modifications. In addition, you can expand your system or change the measurements in the same chassis without purchasing additional software. You can reuse, reconfigure, and reprogram the software to meet your new needs.

Software flexibility: You can program any piece of C Series hardware with NI LabVIEW software, which was designed to make developing data acquisition programs and data-logging systems easier while retaining the full functionality and flexibility of a programming language. C Series devices that can be programmed with NI-DAQmx, such as the single module carrier and NI CompactDAQ, are shipped with LabVIEW SignalExpress LE interactive measurement software as well as an API for programming in ANSI C/C++, C#, Visual Basic .NET, and Visual Basic 6.0.

The bottom line is you are not only buying a data logger for your current project – you are buying a powerful tool that you can put in your measurement toolbox.

1 ratings | 3.00 out of 5

Read in English Chinese (Traditional) French German Japanese Korean | Print | PDF

Reader Comments | Submit a comment »