Introduction to Data Acquisition
The Evolution of DAQ Systems for Testing and Measurement
Aug 18, 2008
Data acquisition is the practice of collecting and storing data from sensors or other measurements equipment. Technically, data acquisition techniques could include manual monitoring and recording methods, such as visually inspecting a device or measuring an object, but it generally refers to the use of electronic sensors and data collection equipment.
Evolution of Data Acquisition Equipment
Prior to the use of computerized hardware, data was often recorded on paper. Strip chart recorders and plotters would take an input signal and convert that signal to the one or two dimensional motion of a pen on a sheet or roll of paper. It was up to the operator to calibrate the scale of the output recordings on the graphs to accurately reflect the behavior being monitored.
The next generation of data acquisition equipment included dataloggers, which were electronic systems that could store electronic from connected sensors and then either replay that data later via a paper chart recorder or by connection to a computer, such as a serial cable. Some dataloggers evolved to include floppy drives so data could be recorded to a floppy disk then transferred to a computer.
Finally, the advent of computer-based data acquisition allowed users to perform complex measurements and to store and retrieve data electronically. Data acquisition hardware was originally purely analog, requiring an analog-to-digital converter so the data could be stored digitally. Today, many data acquisition systems have the hardware to process signals. However, most sensors still function on a purely analog basis, so analog hardware capabilities are not expected to disappear anytime soon.
Data Acquisition Terminology
Like many disciplines, data acquisition systems and techniques have some unique terminology. Some of the more prominent terms include:
- Excitation – Excitation is a voltage or current input into a sensor. The sensor reacts in some way to the input and produces an output voltage or current that is measured by the data acquisition system.
- Gain – A gain circuit boosts the voltage of very low level signals so that they can be separated from background noise
- Sample Rate – The sample rate is the number of data points collected per unit of time. A fast phenomenon such as automobile collision testing requires very high sample rates to properly characterize the phenomena.
- Signal Conditioning – Signal conditioning is additional processing that is performed on a data signal to improve its quality
- Signal-to-Noise Ratio – This ratio is the comparison of the amplitude of a data signal over the amplitude of the background noise in the data. The larger the ratio, the less likely the data will be lost within the noise.
- Transducer – A transducer is another name for a sensor
Data acquisition is a vital tool for engineers to understand how systems function, and is an important part of system monitoring and safety testing.
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