18.07.2022
Data acquisition (often abbreviated as DAQ or DAS) is the process of sampling signals that measure physical phenomena in the real world and convert them into digital form that can be manipulated using computers and software.
Data collection is distinct from other forms of recording data into recorders or paper charts (data logger). The signals are converted from the analog domain to the digital domain and then written to digital media such as ROMs, flash media, or hard drives.
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What does the data collection system measure?
Data collection systems mainly serve the measurement of physical phenomena such as:
Note that there are several other measurement quantities, including light and image, sound, volume, location, speed, etc. that can be measured using a data acquisition system.
DEWESoft's easy-to-use DAQ system
Purpose of data collection
The main purpose of a data collection system is to collect and store data. But they are also intended to provide real-time data visibility and analysis and archiving. Furthermore, most data collection systems have some built-in report creation and analytics capabilities.
A recent innovation is the combination of data collection and control, in which the high-quality DAQ system is closely connected and synchronized with the control system according to
Some typical purposes:
Data logging
Data Retention
Real-time data visualization
Evaluate post-logging data
Analyze data using various calculations and statistics
Create a report
Data collection equipment is also heavily used in surveillance applications. Examples are:
The importance of data collection systems
Data acquisition systems or DAQ devices are essential during the testing of products, from cars to medical devices – to any electromechanical devices people use.
Before collecting data, the products were tested in an unstructured, highly subjective way. For example, when testing new suspensions in cars, engineers often rely on the opinions of test drivers about how the suspension feels to them.
With the invention and development of the data acquisition system, which made it possible to collect data from a variety of sensors, these types of subjective opinions were replaced by objective measurements. These can easily be repeated, compared, analyzed mathematically, and visualized in many ways.
Example of extreme load test case on truck with DEWESoft
Today, no one wants to build any type of vehicle, big or small, aircraft, medical devices, large-scale machinery, etc. without using data collection to objectively measure their performance, safety, and reliability factors.
Measurement process
Data collection is the process of converting real-world signals to the digital domain for display, storage, and analysis. Because physical phenomena exist in the analog domain, i.e. the physical world in which we live, they must be first measured there and then converted to the digital domain.
This process is carried out using a variety of sensors and signal conditioning circuits. The outputs are sampled using analog-technical converters
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Components Sensors, probes in a measurement system
The measurement of physical phenomena, such as temperature, the level of a sound source or vibration that occurs due to constant movement, begins with the sensor. The sensor is also called an adapter. A sensor converts a physical phenomenon into a measurable electrical signal.
Several types of sensors were invented to measure typical physical phenomena:
Force cell: for measuring weight and load
LVDT sensor: LVDT is used to measure displacement
Depending on the type of sensor, its electrical output can be voltage, current, resistance, or another electrical attribute that changes over time. The output of these analog sensors is usually connected to the input of the signal conditioner.
Signal conditioning
Signal harmonics are working in taking output from analog sensors and normalizing them for inclusion in an A/D converter.
For example with a temperature measurement system. The signal conditioning circuit needs to linealize the output from the c sensor
Each signal conditioning circuit is designed by the manufacturer to perform element normalization of the sensor output to ensure its linearity and fidelity to phenomena, and to prepare for digitization. And since each type of sensor is different, signal regulators are required to match those sensors.
Galvanic Isolation
Electrical isolation is the separation of a circuit from other potential sources. This is especially important with measurement systems because most signals exist at relatively low levels, and external potentials can greatly affect signal quality, leading to misreadings. The interfering potential can be both AC and DC.
For example, when a sensor placed directly on the item being tested, (e.g. a power source) has a terrestrial potential (i.e. not at 0V), this is possible
Filter
Almost every signal that we want to measure can be affected by electrical or other interference. This has many causes, including ambient electromagnetic fields that can be formed into high-gain signal paths or simple potentials that exist between the sensor or measurement system and the object being tested. Therefore, the best signal conditioning systems provide selectable filters that engineers can use to eliminate these interferences and make better measurements.
Some basic types of signal filtering
Analog-Digital Converter (ADC)
The output of most physical measuring signal harmonics is analog. It is necessary to convert this signal into a series of high-speed digital values so that it can be displayed and stored by the data acquisition system. Therefore, ADC is used to convert this signal.
There are many types of ADCs, including multiplexers and single converters per channel. In a multiplexed ADC system, a single analog-to-digital signal converter is used to convert multiple signals from analog to digital domain. This is done by pairing each analog signal into the ADC.
This is a lower-cost approach than having an ADC chip on each channel. But on the other hand, it is impossible to accurately align the signals on the time axis, since there are only
The signal conversion rate is called the sampling rate. Certain applications, such as most temperature measurements, do not require high speeds because measurement quantities do not change too quickly. However, alternating voltage and current, shock and vibration, and many other measuring quantities require sampling rates in tens or hundreds of thousands of samples per second or more.
An ADC with a resolution of 16 bits can theoretically digitize signals with a resolution of 65.535 (2^16 = 65.536) and with an ADC of 24 bits h
Data Visualization and Visualization
One of the most important functions of any DAQ system is the ability to visualize data in real-time during data storage.
Waveform data can almost always be displayed as a Y/T waveform based on a graph or grid and in numerical form. However, other graphical conventions can be added, such as bar graph form, FFT (Fast Fourier Transform) frequency/intensity graph, etc.
Today's most versatile DAQ systems
Data analysis
The data collection system provides an important, visual reference of the status of the test in real time. But once stored in a DAQ system, the data can also be analyzed using tools built into the DAQ system or third-party data analysis software.
As mentioned earlier, nearly every DAQ system on the market today has some sort of built-in data export filter to convert the system's proprietary data format to a data format
See more DAQ types here.
