Data Acquisition Information
Data Acquisition Computer Board | Rack Mountable Data Acquisition System | Data Logger
Data acquisition, referenced by the acronyms DAS or DAQ, is the digitizing and processing of multiple sensor or signal inputs for the purpose of monitoring, analyzing, and/or controlling systems and processes. Signal or sensor inputs define the behavior of physical parameters and come from devices such as sensors, timers, relays, and solid-state circuits. Internal circuitry is used to digitize and process these input in order to monitor, analyze and/or control systems and processes.
Types of Data Acquisition
Data acquisition is a broad area that encompasses several specific products. Products represented include: computer boards, instruments or systems, data loggers or recorders, chart recorders, input modules, output modules, and I/O modules.
|Chart recorders and strip charts are data acquisition tools used to generate a plot, graph or other visualization of data versus time. Each device is configured to produce one of several different types of charts including circular charts, strip charts, X-Y plotter charts, and paperless or video graphs.||
Image Credit: ABB Measurement Products
|Data acquisition computer boards are self-contained printed circuit boards (PCBs) that plug into backplanes and motherboards, or interface directly with computer buses. They receive multiple electrical or electronic inputs from devices such as sensors and translate analog data into a digital format that computers can process.||
Image Credit: ADVANTECH
|Data acquisition systems and instruments are configured in a wide variety of instrumentation and modular systems. They are generally packaged in an enclosure or chassis with a user interface and display. They collect, digitize, and process multiple sensor or signal inputs for the purpose of monitoring, analyzing, and/or controlling systems and processes.||
Image Credit: OROS
|Data loggers and data recorders acquire digital data from sensors and other signals. They are primarily used to store data for subsequent downloads to a host PC, but may also include real-time features such as monitors and alarms.||
Image Credit: Measurement Computing
|Data input modules receive signals from devices such as sensors and often provide voltage and current excitation along with signal conditioning. They are a front end device that interfaces with computer boards, systems, instruments, or recorders.||
Image Credit: PHOENIX CONTACT
|Data output modules transfer amplified, conditioned, or digitized signals to processing systems or devices. They are a backend device and the signal is a conditioned output from a computer board, system, instrument, or recorder.||
Image Credit: ACCES I/O Products, Inc.
|Data acquisition I/O devices have both input and output functionality. Digital or discrete I/O modules include on-off signals used in communication, user interface, or control.||
Image Credit: OPTO 22
Signal conditioners provide filtering, amplification, converting, and / or other processes required to make sensor outputs suitable for data acquisition. The signal conditioning process is also known as a transfer function because the final effect is to convert an input signal (or measurement) into a suitable output signal. For instance, when a temperature sensor measures the temperature of a system or environment, the output of the sensor (temperature) is not suitable to be an input signal to an electrical system. Therefore, the temperature measurement must be converted into an electrical signal.
The following diagram shows the evolution of a signal from the sensor through the central processing unit and to the output or load. More detailed information is available in GlobalSpec's Signal Conditioners Selection Guide.
The signal chain. Image Credit: Electronic Design
The conditioning of the signal can be handled by a signal conditioner, signal converter, or may be integrated within the module that receives the inputs or the device that takes the measurement. The amount of conditioning required is dependent on the carrier signal and transmission distance. A transmitter with an analog current output is generally required when transmitting a signal over extended distances.
An interface is used to transfer conditioned and digitized signal and sensor data to and from a system. Data acquisition products interface via a wide variety of field buses, computer buses, and other protocols. They may have a direct backplane interface, dock in modular bay or slot, or have a dedicated Ethernet, serial, parallel, wireless, or other port type used for interfacing with a host computer.
Image Credit: HUNG TA INSTRUMENT CO., LTD.
The function of the device is to monitor, analyze or control systems and processes.
Data acquisition devices used to monitor process and systems have the ability to record data points over a timed interval. They are customized for a particular application and may require specific modules in order to accommodate the type or number of inputs used. They may be equipped with on-board memory, removable storage, or may interface with a computer, used to process, store, and visualize the data. They may also be equipped with a switched output used to trigger an alarm or activate a switch when a pre-set condition is met or exceeded.
Monitoring with a virtual chart recorder. Image Credit: Newport Electronics, Inc.
Data acquisition hardware may be used for data analysis. Data points or real-time data can be fed into a system that reduces or compiles data in order to generate useful information. Fourier transforms are used to reduce a signal with respect to time into a series of sinusoidal terms. Application software is commonly used for signal processing and measurement functions.
Fast fourier transforms (FFT). Image Credit: The Register
Data acquisition products can be used to control processes and systems. The central processing unit receives a feedback signal and produces a switched output or analog control signal that is used to control devices in a system or process. Common applications include motion control, industrial automation, web processing, and other industrial operations. Supervisory control and data acquisition (SCADA) systems are large-scale, industrial control and measurement systems that consist of a central host, one or more remote units, a communications network, and specialized software. More detailed information about SCADA is available in GlobalSpec's Supervisory Control and Data Acquisition Systems (SCADA) Selection Guide.
Water Treatment - SCADA- Plant-IQ
Video Credit: mmassaNY
Related Products & Services
Current Loop Converters
Current loop converters convert an analog or digital signal to a current loop output such as 4-20 mA or 0-20 mA.
Current-to-voltage converters scale and convert current signal input to the desired output voltage range.
Data Input Modules
Data input modules accept sensor and other signal output for data acquisition systems. They may include signal conditioning prior to the analog-to-digital conversion stage.
I/O Modules and Instruments
Data acquisition I/O devices have both input and output functionality. Digital or discrete I/O modules include on-off signals used in communication, user interface, or control.
LVDT and RVDT Signal Conditioners
Linear variable differential transformer (LVDT) and rotary variable differential transformer (RVDT) signal conditioners are devices that translate the linear or rotary movement of a ferromagnetic armature into an AC voltage that is proportional to the armature position.
Sensor transmitters are measurement or signal conditioning packages that provide a standard, calibrated output from a sensor or transducer in the form of a current loop output (e.g., 4-20 mA).
Voltage Converters and Voltage Inverters
Voltage converters and voltage inverters accept voltage input and provide a scaled voltage output. Conversion types include scaling up a low-level signal, voltage doubling, and inversion (converting a positive voltage to negative and vice versa).