Data acquisition
Data acquisition is the process of sampling signals that measure real-world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the acronyms DAS, ''DAQ, or DAU,'' typically convert analog waveforms into digital values for processing. The components of data acquisition systems include:
- Sensors, to convert physical parameters to electrical signals.
- Signal conditioning circuitry, to convert sensor signals into a form that can be converted to digital values.
- Analog-to-digital converters, to convert conditioned sensor signals to digital values.
There are also open-source software packages providing all the necessary tools to acquire data from different, typically specific, hardware equipment. These tools come from the scientific community where complex experiment requires fast, flexible, and adaptable software. Those packages are usually custom-fit but more general DAQ packages like the Maximum Integrated Data Acquisition System can be easily tailored and are used in several physics experiments.
History
In 1963, IBM produced computers that specialized in data acquisition. These include the IBM 7700 Data Acquisition System, and its successor, the IBM 1800 Data Acquisition and Control System. These expensive specialized systems were surpassed in 1974 by general-purpose S-100 computers and data acquisition cards produced by Tecmar/Scientific Solutions Inc. In 1981 IBM introduced the IBM Personal Computer and Scientific Solutions introduced the first PC data acquisition products.Methodology
DAQ hardware
DAQ hardware is what usually interfaces between the signal and a PC. It could be in the form of modules that can be connected to the computer's ports or cards connected to slots in a PC motherboard or in a modular crate. Sometimes adapters are needed, in which case an external breakout box can be used.DAQ cards often contain multiple components. These are accessible via a bus by a microcontroller, which can run small programs. A controller is more flexible than a hard-wired logic, yet cheaper than a CPU so it is permissible to block it with simple polling loops. For example:
Waiting for a trigger, starting the ADC, looking up the time, waiting for the ADC to finish, move value to RAM, switch multiplexer, get TTL input, let DAC proceed with voltage ramp.
Today, signals from some sensors and Data Acquisition Systems can be streamed via Bluetooth.
DAQ device drivers
DAQ device drivers are needed for the DAQ hardware to work with a PC. The device driver performs low-level register writes and reads on the hardware while exposing API for developing user applications in a variety of programs.Input devices
- 3D scanner
- Analog-to-digital converter
- Time-to-digital converter
Hardware
- Computer Automated Measurement and Control
- Industrial Ethernet
- Industrial USB
- LAN eXtensions for Instrumentation
- Network interface controller
- PCI eXtensions for Instrumentation
- VMEbus
- VXI
DAQ software