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What is Data Acquisition – DAQ?

Sampling and Digitizing Physical Signals

Data acquisition, or DAQ as it is commonly known, is the act of digitizing data from the surrounding environment so that it may be presented, processed, and saved on a computer. The measurement of a room's temperature as a digital value using a sensor such as a thermocouple is a straightforward example. Modern data collecting systems may incorporate data analysis and reporting software, network connectivity, and remote control and monitoring capabilities.

DAQ Components
The three main components of every data collecting system are the Sensor, Signal Conditioning, and Analog-to-Digital Converter (ADC).

Analog-to-Digital Converter

Analog-to-Digital Converters are the heart of all data acquisition systems (ADC). This chip, as its name suggests, converts environmental data into discrete levels that may be read by a CPU. These discrete levels represent the smallest discernible variation in the measured signal. The greater the number of "bits" (12-bit, 16-bit, 18-bit, etc.) of an ADC, the greater the number of discrete levels that can represent an analog signal and the higher the resolution of the ADC. The resolution of an ADC is comparable to the increments on a measuring tape. A measuring stick with mm tick marks offers greater resolution than one with cm tick marks alone. The necessity for mm or cm tick marks depends on the object being measured; the same holds true for ADC resolution.

Sensors (Transducers)

Sensors, also known as Transducers, translate physical phenomena such as temperature, force, and motion into voltage or current signals that can be utilized as ADC inputs. Examples of common sensors include thermocouples, thermistors, and RTDs for measuring temperature, accelerometers for measuring motion, and strain gauges for measuring force. When selecting a sensor for a measurement system, it is essential to evaluate its accuracy and the signal conditioning necessary to record a readable signal.

Signal Conditioning

Frequently, additional circuitry is required between the transducer and the ADC to perform accurate measurements on transducers. This circuitry can contain amplification/attenuation, filtering, Wheatstone bridge completion, excitation, linearization, calibration, and cold-junction compensation (CJC). Different sensors have varying requirements for signal conditioning. For example, strain gauge signal conditioning requires stimulation, bridge completion, and calibration. Before entering the ADC, thermocouples with output signals in the mV range must be amplified and filtered. Typically, signal conditioning circuitry is within a data-gathering device; however, signal conditioning may also exist within the transducer. For instance, load cells comprise bridge completion, calibration circuitry, and amplification. Numerous MEM (microelectromechanical) sensors include signal conditioning.


Data Loggers

Data Logging is the recording of gathered information over time. Depending on the application, the data may consist of temperature readings, voltages, currents, humidity, or other signals of interest. A Data Logger is a self-contained data collecting system with an integrated CPU and predefined software. Popular because they are portable and simple to use for specific purposes, data loggers can function as stand-alone devices.

Data Acquisition Devices

A data acquisition device (USB, Ethernet, PCI, etc.) has signal conditioning and an analog-to-digital converter but cannot work without being connected to a computer. They are a popular option since they are highly adaptable and may be utilized for various purposes.

Data Acquisition Systems

Modular data collection systems are intended for high-channel-count, complicated systems requiring the integration and synchronization of numerous sensor types. These systems are more challenging to integrate and operate, but they are highly adaptable.

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