Data Acquisition Systems (DAQ)

Data acquisition (DAQ) is the systematic measurement and recording of electrical characteristics or physical metrics with one of these end goals:

• design verification
• electrical or thermal characterization
• monitoring of an electronic, manufacturing, or physical process
• control over the testing of a product

A data acquisition (DAQ) system consists of a collection of hardware and software for sampling physical parameters such as voltage, current, temperature, and strain with a sensor or transducer. The system enables engineers to condition and convert samples into digital data for capture, live monitoring, and analysis.

A data acquisition unit is typically used for three main purposes: characterizing products, monitoring processes or products, and controlling test processes.

A static DAQ generally takes a single measurement as it scans through each input channel. It takes a measurement or measurements (if it has multiple input channels) at a fixed sampling rate suitable for slow-changing measurements such as temperature or humidity. However, a dynamic DAQ takes multiple samples of measurements in a quick successive manner for each of its input channels to capture fast-changing signals such as vibration, acoustic, or structural stress signals.

A data logger captures and logs data based on the scan interval, and the data logging period. A data acquisition system can perform data logging efficiently with multiple input channel switch multiplexers, built-in signal conditioners, and control systems to help automate the capture of signals from sensors.

A dynamic DAQ can sample a single or multiple sensors’ dynamic signals at a high sampling rate using its built-in hardware signal digitizer. Hence, it can capture transient signals of voltage, current, vibration, or structural stress changes. A modern DAQ has a built-in fast Fourier transform (FFT) mathematic algorithm to transform a time-domain signal display into a frequency-domain signal display. An engineer can then analyze the dynamic signal in both the time and frequency domains.

It is very common to have a data acquisition (DAQ) system placed remotely from many of your areas of measurement interests. For example, you have several temperature probes inside a temperature chamber with cables extended out to your DAQ system outside the temperature chamber. Your DAQ system and the temperature chamber are inside a laboratory while you monitor the temperature chamber temperatures with your laptop remotely from an office outside the laboratory. A data acquisition software PC application is needed to enable you to monitor your temperature sensors inside the temperature chamber. A DAQ software can usually configure your sensor connections to your DAQ system, capture all your test data per your data log setting, and display your data graphically in trend charts and histograms.

A dynamic signal is usually captured as a transient signal of voltage, current, vibration, structural stresses, or a drop shock pulse.Dynamic signal analysis can be done in either time or frequency domain. In the time domain, you can observe the transient signal behavior, such as its signature variations, magnitude, and repetitiveness. You can also observe the signal’s behavior in the frequency domain, such as magnitude frequency response, harmonics, mechanical vibration signatures, and more.