TIPOS DE SISTEMAS DE ADQUISION DE DATOS (EN INGLES)

Data Acquisition Systems and Terms

Data acquisition systems gather information by measuring specific variables, then analyze the data and display the results in a designated format. Many data acquisition systems rely on computer systems to analyze data, but not all systems are necessarily complicated. Because data acquisition systems can measure a variety of different properties, such as temperature, voltage, and pressure, several devices can function as a primary data acquiring component in a data acquisition system. Transducers are often effective because they can measure a range of elements and translate and display the results in multiple forms. The kind of transducer used depends on the exact property being measured, and the display is also manipulated based on the user’s needs.

Once the appropriate transducer or other data acquisition device has been selected, it is important to determine if signal conditioning is needed. Sometimes, a transducer can pick up on a signal (voltage, for example) but the signal cannot be readily analyzed without first being translated into a different format. This is often the case when data acquisition hardware is in place. In order for a data system to analyze results, the output from the transducer must be either digital (discrete values) or analog (a continuous range of values).

For more information on the difference between analog and digital signals, visit Washington State University's page.


Before the signal can be processed by a computer, however, data acquisition hardware (DAQ) is often a necessary go-between for the signal and the PC. Generally speaking, DAQ consists of a small device that can be connected to a computer via a USB, parallel, or serial port, or can sometimes connect directly to the motherboard. The DAQ device includes its own applications, such as a multiplexer and several small programs. Some DAQ devices don’t need to be directly connected to the PC but can be operated independently.

However, DAQ hardware won’t be able to work with a PC unless it operates alongside DAQ software. Software can come in a variety of forms, including as an application built directly into the hardware component. Essentially, DAQ software enables a computer to understand the signals DAQ hardware is receiving and to run the appropriate programs. Each data acquisition system has distinct terms and devices associated with it. Some common terms that may further familiarize one with the components involved in various systems are listed and discussed below.

Analog-to-Digital Converter (ADC)
An analog-to-digital converter is commonly used in data acquisition systems to convert  analog signals into digital signals. Because many data acquisition systems can only read digital signals, this type of converter is extremely useful.

Digital-to-Analog Converter (D/A)
For data acquisition systems that can only understand analog signal input, a digital-to-analog converter can translate a digital signal into a comprehensible analog signal.

Digital Input/Output (DIO)
Data acquisition signals can have several states when they are in digital form: on/off, high/low, and 1/0 are all examples of DIO signal states, which are also called binary input/output (I/O) states because the signals are discrete. Analog signals, on the other hand, are continuous output signals rather than discrete values.

Differential Input
This term signifies the way a signal is designed for reception by a data acquisition system. Depending on the channel used to transmit the signal, differential input will either assume a high or low connection. Some data acquisition systems will either support differential input or a single-ended input (another way a signal is received by the system) although many systems can support both.

Single-Ended Input
Much like differential input, single-ended input is a manner in which a signal is wired for reception by a data acquisition device. Each signal has a high connection but does not each occupy an individual channel. Instead multiple signals share a connection.

Resolution
Resolution is the smallest amount of a signal necessary for recognition by a data acquisition system. Bits, proportions, or percents can be used to represent resolution.
Sample Rate
Sample rate refers to how quickly a data acquisition system can gather information. In devices with multiple channels, the sample rate is usually related to the speed of the analog-to digital converter. To determine the rate of an individual channel, simply divide the speed of the analog-to-digital converter by the number of channels being used.