In the example above of the digital meter, the signal changed at one Volt per second (which is much slower than an electrocardiogram). To accurately display such a waveform, you can look at the fastest rate-of-change in the signal, expressed in Volts per second. An electrocardiogram, for example, must be reproduced with considerable precision because some of the important things a doctor looks for are small changes in the waveform. In some applications it is necessary to accurately represent an input waveform. If the temperature is read only once per minute, it may not accurately display the temperature of an oven that is heating rapidly. When collecting data for analysis this can be a big problem.įrom the above discussion, it is clear that you need to determine the sample rate of a data acquisition system with care, but how do you choose? For slowly changing signals, like temperature, the only consideration is to provide a new reading so that the data is reasonably up-to-date. When reading a digital meter this is usually not a problem. This is the equivalent of having only one digit of resolution (or 10% resolution), because the change from one sample to the next is a change of one digit in the most significant or left-most digit. If it updates only 10 times per second it will change one Volt at each sample. A digital meter with three digits can resolve a change of 10 millivolts. Consider an input signal that changes from 0 to 10 Volts in once second. It is easy to overlook the effect of the time digitizing, but it can be much more important than the amplitude digitizing. The data is digitized in amplitude and time. The displayed value only changes when the next reading is made, every 100 milliseconds.Īll modern data acquisition digitizes the data. Although the actual input value may change between readings, the meter does not change. It reads the value and displays it, perhaps ten times per second. The digital meter is updated at a constant rate. Where the analog meter always shows the current input value, the digital meter does not. Not only is the data digitized in amplitude, but it is also digitized in time. This is a digital representation of the data, with changes in discrete steps where any step smaller than the resolution of the data acquisition device cannot be represented. You may also read data on a digital meter that displays the data as numbers. The needle moves smoothly to any position. This is an analog representation of the data. For example, in the past you may have read data on a meter with a needle that moves back-and-forth. The most important concepts of data acquisition have to do with digitizing the data so a device with a processor can use it. Ultimately data analysis can only be as good as the input data, so acquisition is responsible for providing high-quality data. The components of data acquisition systems include appropriate sensors, filters, signal conditioning, data acquisition devices, and application software.
#Basic data acquisition system pdf Pc#
A PC or other device can be used to collect real-world information such as voltage, current, temperature, pressure, sound, chemical sensing, heart rate, and thousands of other parameters. Acquired data can be displayed, analyzed, and stored.
Learn more about our story here, and how we can work together.ĭata acquisition is the sampling of continuous real-world information to generate data that can be manipulated by a device, such as a computer. Company It started with innovation and engineering services.
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