Instrumentation - Data Acquisition

Sensor signals have to be converted to data (digitized) before they can be processed and stored. This process is called data acquisition. For vibration data the best solution is to acquire a dynamic signal, the function of acceleration over time. This function can later be processed with several algorithms to yield valuable machine condition and diagnostic data. The data acquisition process assigns a number to every level of acceleration at equal time intervals. It takes place in a data acquisition device that contains a micro processor, an ADC (analog to digital converter), necessary filters, and other components. In addition, the data acquisition device has to have means for sending the data out for further processing and storage.

There are many decisions that have to be made about the data acquisition. Here are some of the questions that are typically asked about data acquisition:

How much data has to be collected?

What is the required sampling rate?

What is the proper ADC resolution?

How the signal has to be filtered?

From the practical standpoint these selections must be made behind the scene in software and not by the user. However, many data acquisition systems assume technically savvy users who know how to use these parameters. A more user friendly system should ask a different set of questions:

What is required frequency resolution?

What is required analysis bandwidth?

What is required dynamic resolution?

Answers to these questions help set up proper data acquisition parameters and they borderline with our next topic - Data Processing and Storage.