Fundamentals of Test Measurement Instrumentation

The data acquisition or display section of a measurement system includes the equipment that connects to the output of the signal conditioning equipment and processes that signal into a form that the system operator can use. The equipment can be as simple as a digital meter or as complex as a computer-based data acquisition system. Which type is chosen depends on such factors as the number of signals to be accessed, how fast the data is changing, whether the data needs to be stored, and whether the data needs to be processed further.
A measurement system may contain several different types of displays depending on the operator's needs. For a given test, the operator may need to monitor the pressure, temperature, and flow of a fluid in a test rig. At the same time, the operator may need to store vibration measurements and perform online analysis of the vibration data. The monitoring could be done using digital indicators or a data acquisition system, while the vibration measurements could be carried out using a separate vibration analysis data acquisition system.
Digital voltmeters are the simplest type of digital indicator. These units measure the signal conditioner's DC voltage output signal and display the result in DC volts. A pressure transducer connected to a signal conditioner may provide a linear output of 0 to 10 volts DC when the input is changed from 0 to 100 psig. The signal conditioner output is connected to a digital voltmeter that has a...