ABSTRACT
The fundamental task of a data acquisition system is the measurement or generation of real-world physical signals. Before a physical signal can be measured by a computer-based system, a sensor or transducer is used to convert the physical signal into an electrical signal, such as voltage or current. Multifunction boards are commonly used to measure analog signals. This is done by the analog-to-digital converter, which converts the analog voltage level into a digital number that the computer can interpret. Instrumentation amplifiers typically provide a differential input and selectable gain by jumpers or software. The differential input rejects small common-mode voltages. The gain is often software programmable. Sampling rate determines how fast the analog signal is converted to a digital signal. When measuring ac signals, sample must be at least twice faster than the highest frequency of the input signal.
