Noise Reduction and Isolation

Fig. 10.01. Utility power transformers are typically grounded to earth ground near the transformer, and again at the input to the electrical junction box or first switching panel. The switching panel, in turn, may be connected to a rod driven into the earth to ensure that it too is at true ground potential. Control Panel Grounding CONTROLLING NOISE Controlling noise in measurement systems is vital because it can become a serious problem even in the best instruments and data acquisition hardware. Most laboratories and industrial environments contain abundant electrical-noise sources, including AC power lines, heavy machinery, radio and TV stations, and a variety of electronic equipment. Radio stations generate high-frequency noise, while computers and other electronic equipment generate noise in all frequency ranges. Building a completely noisefree environment just for running tests and measurements is seldom a practical solution. Fortunately, simple devices and techniques such as using proper grounding methods, shielded and twisted wires, signal averaging methods, filters, and differential input voltage amplifiers can control the noise in most measurements. Some techniques prevent noise from entering the system, while others remove extraneous noise from the signal.