Noise

Signal noise in an industrial environment has the ability to cause havoc with process control systems. This electrical noise can inject itself into analog or digital signals and fool control equipment into thinking the process variable is different from what it actually is. This miscommunication between process control equipment, as with all kinds of miscommunication, can lead to any number of unforeseen, unintended consequences.

Signal noise, in its most basic sense, is any unwanted interference that degrades a communication signal. Signal noise can interfere with both analog and digital signals; however, the amount of noise necessary to affect a digital signal is much higher. This is because digital signals communicate using a set of discrete electrical pulses to convey digital “bits.”

Conversely, analog signals represent an infinite range of possible values using an established range, such as 4-20 mA or 0-10 V. In this case, any unwanted voltage or current spikes will cause a fluctuation in the message being communicated. Minuscule variations along analog signals, on the order of millivolts or microamps, typically do not result in a significant (or even perceptible) discrepancy. High levels of electrical noise, however, can produce large variations and therefore lead to substantial discrepancies making communication between process control devices utterly impossible.