4 Ways Signal Noise Can Impact Electrical Equipment

• Electromagnetic Noise: As previously mentioned, this type of noise is generated by external electromagnetic fields that affect the surrounding circuitry. Sources can include radio transmitters, power lines, and household appliances.
• Radio Frequency Interference (RFI): RFI is a subset of EMI specifically caused by radio frequency signals. It is commonly caused by wireless communication devices, microwaves, and other radio wave-emitting electronics.
• Power Line Noise: This is most commonly generated by the fluctuation in the power supply, such as voltage spikes, surges, and transients. It can be caused by a myriad of reasons, such as faults in the power distribution network.
• Crosstalk: Crosstalk happens when a signal from one circuit or channel creates an undesired effect on another, which is common in densely packed electronics and poorly designed audio systems that might require additional insulation or shielding.
• Thermal Noise: Known as Johnson-Nyquist noise, thermal noise is generated by a chaotic motion of electrons caused by the heat generated by the passing of electricity. Unfortunately, it is inherent in all electronic devices, but it’s most common at higher frequencies.

Certain types of signals and their different levels are typically negligible, as they’re often considered just a nuisance. However, in high-fidelity and high-sensitivity applications, such as precise measurements or HI-FI audio, electrical noise has a variety of detrimental effects on signal quality and electrical equipment. Understanding these impacts is important for mitigating them.

The degradation of signal quality is a direct and immediate result of signal noise, which can result in data errors (due to the corruption of transmitted data). In digital systems, the noise causes bit errors, which leads to incorrect data interpretation and processing. In analog systems, however, the noise distorts signal wavelengths, making accurate signal reproduction impossible. In either case, data errors are a major issue for precise data transmission, especially in control systems.

As stated above, signal noise interferes with control signals, which is really detrimental in industrial automation since it affects the signals between sensors, actuators, and controllers, leading to faulty operation and false readings.

Signal noise can cause unpredictable behavior in electrical components, which can lead to potential failures. For example, noise-induced glitches in CPUs and processors can cause crashes. In power systems, signal noise can also trigger protective relays, which can lead to unexpected and unnecessary shutdowns.

Since it can adversely affect signal quality, impact signal control, and lead to equipment malfunction, signal noise has the potential to affect product quality, especially in precision manufacturing. It can interfere with CNC machine operations, the functioning of robotic arms, and other automated equipment, leading to the appearance of defects in the final product.

Manufacturing aside, signal noise is also a problem in quality assurance, as electrical noise can corrupt the data collected by sensors and inspection devices. This can result in inaccurate measurements and faulty quality assessments, causing increased scrap rates, rework, and customer dissatisfaction, ultimately affecting the profitability of a business.

Shielding refers to enclosing sensitive equipment in conductive materials that have the potential to block external electromagnetic interference and thus eliminate noise. It also applies to conductors and cables, which usually have a copper braid or an aluminum strip that’s woven around the cable between the inner and the outer insulation layers. Shielding is usually connected to the ground, which drains the unwanted signals away.

Grounding, especially in terms of shielding, provides equal and constant reference points for electrical systems while also providing a path for electrical noise to dissipate safely. It actually “pulls” the noise away. Proper grounding methods include single-point grounding and grounding of cable shields.

Filtering involves using powerline filters, such as capacitors and inductors, to remove any unwanted noise from power lines or signal paths. This is mostly achieved by smoothing out voltage fluctuations in power applications or by using low pass, high pass or band pass signal filters for signal conditioning applications.

Using twisted pairs and shielded cables helps reduce crosstalk and external noise. Twisted wires equalize the signal noise between both wires, canceling the signal noise. Additionally, by layering the cable with additional shielding, the cable is protected against external EMI.

Maintaining physical distance between power and signal cables can prevent power line noise from coupling into signal lines. This is usually achieved by routing cables separately and using different line paths for power and signal cables.

Differential signaling relies on two complementary signals to transmit data. It’s a digital equivalent of a twisted pair; both signals are equally affected by noise, but the difference between the two signals remains the same. Thus, the impact of signal noise on electrical equipment is kept to a minimum.

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