Short Answer:

Electrical noise in measurement systems refers to unwanted signals or disturbances that interfere with the actual data being measured. These noises can come from various sources such as electromagnetic interference (EMI), power lines, radio signals, ground loops, switching devices, or even from within the electronic components themselves.

Such noise can affect the accuracy and reliability of measurements by creating false signals or distortion. Understanding these noise sources is important for designing clean, stable, and accurate electrical measurement systems, especially in sensitive or high-precision applications.

Detailed Explanation:

Sources of electrical noise in measurement systems

In any electrical measurement system, achieving accurate and stable results is a key goal. However, electrical noise can interfere with signals and cause errors, false readings, or degraded performance. Noise is any unwanted electrical signal that mixes with the desired signal and reduces the system’s ability to detect or process correct information.

There are various types of noise, and they originate from both internal and external sources. Understanding these sources is essential for minimizing their effects through proper shielding, grounding, filtering, and circuit design.

Common Sources of Electrical Noise:

1. Electromagnetic Interference (EMI):
   EMI is caused by electromagnetic fields from nearby electronic devices such as motors, transformers, relays, and communication equipment. These fields induce unwanted voltages in sensitive circuits.
   • Example: A motor running near a sensor cable can inject noise into the signal wire, affecting the sensor’s output.
2. Radio Frequency Interference (RFI):
   RFI is a high-frequency form of EMI that comes from radio transmitters, mobile phones, Wi-Fi routers, and other wireless devices.
   • These signals may couple into measurement cables and circuits, especially when shielded cables are not used.
3. Power Line Interference (50/60 Hz):
   The AC mains supply (typically 50 Hz or 60 Hz) is a common source of noise. Any nearby unshielded wiring can induce this frequency into signal lines, especially in low-voltage or analog systems.
   • Fluorescent lights, power supplies, and AC fans can also contribute to this type of noise.
4. Ground Loops:
   Ground loops occur when there are multiple ground paths with different potentials. This creates circulating currents that cause voltage differences, adding noise into the measurement system.
   • Common in systems with poorly planned grounding or long cable runs.
5. Switching Devices and Digital Circuits:
   Switching power supplies, digital logic circuits, and microcontrollers produce high-speed transitions (on-off pulses), which generate noise. These can couple into analog lines through electromagnetic radiation or shared ground paths.
   • Especially problematic in mixed-signal systems (analog and digital together).
6. Thermal Noise (Johnson Noise):
   This is caused by the random motion of electrons in resistors and other passive components due to temperature. It is unavoidable but usually very small.
   • Significant in low-signal or precision systems where every microvolt matters.
7. Shot Noise and Flicker Noise:
   These are internal noise sources generated by electronic components like transistors and diodes due to current flow variations.
   • Typically observed in amplifiers or sensor circuits.
8. Capacitive and Inductive Coupling:
   Noise can be transferred from one wire to another through capacitance (electric field) or inductance (magnetic field), especially when signal and noise wires run parallel without shielding.
9. Environmental Sources:
   Static electricity, lightning, or even human movement near highly sensitive systems can generate noise pulses or transients.

Conclusion:

Electrical noise in measurement systems can arise from external sources like EMI, power lines, and switching devices, or from internal sources such as resistive and transistor noise. These disturbances interfere with signal accuracy and must be minimized through good circuit design, proper shielding, grounding, and filtering. Identifying and controlling noise sources is essential for building reliable and precise measurement systems.