Frequency Distribution
Measurement errors in electronic sensors are often characterized by the distribution of power across the frequency spectrum. The noise spectral density indicates how much noise power is present in a one hertz bandwidth. This metric allows engineers to predict the total noise of a system based on its operating frequency range.
It is expressed in units of volts or amps per square root hertz.
Power Measurement
White noise appears as a flat line on a spectral plot because it has equal energy at all frequencies. Sensors also exhibit flicker noise which increases at lower frequencies. The transition point between these two behaviors is known as the corner frequency.
Analyzing these patterns helps in selecting the right filtering strategy.
Bandwidth Integration
Total root mean square noise is calculated by integrating the density over the effective bandwidth of the circuit. A wider bandwidth lets in more noise and reduces the resolution of the measurement. High resolution systems use narrow digital filters to exclude unwanted frequencies.
This trade off between speed and precision is a fundamental design constraint.
Sensor Resolution
The smallest detectable change in a physical signal is limited by this internal noise floor. Manufacturers specify this value at reference conditions.
