Nollfrekvensen

Nollfrekvensen is a Swedish term that translates literally to “the zero frequency” and is used in physics, engineering, and signal processing to describe the frequency component of a system that corresponds to a constant or non‑oscillatory term. In the context of electrical circuits and electromagnetic fields it refers to the direct current (DC) component, whereas in mechanical and acoustic applications it can denote the static or quasi‑static influence of a force or vibration that does not change with time.

In Fourier analysis the nollfrekvensen is represented by the zero‑frequency coefficient in a Fourier series or transform. This coefficient gives the average value of the function over one period and is often called the mean or offset value. Removing or altering the nollfrekvensen is a common step in signal conditioning, for example when a bias voltage is subtracted from a sensor output or when a high‑pass filter is used to eliminate DC drift in a measurement signal.

In instrumentation, the concept of nollfrekvensen is employed to specify the effect of temperature changes or aging on equipment. A device’s zero‑frequency response can indicate how much its output changes in the absence of an oscillating input, thereby affecting calibration and long‑term stability. For example, a piezoelectric sensor that exhibits a non‑zero nollfrekvensen will produce a slowly varying baseline that must be compensated when converting the output to a physical quantity such as pressure or acceleration.

Because the nollfrekvensen represents a steady or slowly varying part of a system’s behavior, it is essential in both theoretical models and practical applications. It provides a reference against which dynamic components are measured, and it often serves as a point of calibration for instruments that must maintain accuracy over wide frequency ranges.