Ohmimittaus

Ohmimittaus is the process of measuring electrical resistance, expressed in ohms (Ω). It is used across electronics, metrology, and materials science to characterize components, conductors, and devices, and to diagnose faults.

There are several measurement methods. The simplest is a two-point method using a handheld multimeter, which can be fast but includes the resistance of leads and contacts. A four-point (Kelvin) method uses separate current and voltage probes to cancel lead and contact resistances, yielding more accurate results for low resistances. Impedance analyzers and LCR meters measure resistance as part of complex impedance across AC frequencies, useful for resistive, inductive, and capacitive components. For very precise work, bridge methods such as a Wheatstone bridge or specialized low-resistance measurement systems are employed. In materials science, four-point probe and van der Pauw methods are used to determine sheet resistance and resistivity.

Temperature and frequency influence ohmimittaus. Resistance changes with temperature according to a material's temperature coefficient, and measurements are typically reported at a reference temperature (commonly 20–25°C). DC resistance is real-valued, but at higher frequencies measured impedance includes reactive components, so care is needed to distinguish pure resistance from reactance.

Good practice includes ensuring clean, secure connections, using Kelvin probes when precision is required, calibrating instruments against known standards, and reporting measurement conditions such as temperature, frequency, and method. Ohmimittaus supports quality control, device characterization, and research in electronics and materials.