Gigaohm

A gigaohm, symbolized as GΩ, is the SI unit of electrical resistance equal to one billion ohms (10^9 Ω). It is used to express very high resistances found in insulation and other high-impedance contexts.

In practice, gigaohms describe insulation resistance between conductors separated by dielectric material, such as cables, electrical insulators, and transformers. The extremely large resistance means correspondingly small leakage currents; for example, at 1 V across 1 GΩ, the current would be about 1 nanoamp, and at 1000 V it would be about 1 microamp. This makes GΩ measurements important for assessing the integrity of insulation and the stability of high-impedance circuits.

Measurement techniques and considerations: insulation resistance testers (often called megohm meters) and electrometers are used to measure in the GΩ range. Readings can be influenced by environmental factors such as temperature and humidity, surface leakage, polarization effects in some dielectrics, and electrode geometry. Measurements typically involve applying DC voltages and allowing time for stabilization, with care taken to account for leakage paths and measurement polarization that can distort results.

Applications: gigaohm-scale resistances are common in the assessment of insulation in power systems, including cables, transformers, and switchgear, as well as in research on dielectric materials and high-impedance sensors. High-resistance values in the GΩ range are also encountered in materials science studies of pristine insulators, clean surfaces, and certain semiconductor or detector components.