Elektrometer

An electrometer, or elektrometer, is a high-sensitivity instrument used to measure electrical charge, electrical potential, or very small currents. It is designed to minimize the disturbance of the system under test by presenting a very large input impedance, allowing the detection of tiny charges and minute currents.

Principles of operation vary, but common approaches rely on isolating the input with a high-impedance element so that small charges can produce measurable effects. Some electrometers detect charge via electrostatic deflection of a movable electrode or changes in capacitance; others convert charge to a voltage with a high-gain amplifier. Vacuum-tube electrometers and electrostatic voltmeters rely on electrostatic forces, while modern devices often use solid-state electronics, including operational amplifiers with very low input leakage, to achieve high sensitivity and stable readouts.

Types of electrometers include vacuum-tube electrometer tubes, which provide extremely high input impedance for applications such as radiation dosimetry and fundamental measurements; electrostatic voltmeters that measure potential differences; and solid-state electrometers that integrate high-input-impedance front ends with precise current, charge, or voltage readouts. Some instruments emphasize direct current measurement, while others are designed to monitor accumulating charge over time.

Applications span physics research, metrology, radiation dosimetry, semiconductor testing, surface science, and mass spectrometry, where measuring charge, voltage, or current with minimal disturbance is essential. History traces electrometers from early electrostatic devices in the 19th century to Kelvin’s developments and onward through vacuum-tube and modern solid-state variants, reflecting ongoing improvements in sensitivity and stability.