Electrical field strength sensors are used to measure the strength of electrical fields. Electric fields are the product of voltage and become stronger as the voltage increases. DC electric field strength sensors are used to measure static charges. Sometimes electrostatic charges build up during the manufacturing, assembling, handling and other operations that are involved in making a product. In some instances the build up of electrical charge in delicate electronic circuits could seriously damage or even destroy them. The more sensitive the product is to electrical charge, the greater the need for using electric field strength sensors to prevent damage from happening.
AC electrical field strength sensors measure the strength of electrical field produced by alternating current. In alternating current, the direction of the field alternates from one polarity to the opposite and back again during each cycle. The number of cycles that occurs in one second is the frequency of the alternating current. In North America, electricity typically alternates through 60 cycles per second, or 60 Hz. In many other parts of the world, the frequency of electric power is 50 Hz. Many electrical field strength sensors can detect the frequency of the alternating current as well as the strength of the field.
EMF electric field strength sensors are sometimes considered a specialized type of electric field strength sensor, designed to detect the electric fields that are associated with electric power distribution and transmission lines.
Another type of electric field strength sensor is the atmospheric electric field sensor, sometime referred to as "field mills" because a rotating vane is employed in making the measurement. These electric field strength sensors are used to measure the atmospheric electric field as a means of assessing for lightening to occur in a give locale.