What Is a Static Electricity Sensor?
A static electricity sensor is a type of device that measures the amount of static electricity in an object to be measured, also called a surface potential measuring instrument.
It is a non-contact sensor that utilizes the phenomenon that an electric field with a strength proportional to the amount of charge is generated around a charged object.
Static electricity sensors can measure static electricity not only on metals, but also on all dielectric materials such as plastic, glass, and water. In addition to installed static electricity sensors, handheld static electricity sensors are also available to pinpoint the location to be measured.
Since static electricity sensors depend on the measurement distance, the displayed potential also changes when the measurement distance is changed. Therefore, for accurate measurements, it is recommended to fix the sensor at a set distance.
Uses of Static Electricity Sensors
Static electricity sensors are used in manufacturing lines in a variety of industries, including semiconductors, electrical equipment, automobiles, food, and pharmaceuticals.
When static electricity is generated in a production line, dust and other particles are attracted to and adhere to parts, posing the danger of dust adhering to and mixing with products, or parts repelling each other, causing problems that can lead to quality and yield problems.
For this reason, static electricity countermeasures are essential to prevent the generation of static electricity on the production line, and static electricity sensors are needed to accurately determine the amount of static electricity generated at various locations on the production line in order to implement static electricity countermeasures.
Principle of Static Electricity Sensors
Static electricity sensors generally consist of a sensor section containing a detection electrode and an amplifier section that converts the detected electric charge into a voltage signal.
When a charged object approaches the sensor, the sensor part receives an electric field from the object and generates an induced charge proportional to the strength of the electric field by electrostatic induction. In front of the sensing electrode is an oscillating electrode called a chopper, which periodically changes the electrostatic field strength.
At this time, the induced charge changes periodically as well, and an alternating current flows between the sensing electrode and ground. This current is impedance-converted in the amplifier section and extracted as an AC voltage signal to determine the charged potential of the object to be measured.
When using static electricity sensors, it is important to note that even if the amount of static electricity in the object to be measured is the same, if the electrostatic capacitance is different, the obtained charged voltage will change. For example, if the object to be measured is in contact with a metal, its capacitance will be higher than that of a single object, and the measured blackout potential will be converted to a lower value even if the amount of electrostatic charge remains constant.