Electrostatic Nonintrusive Method for Measuring the Electric Charge, Mass Flow Rate, and Velocity of Particulates in the Two-Phase Gas–Solid Pipe Flows—Its Only or as Many as 50 Years of Historical Evolution

There are a lot of different noncontact methods for measuring the electric charges carried on solid particles, the mass flow rate, concentration, volume loading, mean flow velocity, and other flow electrical and mechanical parameters in the two- and multiphase gas-solid flows as those in pneumatic conveyance, in the air, etc. One of the methods is that based on the phenomenon of electrostatic induction. The nonintrusive probes, sensors, detectors, and transducers of different shapes are used as the first parts of measuring systems built to measure the aforementioned quantities, which are strictly related to the flow of charged particles, without any disturbance to them. The method presented here employs a ring-shaped metal electrode called a probe. The flow itself produces the electrostatic flow noise that is induced on the inner surfaces of sensing devices in the form of charge or potential or both whose values are proportional to the quantities measured. The signals obtained at the output of the sensing devices are a source of information about the flow of particulates. The very first information about the method, its metrological description, and practical application to the charge measurement was published for the first time 50 years ago, and this is the reason why the author has decided to present the method´s evolution and historical development, along with its many different aspects over that period.