A coaxial induction probe for measuring the charge, size and distance of a passing object

•A new induction probe consisting of two coaxial sensors is presented.•The probe can measure the charge, size and distance of a passing object.•The probe was simulated with COMSOL, and calibrated and tested with charged spheres.•Finally, tests with powder in a fluidized bed were made.•The method is statistical, but on average the calculated values are close to correct.

A coaxial induction probe for measuring the charge, size and distance of a passing object is presented. Two different current signals were induced as an object passed the probes. The signals were integrated and Gaussian curves were fitted to the data. According to simulations done with Comsol Multiphysics, the charge, size and distance could be calculated from the amplitudes and widths of the curves. The system was simulated, built and calibrated. It was tested in powder measurements in a fluidized bed device.