Ultra Low-Cost High-Voltage Isolated Differential Probe for Teaching and Training

Measurement of time-varying high-voltages is necessary in various teaching, training, and research scenarios, in domains ranging spanning multiple disciplines beyond just electric power engineering. While low voltage levels (<100V) can usually be measured directly by oscilloscopes with inexpensive passive probes, higher voltages (>400V) often require specialized probes and/or oscilloscopes which are expensive. Also, most oscilloscopes lack galvanically isolated channels, which adds further challenges to measurement of multiple floating (not grounded) high voltages. Although both problems can be solved by differential high-voltage probes, these are quite expensive and not cost-effective for teaching laboratories where large numbers of such probes may be needed. This paper presents a novel, inexpensive isolated high-voltage differential probe intended for use in undergraduate and graduate labs in Power Electronics, Electric Machines and Drives, Renewable Energy, etc. It is designed for input voltages up to 600V with a bandwidth of 350KHz. The design is self-contained with a removable lithium-ion battery and is designed to directly interface to a standard oscilloscope. The design also includes gain and offset correction for periodic calibration. Simulation results were validated using a preliminary hardware prototype, following which a compact version was created with optimized layout. This design is found to be excellent for cost-sensitive applications including universities, makerspaces, and startups and industries.