The Application of Thin Film Sensing Technology in Passive Optical DC Current Sensor

There are many technical difficulties in existing passive optical DC current sensor, so a DC current sensor based on optical fiber thermometry is proposed in this paper. The tested current generates applied voltage by a shunt and transfers into the change of temperature rising after a thin film resistor in the high voltage side. Then the current information is got indirectly by measuring the temperature signal. The new project combines the thin film sensing technology and the temperature measurement technology. It does not have polarized light, fragile optical glass block and the power supply in high voltage side, so it does not exist the difficulties of the main project at present. As the thin film resistor is a key device, dynamic characteristic of which is analyzed. Mathematic model and three-dimensional ANSYS simulative model of thin film resistance is built. Thermal analysis is performed according to their shape, material, structure, process and size. An experimental thin film resistor is constructed for testing. Theoretical analysis and experimental results show that this scheme is available if appropriate technique are used.