A new type of current sensor is proposed which is made compact in a rugged form and operates in the temperature range up to 150 degrees Celsius. The operating principle of the sensor is based on inverse magnetostriction. The sensor consists of two ring-shaped magne- tostrictive ferrite cores, a ring-shaped piezoelectric disc sandwiched between them and a toroidally wound pickup coil. An alternating voltage applied to the piezoelectric disc vibrates the assembly, causing cyclical stress variations in the ferrite cores. Core magnetization by the field associated with a current conducted through the sensor's central hole is, through inverse magnetostriction, modulated at the vibration frequency. The resulting time varying flux induces an alternating voltage in the pickup coil. The phase of the voltage is inverted when the flowing direction of the current is inverted. Hence the current can be detected by using phase-sensitive-detection. Basic characteristics of the current sensor were examined. The hysteresis in the output and its dynamic range were improved by introducing multiple narrow gaps to the magnetostrictive ferrite cores.
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