Miniaturized current transformers for multirange operation of milliammeter ink recorders

Conventional forms of multi-range current transformers with a rated output of 5 or 10 va (volt-amperes) cannot be employed for operation of standard moving-coil milliammeter ink recorders which require about 1.5 mw (milliwatts) for full-scale deflection. Recently developed a-c and d-c types of miniaturized current transformers using cores of thin molybdenum-permalloy tape and special construction (extremely small cross-sectional area of the core and very large number of turns of the secondary winding) make multirange operation of such recorders possible.