Precision fiber-optic current sensor as a check-standard

A DC-coupled fiber-optic current sensor with check-standard performance is discussed. The high-energy output of the fiber-optic sensor has a linearity of 0.01% from 10 to 3600 A/sub rms/. The low energy output has a linearity of 0.04% from 200 to 4500 A/sub rms/. For these outputs, the scale-factor-error temperature performances are 0.02% for the low energy output and 0.04% for the high-energy output. The temperature range used is 5 to 40/spl deg/C for both the electronics and the optical sensing head. The phase error temperature performance is nearly 0.1 min in a laboratory environment. Also, a 1 ppm optical flux nulling current sensor is employed to make low uncertainty measurements on the high-energy output of the current sensor.