Remote controlled signal conditioner and fiber optic data link system development for CPRF

The ZTH reversed-field pinch to be installed in the Confinement Physics Research Facility, (CPRF) will produce a significant ambient magnetic field. To avoid ground-loop and other electrical problems, the diagnostics in direct or possible contact with the experiment will be accessed through a fiber-optic data way. The frequency-modulated analog links developed for this system have a bandwidth of DC to 100 kHz and a signal-to-noise ratio of better than 60 dB. The fiber-optic transmitter units include a signal conditioner and a microprocessor controller. The conditioners can be configured as DC coupled, low-noise differential amplifiers, or as high-gain, low-drift differential integrators with a very long droop time constant. Magnetic-field pickup is minimized by balancing sensitive circuit areas to within 5 mm² in all three planes of the PC boards. The gain, offset, and integrator reset are controlled and monitored by the microprocessor, and their status is displayed on the front panel of the transmitter unit. The signal conditioner can be controlled locally, or by way of a fiber-optic coupled control network. The system allows fast, convenient, noise-immune control of a large number of signal conditioners from a central host computer. By varying the offset, the computer can verify the operational integrity of the data links