Fisher
2500 249 Series Pneumatic Controllers and Transmitters
Typical caged and cageless sensor/ instrument configurations are shown in figures 1 and 2. Caged sensors ( figure 3) provide more stable operation than do cageless sensors ( figure 4) for vessels with internal obstructions or considerable internal turbulence. Cageless sensors are generally used on specific gravity and interface control applications requiring large displacers that are more easily accommodated by flange connections up to NPS 8. The availability of many different displacer stem lengths permits lowering the displacer down to the
most advantageous depth in the vessel. Fisher pneumatic controllers and transmitters are
used wherever rugged, dependable, and simply constructed displacer style pneumatic instrumentation is required in liquid level, interface level, or density service. The ruggedness of these products is demonstrated by their use in many kinds of demanding applications, including those in the power, chemical process, oil and gas production, and petrochemical industries.