Abstract

An indicating and control apparatus uses Hall effect elements arranged on one side of a non-magnetic wall separating the elements from selectively positionable respective magnets. The magnets are selectively positioned adjacent to the non-magnetic wall to energize respective ones of the Hall effect elements by a code disc which is selectively positionable and displaceable with respect to the wall. The code disc is attached to a manually rotatable knob projecting from a housing enclosing the selectively positionable magnets and having a dial face on the exterior surface of the housing to cooperate with an indicator on the knob. The Hall effect elements, in turn, are located on a printed circuit board and are connected to associated circuitry to bias the Hall effect elements and to utilize output signals from the Hall effect elements. In a specific embodiment the printed circuit board is associated with a pressure sensor which is arranged to supply electrical signals representative of respective fluid pressures to signal storage elements on the printed circuit board in combination with the output signals from the Hall effect elements for utilization as data and control signals, respectively, by a data processing system connected to the indicating and control apparatus.