Abstract: An ultrasonic transducer for measuring a property of a material within a defined space has a function of a velocity at which ultrasonic signals travel through the defined space includes a controller. The controller is adapted for coupling to a plurality of ultrasonic transducers. The controller include a multiplexer for selecting one of the plurality of ultrasonic transducers, signal processing means for processing an output of the selected ultrasonic transducer and controller means for providing parameters to the signal processing means based upon the selected ultrasonic transducer. The controller couples to a two wire 4-20 mA communication loop. The controller periodically excites the ultrasonic transducer to obtain a measurement. The controller stores power received from the two wire communication loop and excites the transducer using stored power. The controller is capable of providing power which exceeds that available directly from the two wire communication loop for a brief period of time.

Abstract: Patient bed alarm system (10) is the subject of the present invention. The system (10) includes a plurality of sensors defining interstices (18) of a matrix (16) of such sensors. The matrix (16) is woven into a mat (14) for placement on a bed (12) in which a patient is confined. The presence of the patient's body upon the mat (14) causes various combinations of the sensors to perceive the presence of the patient's body thereon. The particular combinations of sensors sensing the presence of the body is inputted to a first micro computer (20) which discriminates as to the exact location of the patient in view of the exact combination of sensors perceiving the presence of the patient's body. If the combination of sensors actuated indicate an impending vacation of the bed (12) by the patient, an alarm (26, 28) can be actuated by a second micro computer (24) to alert monitoring personnel of the situation.