Abstract: A method and apparatus are disclosed for deriving digital signals from analog variations of different sensing elements in a transducer. Each sensing device controls the frequency of a variable frequency oscillator, which is energized when a reading is to be taken for that specific sensing device. The periodic signal is coupled to a first counter which counts a presettable total number of cycles so as to establish a variable time period proportioned to the value represented by the then existing state of the sensing device. Concurrently, a second counter is operated for a like time interval, but counts cycles from a fixed frequency clock source at a much higher frequency. The number of cycles counted by the second counter is proportional to the analog signal from the sensing device. This arrangement enables the analog signals from the sensing devices to be digitized in sequence with compact circuitry having low power drain.

Abstract: A method and apparatus are disclosed for deriving digital signals from analog variations of different sensing elements in a transducer. Each sensing device controls the frequency of a variable frequency oscillator, which is energized when a reading is to be taken for that specific sensing device. The periodic signal is coupled to a first counter which counts a presettable total number of cycles so as to establish a variable time period proportioned to the value represented by the then existing state of the sensing device. Concurrently, a second counter is operated for a like time interval, but counts cycles from a fixed frequency clock source at a much higher frequency. The number of cycles counted by the second counter is proportional to the analog signal from the sensing device. This arrangement enables the analog signals from the sensing devices to be digitized in sequence with compact circuitry having low power drain.

Abstract: In a differential pressure transducer having isolation diaphragms on opposite sides of a sensing diaphragm, the isolation diaphragms are made highly compliant, are radially prestressed and are bowed outwardly relative to closely spaced backup surfaces by oil pressure. Using very small interior cavities and a substantially stiffer sensing diaphragm differential process pressures induce linear deflection of the sensing diaphragm.