Abstract: A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. In one embodiment, the pressure sensors comprise variable capacitors.

Abstract: A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. In one embodiment, the pressure sensors comprise variable capacitors.

Abstract: A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. In one embodiment, the pressure sensors comprise variable capacitors.

Abstract: A monolithic temperature and pressure transducer having a plurality of capacitive sensors. The capacitors are formed from the same silicon substrate and are equally affected by temperature variations, including temperature gradients.

Abstract: Integrated transmitters and controllers for use in monitoring process variables. A transmitter and controller for monitoring and controlling a process variable in a process control loop comprises a transmitter for producing a digital signal indicative of the process variable's state, and a digital controller supplied with the digital signal from the transmitter responsive to the digital signal, and further interfaced in a process control loop for controlling the process variable in response to the digitally communicated signal from the transmitter. Integrated transmitters and controllers described herein simplify installation and maintenance of industrial process control systems and place the controller functions at the process variable, thereby increasing control system efficiency.

Abstract: A thermal drop-on-demand ink jet print head in which a heat delay means is provided covering a predetermined part of the resistive element. Upon connection of an electrical signal to energize the resistive element, nucleation occurs at an uncovered location on the resistive element and formation of the bubble proceeds in a direction toward the covered part of the resistive element to thereby utilize the inertial effect of the controlled bubble motion to eject a drop of ink in a more energy-efficient manner.

Abstract: An acoustic flow meter in which a plurality of different frequencies are transmitted in both upstream and downstream directions, and corresponding differences in transmission phase-delays due to such frequency changes detected and used to compute the fluid velocity by the formula ##EQU1## when L is the distance between transmitter and receiver, M.sub.D is the slope of the graph of phase delay vs. transmitted frequency for the upstream direction of transmission, and M.sub.u is the corresponding slope for the downstream direction. A signal processor using a least-squares algorithm is preferably employed to obtain best values for M.sub.D and M.sub.u from the several values of phase-delay difference produced by the several different transmitted frequencies.

Abstract: A calibrating device is disclosed for insertion between a control station and its indicators, preferably of the bar graph type, with provisions for establishing accurate reference voltages available at marked jacks for use and specifically for checking the calibration of the indicating elements, and to provide for utilization of one or both indicators as a precision voltmeter for checking the potential of various points in the circuitry. Provisions are also made for bypass plugging in so that the indicators operate in a normal manner as if the calibrator were not present. The normal jacks also provide convenient access to the set-point and variable voltage of the station and facilitate the measuring of these voltages by an external digital voltmeter if desired.

Abstract: A control circuit for bar graph display panels is described which reduces the tendency to drift, which obviates the necessity of maintaining an absolutely constant oscillator frequency and an absolutely constant ramp rate by utilizing a feedback system to reference the ramp end points to a single precise voltage.

Abstract: A pressure to electric transducer is described employing an electrical capacitance formed by two parallel metal plates separated by a variable air gap, one of the plates being fixedly mounted and the other being movable to change the spacing in direct proportion to fluid pressure acting on an input element or capsule to which the movable plate is connected. The capacitance forms one leg of a negative feed back divider network, for controlling an operational amplifier so that its gain is directly proportional to the spacing of the plates. The amplifier is driven by a constant alternating current source so that its output is directly proportional to the applied pressure. The voltage output can be rectified and transformed in a conventional manner for transmission of a signal.