Abstract: Embodiments of the present invention are directed to method and devices for measuring the pressure of a pump chamber in which no internal opening or connections are needed. One embodiment of the present invention is directed to an apparatus for pumping fluid. The apparatus comprises at least one housing having a transducer surface. The transducer surface has a thickness exhibiting measurable deformation upon the chamber holding a fluid under pressure such that the transducer surface has a first position at which the chamber is at one pressure and a second position at which the chamber is at a second pressure. A strain sensor is affixed to the transducer surface producing; at least one signal upon the transducer surface assuming the first position and at least one signal upon the transducer surface assuming the second position to function as an integrated pressure transducer.

Abstract: Embodiments of the present invention are directed to method and devices for measuring the pressure of a pump chamber in which no internal opening or connections are needed. One embodiment of the present invention is directed to an apparatus for pumping fluid. The apparatus comprises at least one housing having a transducer surface. The transducer surface has a thickness exhibiting measurable deformation upon the chamber holding a fluid under pressure such that the transducer surface has a first position at which the chamber is at one pressure and a second position at which the chamber is at a second pressure. A strain sensor is affixed to the transducer surface producing; at least one signal upon the transducer surface assuming the first position and at least one signal upon the transducer surface assuming the second position to function as an integrated pressure transducer.

Abstract: An electronic control system for sequential actuation of a four-way solenoid valve is used to selectively load and unload a slide valve control for a screw compressor. The electronic control system can be responsive to output or refrigerant pressure or evaporator pressure or inlet pressure and pulses a four-way solenoid valve to selectively load and unload the compressor so that it will maintain system pressure within a preselected deadband. Selective pulsing of the four-way solenoid valve is used to gate hydraulic fluid to load and unload chambers separated by a piston coupled to a slide valve which shifts longitudinally and changes the capacity of the screw compressor. The control system senses system pressure (reflecting load), and when a limit pressure is reached, a gas bypass solenoid valve (or dump valve) and fast-unload system is actuated to entirely unload the compressor. The control circuit also monitors current to the motor which drives the screw compressor.

Abstract: An electronic control system for sequential actuation of a four-way solenoid valve is used to selectively load and unload a slide valve control for a screw compressor. The electronic control system is responsive to output air pressure and pulses a four-way solenoid valve to selectively load and unload the system so that it will maintain system pressure within a preselected deadband. Selective pulsing of the four-way solenoid valve is used to gate hydraulic fluid to load and unload chambers separated by a piston coupled to a slide valve which shifts longitudinally and changes the capacity of the screw compressor. The control system senses output line pressure, and when a limit pressure is exceeded, a dump solenoid valve and fast-unload system is actuated to entirely unload the system of air pressure until reduced to a level below the set deadband. The control circuit also monitors current to the motor which drives the screw compressor.

Abstract: A voltage to frequency converter includes an input signal integrator, a level detector connected to the output of the integrator, clock-signal-controlled logic illustratively comprising a D-type clocked flip-flop circuit connected to the output of the level detector, and a reference signal switch which applies a positive or negative reference signal to the integrator depending upon the logic level of the output of the logic. The polarity of the reference signal applied to the integrator is continuously switched causing the output of the integrator to move alternately in a positive and negative direction. Positive integration cycles are thus continuously opposed by negative integration cycles. The clock controlled logic forces each integration cycle to be an integral multiple of a clock signal pulse length in duration. The output of the logic is a pulsed signal 1aving a pulse rate or frequency proportional to the input signal voltage.