Abstract: An electronic, programmable device for controlling the motion of compressor valve elements, wherein the device receives an incoming signal from a velocity sensor located on a compressor valve; filters, amplifies, and processes the incoming signal by a control algorithm; and responds to the incoming signal by creating an output signal that produces an actuator force that is applied directly to a moving valve element and associated methodology.

Abstract: An electronic, programmable device for controlling the motion of compressor valve elements, wherein the device receives an incoming signal from a velocity sensor located on a compressor valve; filters, amplifies, and processes the incoming signal by a control algorithm; and responds to the incoming signal by creating an output signal that produces an actuator force that is applied directly to a moving valve element and associated methodology.

Abstract: An improved biological signal detector which is extremely sensitive, yet resistant to the effects of high frequency noise. A multiplexed signal representation of a plurality biological signals is demultiplexed by a detector circuit comprising a plurality of switches each of which controls an individual storage network. A switch logic control circuit synchronizes the various switches to close during the time intervals corresponding to the pulse amplitudes representing the particular signal of interest. The amplitude of the alternating component of each of the biological signals is stored in one of the respective storage networks over a number of pulse time intervals. In the preferred embodiment, the storage networks of the detector each have a time constant which is purposely chosen to be substantially longer than the time interval of the pulses.

Abstract: A cardiovascular monitor having improved safety features and data transmission ability. Sensing devices placed on a patient's body, such as electrocardiogram electrodes and phonocardiogram microphones, are electrically isolated from the data recorder and AC powerline, thereby protecting the patient from dangerously high voltages existing in the recorder and the external power source. Isolation amplifiers are employed in the signal conditioning circuitry at the front end of the recorder. Special isolation transformers are also used to prevent ground loop currents between the signal conditioner and the recorder thus minimizing noise due to powerline leakage. Similarly, isolation amplifiers are used during the playback mode between the recorder and a data processor to avoid ground loop currents between the recorder and the processor.

Abstract: An interference resistant biomedical transducer for monitoring the acoustic output of a patient's cardiac or respiratory system which provides a high degree of rejection of acoustic noise and spurious electromagnetic signals. The transducer comprises a piezoelectric diaphragm assembly having electrodes which produce a differential output signal. The transducer housing includes a massive metal disc and a compliant handle which provide a mechanical filter to remove undesired signals such as those related to motion of the patient and ambient acoustic noise.

Abstract: A leak detection and location method and apparatus for detection of perforations in a obscure geomembrane liner is set forth. In a typical application, upper and lower liners are positioned contiguous to one another and a conducting liquid is placed between them. In the event a tear or perforation is formed in the lower liner, a current flow path is established from a power supply and conductors connected to the power supply. The current flow path extends through the liquid to the leak. Because of the liquid path through the liner, electric current will flow through the perforation and establish an associated magnetic field in the near vicinity of the leak. Magnetic sensors are then swept across the surface of or through the impounded liquid above the liners to indicate such magnetic field variations and the locations of such perturbations correspond to the locations of the leak perforations.

Abstract: A directional potential analyzer method and apparatus using a non-intrusive electrical measurement technique to obtain a precise location of a leak in a geomembrane liner. The method and apparatus can be used for detecting leaks in either a single layer or a two layer geomembrane liner. The directional potential analyzer comprises a differential voltage detection probe which is moved through the liquid with the potential difference between the electrodes on the probe being measured and recorded as a function of azimuthal position of the probe. An initial scan of the liquid impoundment is used as a reference trace showing all of the anomalies of an unfaulted liner. Subsequent traces obtained by rotating the analyzer probe at a later date are processed and compared with the reference trace to determine the occurrence of new anomalies representing leaks in the liner.

Abstract: An automated search apparatus is disclosed for detecting leaks in liquid impoundments usually defined by a geomembrane layer. A voltage gradient is created within the impoundment by means of a source electrode. The search apparatus contains pairs of electrodes coupled to differential amplifiers which allow plotting of the voltage gradient within the impoundment. The search vessel is controlled via radio telemetry, and its position may be tracked using optical theodolites. A distortion in the equipotential lines associated with the voltage gradient indicates the presence of a leak.

Abstract: A battery charger circuit having a temperature-dependent constant voltage region, a constant current region, and a power dissipation limiting current "foldback" region.

Abstract: A current limiting circuit for a switching regulator comprising a current sensing means operably connected to the positive terminal of a source of unregulated power and switching means operably connecting the positive terminal of said power source to the shut down input signal position of the switching regulator. When said current sensing means detects current in the positive terminal exceeding a predetermined value, the circuit of the present invention causes the switching regulator to adjust downward its duty cycle thereby preventing damage to the switching regulator due to current overload.