Abstract: The high speed operational recurring signature evaluation provides digital sub-systems including a data compressor and a controller. These subsystems are employed with a portable service processor (PSP) which is a standard piece of test equipment in this art. The controller interfaces with the host logic tester (PSP) to provide the repetitious detail and complex digital control requirements for programming the data compressor in response to digital instructions received from the logic tester. A unique serial data pattern corresponding to a proper signature from a node under test generated in real time at the relatively high operating speed of the board under test is generated by the data compressor.

Abstract: A vibration densitometer including a synchronous detector, a threshold detector, an integrator, an electromagnetic bridge driver, a piezoelectric crystal pick-off, a voltage controlled oscillator (VCO), a phase detector responsive to the crystal output and that of the VCO to control the VCO frequency and/or phase to provide an output signal of a frequency to energize the driver.

Abstract: Differential and static pressure transducers are provided with piezoresistive elements connected in Wheatstone bridges on the 100 surface of a silicon chip over a diaphragm etched into the chip from the back. A thin disk diaphragm is used for differential pressure (DP) and a thicker annular diaphragm around the disk diaphragm is used for static pressure (SP) measurements. Two of the elements opposite each other in each bridge are produced along one crystallographic direction (110), and the other two are produced along an orthogonal crystallographic direction (110). Extra elements are produced for each pair to permit selection of a more closely matched set of four elements. A plurality of DP diaphragms with different diameters and respective bridges are provided along with a multiplexer for selecting a DP bridge in order to provide different ranges of sensitivity for the differential pressure measurements.

Abstract: An analyzer for natural gas to determine the existence of and concentration of wanted and unwanted sulfur compounds and odorizing agents.

Abstract: In order to determine the vortex shedding frequency, from which the fluid flow rate may be calculated, an optical beam, such as produced by a laser, is passed through a fluid, transversely to a vortex street therein, and modulated in dependence on the alternate high and low velocity regions comprising the vortex street. The modulated signal is detected and "cleaned" of noise by filtering with a first (high) band-pass filter of a center frequency f.sub.c, such that the first filter output comprises an amplitude modulated signal of carrier frequency f.sub.c modulated by the vortex shedding frequency, that is the frequency of oscillation of the power spectra between the respective curves for the high and low velocity regions. The first filter output is demodulated and filtered by a second (low) band-pass filter, whose output is of a frequency comprising the vortex shedding frequency.

Abstract: An electro-mechanical load sensor is in the form of a mechanical resonant system with electrostatically coupled electrodes. The mechanical system is formed from a silicon wafer by a selective etching process and comprises a filament of between two terminations 12 and 13 carrying transverse plates M.sub.1 and M.sub.2. Electrostatic (capacitive) coupling to plate electrodes E.sub.1, E.sub.2, E.sub.3 in a self-exciting circuit drives the system. The resonant frequency for angular S vibrations with plates M.sub.1 and M.sub.2 in anti-phase varies with applied load L and is thus a measure of this load.

Abstract: A totalizer of the decade counter type or the like which, when being pulsed, tends to drain a battery, where the battery and totalizer are remotely located. The battery thus needs to have a long life because of its remote location. The same is effected by a circuit including a voltage regulator which holds average power constant, at least from pulse to pulse.

Abstract: A pH electrode which is capable of withstanding repeated exposures to sterilizing temperatures. An electrode body having a pH sensing member is at least partially filled with a bed of electrochemically inert particles. After an internal reference is inserted into the particle bed, the bed is injected with a quantity of electrolyte which is sufficient to establish continuity between the sensing member and the internal reference, but which is not sufficient to produce destructive internal pressures when the electrode is subjected to sterilizing temperatures. The electrode is completed by forming a seal between the electrode body and the internal reference.

Abstract: An improved nondispersive infrared gas analyzer having at least one pneumatic or Luft-type detector and at least one black body type detector located one behind the other along the optical axis of the analyzer. In the preferred embodiment, a black body detector is exposed to radiation from a sample cell through an intervening pneumatic detector. The pneumatic detector absorbs radiation at specific infrared wavelengths, while the black body detector absorbs radiation substantially uniformly at all wavelengths. Signals from the pneumatic detector and the black body detector are combined electronically in an improved signal processing circuit to provide an output signal that is substantially free of the effects of disturbing influences such as infrared source intensity variations, mechanical vibrations and shock, and the presence of interfering compounds.

Abstract: An improved source assembly for use in infrared gas analysis instruments. A rotating reflector having a generally conical shape is provided with a reflective interior surface. An infrared source directs infrared radiation against the reflector from a predetermined number of fixed directions each of which is generally perpendicular to its axis. One or more blocking members, which are aligned generally parallel to the axis of the reflector, pass between the source and the reflective surface as the reflector is rotated. In operation the source assembly generates a plurality of chopped beams of infrared radiation which, because they emanate from a single source and are reflected from the same reflective surface, have a highly uniform intensity. This uniformity of intensity allows the source assembly to illuminate a plurality of sample cells that are distributed circumferentially about the axis of the reflector.

Abstract: An improved liquid sample injection valve having a metering rod for receiving a sample of a test liquid in a sample loading assembly and delivering that sample to a sample evaporating assembly that is connected to a gas chromatograph. In the sample loading assembly there is provided a sample chamber housing having an improved sealing and mounting arrangement that provides a high degree of thermal isolation between the sample loading and evaporating assemblies. A novel mounting arrangement for the metering rod allows the latter to be conveniently changed without disassembling the valve. The sample evaporating assembly is provided with a flow control element which minimizes deal volume and provides improved sample removal and evaporation characteristics.

Abstract: A membrane type amperometric gas sensor is provided with a pressure equalization passage between the exterior and interior of the cell in which the electrodes are located. Cell fluids move into and out of the passage as necessary to maintain the pressure inside the cell substantially equal to the pressure outside the cell over a wide range of pressures and temperatures. A movable fluid plug or seal located in the passage protects the fluids inside of the cell from contact with the gas being sensed and from the atmosphere for all permissible values of pressure and temperature.

Abstract: An improved method for producing an electrode assembly for use in electrochemical gas sensors. A plurality of conductors are attached to one surface of a generally circular electrode blank. These conductors are passed through respective conductor routing holes in an electrically nonconductive mounting member. After the electrode blank is attached to the mounting member, predetermined sections of the electrode blank are cut away to divide the blank into a plurality of electrically isolated regions that are connected to respective conductors. The cut-away sections may then be filled with an electrically nonconductive filling material to provide the electrode assembly with a smooth, flush surface.

Abstract: A molded one-piece housing for use in fabricating conductivity cells. An electrically nonconducting housing includes an internal partition which divides the interior of the housing into a first region for receiving a test liquid and a second region for receiving a plurality of electrical conductors. Openings through the partition provide passages through which measuring electrodes may project into the first region to establish cell constants of the desired magnitude. These openings are so shaped that they establish a liquid-tight seal between the housing and the electrodes during insertion. By means of this seal the electrodes are held firmly in place during the assembly of the cell. This seal also permits a potting compound to be introduced into the second region without leaking onto and thereby affecting the electrical characteristics of the electrodes.

Abstract: A multi-channel instrumentation system is provided wherein signals from selected electrode pairs are sequentially connected to the isolated input of a common signal amplifying path. The electrode pair selecting means is included in a portable head box which may be placed adjacent to the patient to be tested. Included in the head box are facilities for testing the impedance of any selected one of the patient electrodes and providing a visual indication of the magnitude of such impedance. The head box also includes facilities for selecting a group of patient electrodes which are connected together and used as an average or reference potential for one input of the common signal path. Facilities are also provided for calibrating the common signal path by applying a d.c. calibration signal to the input thereof by means isolated from system ground.

Abstract: A communication system for communicating digitally encoded information from a remote transmitting station to a central receiving station. The central station supplies d-c operating power to a remote station through a d-c power distribution line. A voltage regulator at the remote station receives the d-c operating power and derives therefrom a constant d-c voltage for powering the circuitry of the remote station. A digital transmitter at the remote station changes the magnitude of the current drawn through the voltage regulator, in accordance with a message to be transmitted, and thereby changes the current in the power distribution line without affecting the voltage supplied to the circuitry of the remote station. These line current changes are detected and decoded at the central station to reconstruct the transmitted message.

Abstract: An ion activity or concentration analyzer including an ion selective electrode, a reference electrode and a flow-through electrolytic cell. A sample liquid enclosure conducts a flow of an aqueous sample past the anode and cathode electrodes of an electrolytic cell that is polarized to generate hydrogen and hydroxyl ions. The ion selective and reference electrodes are so positioned, with respect to the cathode electrode, that the hydroxyl ion concentration is increased in the vicinity thereof. This increased hydroxyl ion concentration causes a reduction in the hydrogen ion concentration and thereby substantially eliminates the interfering effect of hydrogen ions on the operation of the ion selective and reference electrodes.

Abstract: A method and apparatus is disclosed for selectively determining by non-dispersive infrared techniques the concentration of a gaseous constituent in a sample gas mixture while determining and discounting deleterious effects of spectrally interfering gases in the sample gas mixture.