Abstract: A digital-to-analog converter is disclosed which employs a ladder configuration comprising a series of R1-R2-R3 stages in which resistors R2 and R3 are selected so that mathematically the combined resistance of R2 in parallel with R3 is equal to twice the resistance of R1. The resistance of resistor R3 is on the order of 3 to 30 times greater than the resistance of resistor R2. These resistors are configured in stages with FET switches.

Abstract: A method for measuring the impedance of a transmission line. The length and D.C. loop resistance of the line are measured. A pulse is transmitted along the line, the pulse having a duration greater than the time required for it to propogate from its source to the end of the transmission line and reflect back to the source. The transmitted and reflected pulses are monitored and the resultant readings converted to a gross impedance measurement. The measurement is then corrected for the "dribble up" effect. The magnitude of the correction is a function of D.C. loop resistance of the line. The corrected measurement is an accurate measurement of line impedance.

Abstract: Apparatus (1) for performing an electrical test on a cable (3) used in local area networks (LAN's). A source (37) produces electrical signals transmitted through the cable. A resistance circuit (43) is interposed between the source and the cable. The amount of resistance interposed by the resistance circuit is adjusted using an adjustment circuit (67). A sensor (71) senses a characteristic of the signal and determines when that characteristic has a value representing an inpedance match between the source and the cable. The sensor circuit provides a command to the adjustment circuit to thereafter maintain the point of adjustment at which the impedances are matched.

Abstract: Improved accuracy in solution conductivity or resistivity measurment uses a center-sampling technique in which an AC drive is applied to a conductivity cell and the conductivity cell voltage is sampled during a predetermined time interval in the center of a half cycle drive waveform. The effects of cell capacitance, and particularly the electrode-solution capacitive, are compensated by periodically sampling during a second time interval which is different from the first interval. Based upon the difference between the sampled voltages in the first and second intervals, a correction to the measured conductivity or resistivity is made to compensate for capacitance induced errors.

Abstract: An improved sensor for dissolved oxygen measurement comprising a body having an electrolyte reservoir and electrolyte contained therein and an opening for communication between the exterior of the body and the reservoir and an anode and cathode concentrically disposed in the body adjacent the opening. A thin polymeric membrane permeable to oxygen and impermeable to the electrolyte seals the opening. The working surfaces of the anode and cathode, that is the surfaces adjacent the membrane, are spaced apart from the membrane to define an electrolyte space between the working surfaces and the membrane. A noble metal screen is disposed on the working surface of the anode. Preferably the screen completely covers the anode working surface and a portion of the screen which would normally overlie the working surface of the cathode is cut away so that the cathode working surface is unobstructed.

Abstract: Apparatus for removably connecting a calibrating gas chamber to the body of an electrochemical sensor consisting of corresponding members carried by the sensor and the gas chamber, each member defining a contact surface that cooperates with the contact surface of the corresponding member to removably secure the surface together so that connection of the chamber is accomplished by contacting the surfaces of the corresponding members and the chamber can be removed when calibration of the sensor is finished for connection to another sensor or reconnection to the same sensor at a later time. In a preferred embodiment the corresponding members are composed of Velcro fabric.

Abstract: The present invention relates to a gas chromatography assembly comprising a high mass, thermally conductive body provided with at least one cell in which is disposed a resistance filament for the detection of a sample gas. Lines are provided for communication between the cell and sample gas and carrier gas from chromatographic separation columns. The conductive body is adapted to carry the separation columns in heat transfer relationship therewith. In accordance with the present invention, the assembly components, including the interior of the cell and the separation columns are heated with a single heating element, which is controlled by a single heating element control means. The temperature of the environment of the sensor, switching valves and the separation columns, are thus controlled through a single constant temperature control system.

Abstract: A solid state sensing element comprising a nonporous, structurally stable, electrically insulating substrate on which is disposed spaced apart pairs of electrodes for contact with moisture. A hygroscopic electrolytic material is located in close proximity to the electrodes as by coating the electrodes with the hygroscopic material. A catalyst is deposited in close proximity to the electrodes and is electrically insulated therefom. The electrodes are connected to a source of potential and current measuring instrumentation. Moisture is trapped by the hygroscopic material and electrolyzed at the electrodes. The catalyst recombines the hydrogen and oxygen thus formed to water so there is no net consumption of water by the element and equilibrium is established at the sensor surface and the atmosphere adjacent the sensor surface.

Abstract: Apparatus for calibrating a conductivity instrument having a conductivity cell and a conductivity measuring instrument operatively associated with the conductivity cell, includes a conduit for supplying high purity water to be measured; a first flow line for supplying the high purity water from the conduit to the conductivity cell; a second flow line for supplying the high purity water from the conduit to the conductivity cell; a mixed bed ion exchanger in the second flow line for de-ionizing the high purity water flowing through the second flow line; and a valve which selectively supplies the high purity water to the conductivity cell, from either the first flow line to provide a conductivity measurement of the high purity water or the second flow line to calibrate the conductivity cell.

Abstract: An improved electrochemical cell is described which comprises at least one electrode having increased signal strength achieved by treating at least the working surface of the electrode with a coating of a polytetrafluoroethylene and a catalyst metal selected from the group consisting of platinum and the oxides thereof in an aqueous oligosaccharide solution. Following coating, the electrode is heated to a temperature below the sintering temperature of the polymer to thermally convert the oligosaccharide in the presence of the catalyst metal and drive off the conversion products. An electrode thus treated exhibits a substantially inproved signal strength as compared to an electrode of the same construction which has not been treated in accordance with the invention.

Abstract: A normal pH sensitive glass electrode is deactivated by exposure to thermal treatments at relatively high temperatures of approximately 190.degree. C. for predetermined periods of time until the nominal electrode sensitivity is reduced to very low levels such that the output potentials of such deactivated glass electrode approach the characteristics desired for a theoretically perfect reference electrode.Additionally, a method of forming a deactivated pH glass electrode including the steps of exposing a normal pH or other ion sensitive glass electrode to high temperatures in the order of 190.degree. C. or higher for predetermined periods of time is disclosed.

Abstract: Apparatus for generating a constant current, comprising a storage device for storing a voltage corresponding to the constant current, the storage device including a resistor-capacitor filter and having an input and an output; a Zener diode for supplying a constant voltage; a first high off-state impedance device for connecting the Zener diode to the input in response to a first actuation signal; a second high off-state impedance device for connecting the input to a source of discharge potential in response to a second actuation signal; a microprocessor for supplying the first actuation signal to the first high off-state impedance device for a first time interval and the second actuation signal to the second off-state impedance device thereafter for a second time interval, and then providing no first and second actuation signals for a third time interval much greater than the combined first and second time intervals; and a voltage-to-current converting circuit connected to the output and having a high input im

Abstract: An improved non-dispersive infrared analyzer. The analyzer includes an improved source assembly having a reflecting element with a concave annular reflecting surface, and a circular heating element which is located substantially at the focal region of the reflective surface. The analyzer also includes an improved detecting assembly having a reflecting element with a paraboloid reflective surface that focuses radiation on one or more detecting elements that are located out of the field of view of the reflecting element. Because of the better collimation and more efficient use of its infrared beam, analyzers which include these source and detecting assemblies may use sample cells having non-reflective inner surfaces, and thereby provide output signals of improved stability.

Abstract: A push button switch assembly comprising a plurality of push button switch actuators includes a flexible, unstretchable electrically non-conductive belt for permitting only one of the push button switch actuators at a time to be in its activated position while the remaining switch actuators are all in their deactivated position. The switch assembly cover includes a molded detent spring for maintaining a switch actuator with a shaft having suitably axially spaced detents in its activated position when one of the detents engages the spring. The switch actuator comprises movable contacts aligned to engage respective stationary contacts disposed in the base of the switch assembly when the switch actuator is in its activated position. The belt is strung over tensioning risers disposed in a predetermined path on the base of the switch assembly at each side of a switch actuator. The switch actuator shaft further includes a groove for confining the belt therein.

Abstract: A grounding device for connecting the body of a person to a ground point to drain off electrostatic charge from the body of the person. The device includes a conductive band worn on the wrist of the user, a connecting cable and sensing and indicating circuitry for verifying the electrical continuity of the grounding device.

Abstract: A monitoring port for use in measuring the intensity of the ultraviolet radiation within an ultraviolet water purification system. A UV transparent transmitting member is sealably mounted for inward, outward, and rotational movement movement with respect to a UV lamp. A locking arrangement including a tapered elastomeric gripping member and a tapered metal tightening member assures that the transmitting member may be locked in place at any desired distance from the surface of the UV lamp. A positioning arrangement such as distance indicator or a series of positions stops, may be employed to facilitate the positioning of the transmitting member at any of the selected distances.

Abstract: An improved solid state electrode system for measuring the pH of fluids at temperatures as high or even higher than that corresponding to the critical point of water (374.2.degree. C.). A stabilized metal oxide based ceramic member having a predetermined thickness is coupled to a first metallic conductor by a uniform, solid oxygen-free electrolyte to serve as a pH sensing electrode. A body of an electrochemically inert material, which preferably comprises a stabilized metal oxide based ceramic member having a lesser thickness or a greater porosity, is coupled to a second metallic conductor by a similar uniform solid electrolyte to serve as a reference electrode. Together the pH and reference electrodes form an electrode system that is suitable for use in applications in which the temperatures and/or pressures of the test solution preclude the use of conventional electrodes. A variety of configurations and compositions are disclosed which allow the electrode system to be fabricated in an improved manner.