Abstract: A high pressure valve for control of the injection of a sample into an analyzer system such as an amino acid analyzer with liquid column chromatography. The valve is designed in such a manner that no rinse solution that is used to cleanse the system after the injection of a particular sample will enter the liquid column. The valve operates in two positions and requires a minimum of movement between the two positions. In one position the valve allows for the injection of the sample into the liquid column. In the second position the valve allows for the entry of only a buffer solution into the liquid column and blocks the entry of any rinse solution that may flow through the system for cleansing after the injection of the sample. No residual rinse solution is allowed to remain within the valve prior to injection of either a sample or a buffer material into the liquid column.

Abstract: Plunger operated pipet operable to execute different lengths of plunger movement during successive fluid pickup and fluid discharge operations or strokes. A stop member is movable between first and second locations in the pipet body to halt plunger movement at two different positions. A drive spring for driving the stop member from one location to the other is energized by a manually operable arming element and is retained in one location against action of the drive spring during a first plunger stroke. A release mechanism responsive to plunger movement during the first stroke disables the retaining means allowing the drive spring to move the stop member to the second location at which position the plunger is halted during the succeeding discharge stroke. The arming element is actuated by and in response to positioning of a replaceable tip on the pipet body.

Abstract: The present invention is directed to a circuit for generating a voltage for compensating the output of a thermocouple. The circuit provides a compensating voltage to enable the thermocouple to be operated with its reference junction at ambient temperature. The compensation voltage varies linearly with changes in the ambient temperature and passes through zero volts at 0-20 C. The compensation voltage is generated by combining a temperature variable voltage developed across one or more semiconductor junctions with a constant voltage of opposite polarity.

Abstract: A display system and method utilizing a common character generator among a plurality of display devices. Each display device generates address signals which are multiplexed and applied to the character generator. The output from the character generator is used to control the visual representation produced by each display device. A graphics memory of picture elements can be addressed for a composite display of graphics and alphanumeric characters by the various display devices.

Abstract: A video display memory expansion system for expanding the graphics memory within the video display. The memory expansion system is suited for increasing the resolution of a graphics display from a low-resolution to a high-resolution display. A video display device is adapted to receive a relatively simple graphics memory expansion accessory to thereby easily and inexpensively provide the increased graphics memory capability.

Abstract: A solution of the type comprising cobalt ammonium sulfate and sulfuric acid. The solution is characterized in that it comprises from about 0.020 to about 0.040 N H.sub.2 SO.sub.4.Also, a method for checking the linearity of response of a spectrometer or spectrophotometer. The method is of the type comprising measuring absorbance (A) or percent transmittance (%T) of a solution versus a blank at a known wavelength. The method is characterized in that the above solution is employed therein.In addition, a method for checking photometric accuracy of a spectrometer or spectrophotometer. The method is of the type comprising measuring A or %T of a solution at a specific wavelength. The method is characterized in that the above solution is employed therein.

Abstract: A liner for use in a centrifuge rotor bucket for converting a single cavity bucket into a multicavity bucket to provide separate support for at least two flexible fluid sample containers. The liner has a separation ridge which defines at least two areas in the liner, but allows maximum space for receipt of the flexible containers. Handle means are attached to the liner to provide ease in the removal and insertion of the liner into the rotor bucket.

Abstract: Gain hysteresis exhibited by the photomultiplier detector of a single beam spectrophotometer is reduced by illuminating the detector and applying dynode voltage thereto during the normal "off" or "idle" interval of the spectrophotometer.

Abstract: An elongate straight column for use as a reactor in an analytical instrument. The column contains inert packed material which provides for the necessary flow path length for a fluid stream entering the reactor. Fittings are incorporated onto the ends of the column in such a manner that their width is no larger than the width of the column. The column configuration for a reactor allows more versatility in the type of temperature regulator mechanisms used to heat and cool the reactor.

Abstract: Gain hysteresis exhibited by the photomultiplier detector of a single beam spectrophotometer is reduced by illuminating the detector and applying dynode voltage thereto during the normal "off" or "idle" interval of the spectrophotometer.

Abstract: Plunger operated pipet operable to execute different lengths of plunger movement during successive fluid pickup and fluid discharge operations or strokes. A stop member is movable between first and second locations in the pipet body to halt plunger movement at two different positions. A drive spring for driving the stop member from one location to the other is energized by a manually operable arming element and is retained in one location against action of the drive spring during a first plunger stroke. A release mechanism responsive to plunger movement during the first stroke disables the retaining means allowing the drive spring to move the stop member to the second location at which position the plunger is halted during the succeeding discharge stroke. The arming element is actuated by and in response to positioning of a replaceable tip on the pipet body.

Abstract: A photomultiplier detector protection system and method utilizing a negative feedback loop to maintain the photomultiplier detector output below a predetermined output. The feedback loop comprises a comparator responsive to the photomultiplier detector output and also responsive to a predetermined limit signal. The comparator output is applied to a summing amplifier which also receives a voltage adjust signal. The output of the summing amplifier controls the output of a power supply which is in turn applied to the photomultiplier detector.

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 method for checking noise of a spectrometer or spectrophotometer. The method is of the type comprising measuring absorbance (A) or percent transmittance (%T) of a solution over a period of time. The method is characterized in that the solution comprises from about 0.040 to about 0.090 M nitrite, the nitrite being present as a nitrite ionized constituent.

Abstract: A method and apparatus for determining an insufficient liquid volume. The invention includes an electromagnetic sensing device in a conduit into which the sample liquid is mixed. The electromagnetic sensing device detects the presence of air in the conduit which indicates that an insufficient liquid volume has been aspirated.

Abstract: A safety latching apparatus for a cover of a machine enclosing a round rotatable member. The apparatus includes a latch member, and an elongated flexible control element for sensing the motion of the rotatable member to automatically prevent opening of the cover when the member is rotating. The control element is movable longitudinally so that one of its ends can be brought into contact with the rotatable member and the other end connected to a latching mechanism located adjacent the machine cover. When the rotatable member is stationary, the end of the control element brought into contact with it remains generally rigid to a force in the longitudinal direction allowing the latch member to move to an unlocked position.

Abstract: A method of quench correction in liquid scintillation counting which compensates for the effect of sample quench. A quench corrected pulse height window is established for measuring sample scintillations. A pulse height threshold is established distinguishing regions for which a measure of sample quench, derived conventionally, is either proportional to or not proportional to the actual effect of quench on the sample pulse height spectrum. The quench corrected window is compared with the pulse height threshold, and the relative position of the corrected window is adjusted if the comparison step indicates that the window lies in the region of nonproportionality.

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 method and related apparatus for the determination of a random coincidence count attributable to chance coincidences of single-photon events which are each detected in only a single detector of a scintillation counter utilizing two detectors in a coincidence counting technique. Real and apparent coincidences of pulses are accumulated in a first counting device (28), and all pulses from the detectors (12) are accumulated in a second counting device (38), without regard for coincidence in time. The two counting devices are monitored during at least one random coincidence monitoring time occurring simultaneously with part of a sample counting period. The length and frequency of occurrence of the random coincidence monitoring times can be selected for particular counting measurement applications.

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.