Abstract: Two controllers in a cascade control system are decoupled to avoid interaction by modifying the error signal to the primary controller in response to changes in the error signal to the secondary controller. The response is developed by a network which models the primary process. A signal developed from the output of the primary controller is fed forward to modify the manipulated variable. The modifying network is a model of the reciprocal of the dynamics of the secondary process. Also, the adjustment performed by the primary controller on the set point of the secondary controller is delayed in accordance with the product of the secondary process model and the reciprocal feedforward model.

Abstract: A histogram of the volume of the particles in a sample of fluid-suspended particles, including those in the submicron region, can be obtained by using an incident light beam having a wavelength approximately twice the average particle diameter in each of the ranges of particle sizes making up the histogram. The 90.degree. scatter from the sample is measured in two orthogonal polarizations. The first polarization has its electric vector perpendicular to the plane containing the point of observation and the incident light beam and the second is parallel to that plane. The magnitude of the light flux having the second polarization is subtracted from that having the first polarization in each range to give a measure of the volume of the particles in that range.

Abstract: Measurement with a three-lead resistance thermometer uses two current sources to set up a current I in the thermometer element and each of its potential leads while a current of 2I is established in the current lead with all currents being in a direction such that the currents in the potential leads are in the same direction with respect to the thermometer element. A standard resistor is connected in series with one potential lead and a voltage measurement is made across the potential leads, including the standard resistor, to provide a measure of the temperature being sensed by the resistance thermometer. The current sources each utilizes a voltage divider connected between one terminal of a constant potential source and another terminal along with a follower circuit connected to receive an input from an intermediate point on the voltage divider.

Abstract: A string of short pulses is impressed across the input circuit of a multipoint recorder and a pulse magnitude detecting circuit. If the input circuit is open, the magnitude of the pulses appearing at the pulse magnitude detecting circuit is higher than would be the case if the input circuit were completed by a normal input device. The pulse magnitude detecting circuit is operable to apply to the measuring circuit of the multipoint recorder a positive potential whenever the pulse detecting circuit detects pulses of a magnitude indicating that the input circuit is open. As a result, the multipoint recorder is driven upscale to its limit where the particular point which is open-circuited is identified by a printed indicia.

Abstract: A thermopile type radiation detector for use in radiation pyrometry having small size and high performance in which the thermopiles are formed by evaporating the thermocouple leads onto a thin substrate together with a pattern distribution of thermocouple junctions that produces an output that is more representative of the distributed radiant energy impinging on the hot junctions of the thermopile. The thermopile performance is improved also by the incorporation of relatively large reflecting areas associated with the region of the thermopile where the cold junctions are located.

Abstract: A servo system is disclosed which produces a mechanical position varying in accordance with variations in an electrical input signal. The input signal is applied by an amplifying channel to one input of an error amplifier. The input signal amplifying channel includes an integrating amplifier and a voltage limiting device at the input to the integrating amplifier so that the signal applied to the error amplifier has a limited rate of change. A negative feedback gain determining loop is included in the amplifying channel so that at balance the signal applied to the error amplifier is directly related to the input signal. Applied to the other input of the error amplifier is a signal representative of the positional output from the servo system to form a second rebalanceable loop system.

Abstract: An electrolytic cell for measuring the concentration of a species such as oxygen is constructed by depositing closely spaced interleaved inert electrode surfaces on the surface of an insulating substrate and covering the electrode surfaces with a thin film of electrolyte and permeable membrane. The electrolyte is selected so that the species being measured is generated at one electrode surface and consumed at the other with no net reaction in the electrolyte. Alternatively, a cylindrical configuration may be formed by closely winding two thin electrode wires about a cylindrical base and covering with an electrolyte and a membrane.

Abstract: A supporting means for a flexible graphite cloth heating element comprised of a conductive bar having a dovetail shaped slot and a mandrel shaped to fit within the slot and to hold a loop of the graphite cloth heating element therein.

Abstract: A rotating mask having three spatial filters is placed in the light path after a laser beam is passed through a sample having a collection of particles. The mask sequentially filters the light scattered by each particle to produce at a detector receiving the filtered light a response which is in accordance with the second, third and fourth power of the particle diameter. The detector integrates the response to all particles in the laser beam and the signal resulting from the integration of the response due to the individual filters is used to calculate statistical parameters. The mean of the area distribution is calculated as the third power response divided by the second power response.

Abstract: An improved bi-polar dual slope analog to digital converter having an automatic zero offset correction circuit using a high gain D.C. amplifier inserted between the output of the integrating amplifier and the input of the comparator amplifier, having both positive and negative reference potentials, and having a delay compensation circuit, for compensating delay produced by circuit elements in the signal path, coupled between the reference potentials and an input of the integrating amplifier.

Abstract: A method for detecting a plateau for a measured variable by comparing the clock pulses from a dual slope analog to digital converter which are counted during consecutive pairs of conversions. The counter is decremented during the first conversion and incremented during the second. If the counts are detected as being identical within a prescribed number of counts an accumulator is incremented. A predetermined number of successive increments of the accumulator indicates a plateau. The accumulator is cleared whenever the counts of a pair of conversions are not within the window.

Abstract: The far-field diffraction pattern produced by illuminating a collection of particles with a coherent light source is spatially modulated by a filter mask having a first aperture. The aperture is shaped to pass a total light flux proportional to a particular moment of the particle distribution over a certain particle size range. Light flux is passed by another aperture at greater or lesser radii and adjacent the first aperture. That flux is effectively subtracted from the flux passed by the first aperture as by subtracting the resulting signals produced by a photo detector at different times in response to the flux passed by the filter. The difference signal provides a measure of the particular moment within the same limits of accuracy but over a wider or narrower particle size range, respectively.

Abstract: There is disclosed a Fraunhofer plane spatial filter design for use in filtering the forward scattered light from a collection of particles to obtain an indication of the sum of the radii of the particles as a direct function of the total diffracted light flux passed by the filter.

Abstract: A differential pressure measuring device of the three diaphragm type is disclosed in which the measuring in diaphragm is isolated from the substance being measured by a pair of sealing diaphragms. The measuring diaphragm is included in a cell assembly that provides overrange protection for the measuring diaphragm and isolation of the measuring diaphragm from the influence of static pressure induced housing strains.

Abstract: A removable control signal is provided which varies as the product of a gain constant times the control error and has means for increasing the gain constant as a time integral of the error. The integral is reset to zero, thus making the gain constant zero, when the error crosses zero to avoid an excessive build-up of the value of the control signal as when the error fails to promptly correct itself.

Abstract: A spectrochemical analyzer utilizing a transparent medium such as quartz which has a color reagent coating the surface. When light is directed into the transparent medium, the magnitude of internal surface reflection varies with the change in absorptivity resulting from a color change in the reagent in response to a change in the chemical condition of the sample. By measurement of the light transmitted by the transparent medium the chemical condition of the sample is measured.

Abstract: A thermal print head produced by a multilayer process is disclosed. Six of the seven bar-segments of the figure "8" produced by resistive deposits are bounded on the outside by conductive deposits and on the inside by the internal areas of the figure "8" while the seventh is bounded by the internal areas of the figure "8". The peripheral segments are heated selectively by conduction between selected bar-segments and associated internal areas at a particular time while the internal areas are energized to heat the central segment at another time. Each internal area has a single electrical connection to the external switching circuitry.

Abstract: A hot stylus using a mandrel of soft material having good heat conductivity and good electrical conductivity is used to carry heat to the writing end of the mandrel. That end fits in an aperture of a jewel bearing surface which rides on the heat sensitive paper. The mandrel is soldered in a groove along a thermistor having a positive temperature coefficient. The mandrel also provides one electrical connection to the thermistor. The other electrical connection is by way of a foil contact soldered to an opposite face of the thermistor. That assembly is potted and assembled on a circuit board which provides the electrical leads from the stylus body to which the foil is soldered and from the mandrel itself.

Abstract: An assembly for insertion in a bath of molten material to form therewith an electrochemical cell for determining the concentration of a constituent of the bath. The assembly is of the type including a body structure of refractory material from which protrudes a first electrically conductive element providing means for establishing an electrical connection with the bath and a reference electrode structure separated from the bath by means of a rigid electrolyte material. Reference electrode structures of this general type may be comprised of a closed end tube of electrolyte material or a tube of electrically non-conductive refractory material having a pellet of electrolyte material closing the immersion end thereof to separate the material of the bath from the means establishing a reference potential.

Abstract: A flow-through thermal detector for determining the temperature change resulting from a reaction in a fluid stream includes a pair of parallel fluid paths one of which carries the fluid stream in which the reaction occurs while the other carries a similar fluid without the occurrence of a reaction. The detector includes a temperature sensor for each path. The first of the sensors is mounted to sense the temperature of the reacting stream after said reaction has occurred while the second of the sensors is mounted to sense the temperature of the non-reacting stream at a point in its flow path comparable to that at which the first sensor is mounted. A heat shield is provided surrounding the parallel paths and the heat shield is controllable to a predetermined temperature. Preheating of the streams is carried out by a preheating means positioned within the heat shield to receive the fluid stream entering the shield.