Abstract: An improved electronic particle counter is described in which the electrodes and at least part of the signal processing circuitry are integrally formed on the pane in which the orifice is located. The pane is formed from a wafer of sapphire of the grade customarily used in the manufacture of silicon-on-sapphire integrated circuits. A silicon layer is first formed epitaxially on one side of the wafer and integrated circuits are then formed in the silicon layer using conventional photolithographic techniques. Illustratively, the integrated circuits provide the same particle counting and particle sizing functions that are available in separate packages with state-of-the-art particle counters. An electrode is formed on the same side of the wafer as the integrated circuit by converting some of the epitaxial silicon to a conductive polysilicon or by depositing a metallic layer; and the electrode is connected to the signal input lead of the integrated circuit.

Abstract: By a method of and an apparatus for determining the degree of freshness of fish or other pieces of meat a pair of electrodes of an electrode assembly are brought into contact with the pieces of food, and the degree of freshness is determined electrically by determining the phase angle of the impedance which the tissue of the piece of food in question represents by inducing an alternating current into the tissue of the piece of food and by determining the delay of the voltage produced by the current in relation to the current.

Abstract: Changes in the ultrasonic properties of fiber-reinforced plastics during the curing process are monitored by a marginal oscillator to determine the degree of cure. The plastic sample and transmitting and receiving transducers serve as a narrowband acoustic resonator and are placed in the feedback loop of a variable gain amplifier; using gain control the system is allowed to marginally oscillate. The resonant frequency of the sample and amplifier gain are related to the velocity and attenuation of sound in the plastic and are determined by measuring the received signal frequency and amplifier gain control voltage. The system has frequency locking means to track changes in resonant frequency during the cure cycle.

Abstract: A sensor and method for performing immunoassays using surface acoustic waves on a piezoelectric crystal is provided. A specific antigen or antibody is bonded to the surface of the piezoelectric crystal and its resonant frequency in a blank solution is determined. The sensor is then exposed to a test solution containing an antigen or antibody corresponding to the substance bonded to the surface of the crystal. As the antigen and antibody react, the resonant frequency of the crystal is altered. This change can be correlated to determine the amount of antigen or antibody in the test solution. A nonreactive reference sensor can also be used to compensate for any nonselective adsorption.

Abstract: A slide motion sampling valve for use with a particle study device and carrying an expansive type microsyringe having a minimum trapped volume. The sampling valve is formed of a slidably movable member carrying a trapping volume, an expansive element and ejection port in the form of a fine aperture, and a stationary element sealingly engaged with said movable member and carrying an opening leading to the entrance of the sheath flow arrangement. The valve operates between a conditon where the ejection port and the opening are aligned and a condition where communication to the entrance is blocked whereby to isolate the trapping volume from said entrance except during ejection of the predetermined amount. One embodiment described employs a linear sliding motion while another embodiment employs a rotating sliding motion.

Abstract: A proton conductor gas sensor operable at room temperature for detecting hydrogen or carbon monoxide, and a gas detecting method using the sensor. A pair of electrodes connected to a proton conductor are short-circuited to cause protons to travel through the conductor utilizing the difference in activity between the electrodes or the difference in gas permeability between the electrode and an atmosphere containing the gas to be detected. The potential difference produced in the interior of the conductor by the travel of the protons is obtained as the output of the sensor. This output is in proportion to the concentration of the gas and low in humidity dependence.

Abstract: Flow measuring apparatus comprising a probe (1) coupled via a coaxial cable (2) to control circuitry with a current to voltage convertor (10), absolute value circuit (12), auto zero switch and integration (11, 27) and voltage to current circuit (18) yielding an analog output, corresponding to flow at the probe.

Abstract: An electronic device for feeding an ion pump with two different tensions and for improved measuring of the pressure in the pump, the two different tensions being a normal operating tension and a lower tension at which a correct measurement of the pressure can be made in a pressure range up to beyond 10.sup.-10 torr. through a transformer whose primary or secondary winding is divided into two sections that can be connected and separated by switches controlled by oscillator circuits. Alternatively feeding at two different tensions can be obtained by feeding to the primary winding of the transformer a pulsed tension having a rectangular wave form and a high frequency controlled by a field effect transistor having an isolated gate. A sampling and holding circuit permits the pressure to be measured only in the conditions of feeding at the lower tension.

Abstract: The sensor 1 has its point of operation towards the Townsend discharge zone, and the collection of ions causes an increase in the current passing through it. The electrodes of the sensor are formed by wires bent in the shape of an alpha.

Abstract: A method and apparatus by which the degree of wear and useful life limitations of a drill, end mill or other types of metal removal tools can be detected. The method is based on the short circuit current, open circuit voltage and/or power that is generated during metal removal by the utilization of an insulated rotary tool bit to which electrical contact is made by a non-rotating conductor and an insulated or non-insulated workpiece, with an external circuit connecting the tool and workpiece through a measuring device. The generated current, voltage or power shows a sharp increase or change in slope upon considerable tool wear and/or at the point of failure.

Abstract: An improved method and device for measuring magnetic particles in a liquid wherein a known amount of liquid is contacted with a bed of ferromagnetic fibers maintained in the magnetic field of a magnet with sufficient strength to substantially completely magnetize said particles for a time long enough for said particles to migrate to and be substantially completely captured by said fibers and having a magnetic flux sensor positioned between a pole face of said magnet and said bed wherein the distance from said sensor to the fibers farthest from said sensor is not greater than about 6 millimeters.

Abstract: A particle suspension from a process is introduced into a measuring vessel 1 and caused to rise above a screen 4 whereupon the streaming potential of the suspension is determined by measuring the voltage across the screen at alternately different, relatively low pressures. The measurements may be carried out continuously with the measuring vessel being rinsed between measurements. The apparatus comprises a vertical U-shaped measuring vessel 1 in which a horizontal screen plate 4 in one leg 3 defines a measuring chamber 9, the other leg 2 being supplied with the suspension. Valves V4-V8, V10 are provided to alternately subject the vessel to different measurement pressures, and to provide a high rinsing pressure. Adjacent its center the screen plate supports electrodes 5, 6 for measuring the voltages between particle suspension and filtrate, and an electrode 11 is associated with the screen plate for measuring the conductivity of the suspension.

Abstract: A method and device for measuring the amount of magnetic particles in a fluid such as ferrous wear particles in the lubricant of a machine. The particles are entraped by contacting a volume of the fluid with a means to entrap the particles and magnetized by subjecting the entraped particles to a magnetic field. The amount of magnetic particles entraped is measured by measuring the magnetization of the entraped and magnetized particles.

Abstract: A method and apparatus for measuring the unsteady sedimentation potential of particle in a suspension comprising: inserting at least a portion of the suspension of particles in a cell, the cell having a first electrode and a second electrode; vibrating the cell to accelerate the particles in suspension; and measuring the unsteady sedimentation potential of the particles across the first and second electrodes. The cell is vibrated at a frequency in the range between 0.0001-50 khz.

Abstract: An electrical pulse apparatus for measuring impurities in ultrapure water includes a deaeration device connected to the conduit line supplying electrolyte to the hollow detector so as to deaerate the electrolyte and enable bubbles formed by electrolysis at the electrodes to be readily redissolved and thus increase measurement sensitivity and speed.

Abstract: A device for monitoring environmental exposure includes an element whose electrical properties change, in a predetermined way, in response to the environmental exposure. The element may be part of a tuned circuit or of a shield for a tuned circuit. In either case, when the tuned circuit is interrogated, preferably by an r.f. or microwave signal, it emits a signal whose intensity depends on the electrical properties of the element. Thus, an incremental environmental exposure can be measured by a change in the signal intensity. The device is particularly useful for monitoring the condition of perishable materials, because it can be located with the perishable inside a packaging material during both storage and interrogation.

Abstract: Apparatus for the determination of the location and/or distance traveled by a piston in a cylinder. This apparatus can easily be integrated into shock absorbers, vibration dampers and pneumatic springs, and exhibits a high degree of insensitivity to at least electrical interference, therefore being particularly well-suited for operation under unfavorable ambient conditions. As a result of the use of the most modern semiconductor technology and a suitable geometric arrangement, a very good resolution can be achieved, along with an automatic recognition of the direction of piston travel. Such an apparatus has a number of semiconductor elements; in one embodiment, in a beam fastened inside the cylinder or, in another embodiment, in the hollow piston rod. These semiconductor elements are arranged so that, over the axial length of the piston stroke, the distances between two neighboring semiconductor elements correspond to a specified measurement value resolution.

Abstract: An apparatus for monitoring a cathodic protection system on a structure which is positioned in water such that a portion of the structure is beneath the surface of the water, such apparatus comprising: an insulating means positioned adjacent to the structure below the surface of the water; a metallic body positioned adjacent to the insulating means so that the body is electrically insulated from the structure; means for electrically connecting the body to the structure at a point above the surface of the water; and means for measuring the amount of current flowing through the electrical connecting means.

Abstract: A method of monitoring gases using electronic conductivity changes in ordd organic semiconductor films comprising an insulated substrate fabricated to an interdigital microelectrode and coated with a vapor sensitive semiconductor film. Variations in current flow caused by vapors interacting with the film are indicative of the vapor type.

Abstract: A method for the analysis of particles in suspension in a fluid having a conductivity different from that of the particles, in particular a method for the analysis of blood particles is disclosed. The method includes the following steps: passing the fluid through an orifice, applying an electronic signal across the orifice, and producing electronic pulses corresponding to the changes in the signal level caused by the passage of the particles through the orifice. The invention is also concerned with a device for carrying out the method.

Abstract: A machine condition diagnostic system is provided wherein machine components are labelled with indicator materials. A normal level of indicators in the lubricant will be established. The lubricant is monitored and periodically or continually sampled to determine the presence of abnormal levels in the amount of indicator material. Since each component or components performing a similar function will be labelled with the same indicator, the presence of a particular indicator in abnormal amounts in the lubricant will direct the machine operator to the precise location requiring repair or replacement.

Abstract: The invention provides a new method and apparatus for the detection of non-conductive particulates in molten metals, such as aluminum, gallium, zinc and lead, that can be liquified and drawn into a suitable refractory container. The passage into the container is of very small diameter (about 300 micrometers for aluminum) and it forms part of a current path between two electrodes carrying a current of about 1 to 500 amperes. The path is surrounded by liquid metal which forms an effective Faraday cage screening the path, enabling the passage of a particulate of about 15 micrometers or larger to produce a voltage pulse between the electrodes of greater than 5 microvolts, which is detectable above the inevitable background noise, which is of about that value.

Abstract: A field emission chemical sensor for specific detection of a chemical entity in a sample includes a closed chamber enclosing two field emission electrode sets, each field emission electrode set comprising (a) an electron emitter electrode from which field emission electrons can be emitted when an effective voltage is connected to the electrode set; and (b) a collector electrode which will capture said electrons emitted from said emitter electrode. One of the electrode sets is passive to the chemical entity and the other is active thereto and has an active emitter electrode which will bind the chemical entity when contacted therewith.

Abstract: The polarized potential at the boundary between a submerged pipe and a medium is measured unaffected by the presence of a distributed IR drop in the medium due to an impressed current from a corrosion protection system. The voltage between the pipe and a reference electrode in the medium is measured when the protection system current is zero. This is accomplished with a sample-and-hold circuit controlled by a trigger signal derived from the input signal and having a variable phase for controlling the phase angle at which the sample is taken.

Abstract: An apparatus for the measurement of the quality parameters of granular materials includes a loader assembly which delivers precise volume samples of granular material to a meter assembly which measures the moisture content. The apparatus also includes a sieve assembly which separates the samples into fractions according to kernel size. A scale assembly weighs the fractions and feeds this information to a computer which controls the apparatus and calculates the moisture content, density and percentage of foreign material contained in the granular material.

Abstract: An arrangement for determining and measuring the position or travel of a piston in a cylinder, e.g., suspension component such as a vibration damper, gas-spring or hydropneumatic suspension, uses a structure having no moving electrical contacts, nor any movable electrical leads. The arrangement measures a variable impedance, e.g., a capacitance which is created by first and second electrodes formed within the suspension component and is distinguished in that the electrodes are fixed and are immovable with respect to each other. Capacitance variation is achieved, for example, by allowing a dielectric medium, such as a ceramic or epoxy resin cylinder to enter between two electrodes, the extent of the entry of the dielectric medium being made to be proportional to the relative travel of the piston in the cylinder. In a variation, an additional electrode forming a fixed reference capacitance with the first electrode is provided.

Abstract: The present invention relates to a wheel electrode suitable for use with a device for making an electrical survey of a structure contained in an electrolyte. The wheel electrode includes a chamber which contains electrolytic solution and a porous rim. The rim includes a dielectric rim structure having at least one recess in its axial surface, a plurality of apertures passing through the rim structure into the recess, and at least one porous member securable in the recess and having a predetermined rate of permeation. A metal electrode is positioned in the chamber in contact with the electrolytic solution. An elastic porous rim cover is securable about the rim for making contact with the electrolyte. The rim cover is adapted to carry an electrically conductive solution to the electrolyte during wheel rotation. Generating mechanisms are spaced about the wheel electrode at predetermined intervals for generating a series of electrical signals as the wheel electrode rotates.

Abstract: A contactlessly, measuring arrangement for determining the position of a piston in a suspension component such as a vibration damper, gas spring or hydro-pneumatic suspension. In one embodiment, the piston and/or the piston rod of the suspension component and a further electrode are mounted inside the cylinder of the suspension component to form a variable capacitor which, with the aid of other circuitry, measures the position of the piston. The further electrode preferably is in the form of a tube extending from the base of the cylinder into a hollow cylinder formed within the piston rod which receives the tube. In the capacitive embodiment, additionally, there may be provided a further tube within the first tube to form a reference, second capacitor which is sensitive to pressure and temperature in the same manner as the first capacitor.

Abstract: A method and apparatus for removing foreign matter, including debris and deposits and air bubbles from a flow cell of a particle study device. The apparatus includes a chamber with an aperture containing unit at one end and sample and sheath introduction mechanisms at the other end to supply respectively, a sample suspension of particles and a particle free liquid. The chamber has a waste orifice positionally disposed to provide a turbulent flow of particle free liquid within the chamber upon simultaneous injection and exhaustion of the particle free liquid into and out of, respectively, the sheath introduction mechanism and the waste orifice, to remove any air bubbles in the chamber and its adjacent aperture area.

Abstract: An apparatus for measuring the degree of sensitization of metal articles comprises an electrochemical cell in which the potential of a test-piece of the article with respect to a reference electrode is made to vary linearly with time by feeding currents of suitable intensity from the passivation field to the activation field by means of the counter-electrode; a pair of electrodes moves along the test-piece surface with the respective electrode ends kept equidistant and disposed along an axis substantially perpendicular to the test-piece surface, one of them being in contact with said surface; by measuring the potential difference of this pair of electrodes as a function of their position, the local degree of sensitization of the test-piece is obtained.

Abstract: A device useful in diagnostics in which a biochemical species is attached to the surface of a sensor, especially to the gate of a field effect transistor. In such a "BIOCHEMFET" it has been a problem to attach two or more biochemical species to the surface of the sensor, especially to the gates of a multi-gated FET. It has now been found possible to bond a group having a photoactivatable function covalently to the sensor surface, photo-expose the resultant modified surface selectively, e.g. through a mask, and bond the biochemical species, e.g. a hapten, antigen, antibody, lectin or enzyme, to the photoactivated function. In this way the biochemical species becomes attached in selected areas only. In view of the success of this technique realized under conditions of miniaturization, the invention makes possible "printed circuits for proteins".

Abstract: In order to measure the values of the electrical charges (2) carried by a surface S of a dielectric sheet (1), one uses a device consisting of a first electrode or probe (S) facing the surface S, a second electrode (4) applied against the back surface of this sheet, means (F) to displace laterally the probe with respect to the sheet and means (5) to measure the charges (6) induced on this probe.In addition, by means of acoustical, optical or electrical methods, one subjects the surface S to deformation localized in very small spots p (of an area inferior to the one defining the spatial resolution of the measurement) during very short times and repeatly at frequence high enough and in such a way as to have some overlapping of the spots sequentially deformed.

Abstract: A superior moisture probe and technique for assaying liquid and gas streams for moisture concentration in the parts per million (ppm) range, comprises an emf source connected across a pair of adjacent conductive probes separated by a sulfonated aliphatic fluorocarbon membrane, the combination being immersed in the fluid of interest, or in a sealed headspace associated therewith, the former being the preferred mode. With a D.C. emf, the resistance change of the probe, or a value proportional therewith is monitored, and from that value H.sub.2 O concentration is deduced. With an A.C. emf, capacitance, A.C. resistance, and/or impedance of the described probe structure varies proportionately with the concentration of H.sub.2 O in the membrane, and is monitored directly or indirectly to deduce H.sub.2 O concentration.

Abstract: Disclosed is a method wherein osmotic activity of biological cells immersed in a suspension solution is induced by an osmotic or lytic shock and is monitored in an electronic volume sensing particle analyzer of the Coulter Counter.RTM. type, the method including the steps of passing a high frequency current and a low frequency current through an aperture of said particle analyzer to create detectable signals for classifying the cells into populations of unaltered, altered, and ghost cells.

Abstract: In the formation of a paper web from stock fed to a Foudrinier wire, the Zeta Potential is an important parameter. A measure of Zeta potential is made by measuring the streaming potential developed in a vertically-arranged cell having a horizontal mesh therein on the underside of which a pad of fibres and fines is formed by pumping stock into the lower part of the cell. Electrodes located in the cell above and below the pad are used to obtain a measure of streaming potential at a given pressure differential across the pad. A pressure transducer is mounted in the lower part of the cell. Corrections are made for temperature and conductivity by sensors in the stock feed path to the cell. A microprocessor control and measuring circuit is disclosed which sequences valves for controlling the flow of stock and flushing fluid to the cell and which measures the relevant parameters.

Abstract: Rapid and accurate whole blood analysis measurements are made with analysis systems of the potentiometric type that employ restricted diffusion type liquid junctions where the whole blood sample is flowed past sensing electrode and liquid junction at a velocity of at least one centimeter per second during a data acquisition interval that is at least twenty-five milliseconds in duration.

Abstract: A particle analyzer apparatus comprising a flow cell having a flow chamber wherein a flow of liquid suspension, having individual particles entrained therein, proceeds along a predetermined path; a pair of electrodes are disposed on opposed sides of the predetermined path, one of the electrodes having an end with a width parallel to the predetermined path that is less than the length of a given particle, the end of the electrode being positioned in close proximity to the predetermined path; energizing source for providing an electrical field between the pair of electrodes that traverses the predetermined path; and a particle pulse detector for detecting particle pulses caused by the particles passing through the electric field.

Abstract: A particle analyzing apparatus for studying a stream of membrane-sheathed particles in liquid suspension wherein, for a given particle, a first particle pulse signal is obtained from a first sensing aperture having a first low frequency electrical field with an intensity below that causing particle electrical breakdown; a second particle pulse signal is obtained from a second sensing aperture having a second low frequency electrical field with an intensity equal to or greater than that causing particle electrical breakdown; a third particle pulse signal is obtained from one of the sensing apertures by having a high frequency electrical field therein or, alternatively, from a third sensing aperture having a third low frequency electrical field with a second and different intensity equal to or greater than that causing particle electrical breakdown.

Abstract: For measuring the deformation capacity of erythrocytes use is made of a sample vessel that is walled off into two spaces by a piece of foil with a pore therein. One such space is filled with buffer solution with erythrocytes and the other is filled with buffer solution without erythrocytes. A pressure head is produced acting across the foil for causing transit or passage of the erythrocytes through the opening, whose diameter is less than the major quiescent diameter of an erythrocyte so that information on the deformation capacity may be produced by measuring the transit time. This is done by electrodes placed on the two sides of the opening so that changes in the resistance to alternating current by an erythrocyte in transit may be sensed and the transit time taken. After about 200 transits the readings are processed in a processing unit.

Abstract: An electrolysis test station terminal (10) support for use in connection with measurement of electrical properties of an underground pipe (12). The terminal support includes an elongated web structure (21) formed of nonconductive plastic material and including at least one longitudinal rib (17, 18, 19) integrally formed as part of the web structure. A hollow core (30, 31, 32) is formed within the longitudinal rib and provides a housing for conductive wire (37, 38) to be concealed therein. An opening in the longitudinal rib provides access to the core to enable physical contact (37a, 38a) for measurement of electrical properties as conducted from the underground pipe through the wire into the terminal support.

Abstract: An E-Log I field computer includes a controlled power supply, timers, and a current level stepping relay for circulating cathodic current through a buried metal structure, interrupting the current to allow the decay of residual polarization of the structure and electrolytes within the surrounding ground, and measuring the circulated current and the voltage of structure relative to the ground. The circulated current, voltage of the structure to the ground, and other parameters of interest, such as, the output voltage of the power supply are printed. Then the current level is increased by the stepping relay, and the process is repeated. When a sufficient number of readings have been taken, the data is plotted as a semi-log graph, resulting in an E-log I curve from which the corrosion current and therefore the cathodic protection voltage can be determined.

Abstract: Apparatus for measuring the quantity of flowable particulate material passing through a conduit; the apparatus including a mounting portion, a flowable material contacting portion, a sensing portion, a circuitry portion and a quantity determining portion; the mounting portion including a support bracket, a transversely disposed bulkhead section affixed to the bracket adjacent the entry end of the apparatus; the flowable material contacting portion including a baffle extending from the bracket adjacent the entry end of the apparatus, the baffle having one end pivotally connected to the bracket, the baffle being pivotable away from the entry end of the apparatus; the sensing portion including mechanically actuatable voltage varying mechanism, the voltage varying mechanism being mounted on the bracket adjacent the pivotal connection of the baffle with the bracket, the voltage varying mechanism being operatively connected to the baffle; the circuitry portion including a converter converting voltage values into pe

Abstract: A circuit arrangement is disclosed for correcting the output of a sensor which experiences changes in sensitivity due to the presence of one or more influencing factors, such as the concentration of a material to be sensed, or the passage of time. The circuit arrangement includes a correction network which generates a simulated sensitivity curve which simulated curve is combined with the output of the signal to produce a corrected output signal which has apparent constant sensitivity.

Abstract: The tester and method for nondestructively detecting nonlinearity faults in conductors includes the application of a composite AC and DC drive signal to the device under test in such manner that nonlinearities in the device under test produce fault signals including second harmonics, due to local changes of resistance caused by ohmic heating. Electronic filters are used to select out and amplify the second harmonic only, eliminating the direct current and fundamental frequency components of the initial test pulse, plus third and subsequent harmonics. The filtered second harmonic signals from the device under test are then phase-compared to a phase-shifted second harmonic signal produced by a frequency doubler from the test signal generator oscillator to cancel out the second harmonic signals from the good conductor; the remaining phase anomaly signals control a threshold detector remaining to provide fault indication.

Abstract: A transducer for measuring particles suspended in a fluid is disclosed. The transducer includes an elongated tubular member having a particle-free fluid conducting channel and an aperture for permitting the flow of a particle containing fluid into the fluid conducting channel. The size of the particles is measured by measuring the impedance variation of the particle containing fluid as it passes through the aperture. Spurious variations of the impedance caused by reentry of the particles into the region about the aperture is prevented by spacing the wall of the channel opposite the aperture so that the particle containing fluid impinges thereon after passing through the aperture and so that the particle-free fluid transports the particles away from the aperture before the particles reenter the region about the aperture.

Abstract: An apparatus for monitoring a cathodic protection system on a structure which is positioned in water such that a portion of the structure is beneath the surface of the water, such apparatus comprising: an insulating means positioned adjacent to the structure below the surface of the water; a metallic body positioned adjacent to the insulating means so that the body is electrically insulated from the structure; means for electrically connecting the body to the structure at a point above the surface of the water; and means for measuring the amount of current flowing through the electrical connecting means.

Abstract: The thicknesses of metallic coatings on a surface is coulometrically measured employing a probe for storing electrolyte solution provided with a power supply and indicating and controlling circuits. The probe comprises a cylinder defining a chamber for storage of electrolyte and having at one end a nozzle of capillary size surrounded by a gasket or cuff adapted to be placed in abutment against the surface to be tested. The opposite end of the cylinder is connected to a source of oscillating pressure which imposes on the electrolyte a corresponding movement against the working surface.

Abstract: Disclosed is a particle analyzing apparatus having a flow cell with an elongated or tube-like aperture for receiving a liquid suspension of particles and for providing a smooth fluid flow therethrough and electric field and current, generated in and essentially limited to a relatively small portion of the aperture, for producing electrical signals when the particles pass therethrough.

Abstract: A hematocrit measuring instrument of the type which determines hematocrit of blood from the electrical resistivity of the blood is provided with a blood resistivity measurement device, an ultrafilter for filtering a part of the plasma from the blood, a filtrate resistivity measurement device for measuring the resistivity of the filtrate from the ultrafilter and an arithmetic circuit for calculating the hematocrit of the blood from the resistivities of the blood and the filtrate. The hematocrit measuring instrument is connected into a circulatory path for the blood outside of the patient's body and continuously measures the hematocrit of the blood from the resistivity of the blood and the resistivity of the filtrate from the ultrafilter.

Abstract: A device for detecting the isoelectric end point in an isoelectric focusing system by electronically integrating, over successive time intervals, a characteristic of the electrical input to said zone as it varies with the increasing resistance of the zone. Most conveniently, the measured characteristic is the current through the zone which, under constant impressed voltage or power, asymptotically approaches a minimum value as the end point is reached.The measured characteristic is continually converted to a sequence of pulses indicative of the value of the characteristic. The end point is indicated when the difference between counts of these pulses over successive time intervals reaches a preselected value. At the end point, provision is made for replacement of the focusing voltage with a lower voltage to keep the ampholytes focused. A signal can be activated at the end point.