An apparatus for analyzing particles suspended in a fluid. The fluid has electrical properties different from that of the particles. The fluid and particles move from a first fluid containing portion to a second fluid containing portion through a conduit or aperture. A first pair of electrodes, each electrode of the pair being in a respective fluid containing portion. A constricted electrical path is defined between the first and second electrodes, and the path extends along the aperture. At least one other pair of electrodes is positioned in a non-encircling arrangement, and are aligned with each other and transversed to the constricted electrical path. This configuration eliminates many common errors suseptible to other devices.

Apparatus and method for analyzing particles

A conductivity sensor for measuring hematocrit and a sensor housing for a blood analysis instrument using the conductivity sensor are disclosed. The conductivity sensor comprises a seven-electrode conductivity measurement cell in which three symmetric pairs of electrodes are arranged on opposite sides of a central electrode. The central electrode is connected to an AC source and the outermost pair of electrodes, which provide a return path for the current, are maintained at a ground or reference potential. The two inner pairs of electrodes measure the voltage drop along the current flow path. This arrangement confines the measurement current and potential within the sensor chamber, thereby preventing the sensor from interfering with other electrochemical sensors that may be provided in the blood analysis instrument. The sensor housing provides a linear arrangement of flow cells defining a fluid flow path through the housing. The conductivity and other sensors are each located within an associated cell to form a wall portion of the flow path. The housing arrangement is simple to assemble and provides a flow path which resists fouling and is readily flushed out.

Planar hematocrit sensor incorporating a seven-electrode conductivity measurement cell

This invention provides an improved system for monitoring and recording cell cultures. A method for measuring a delay period for an alternating current voltage applied across a pair of pins improves the stability of measurements made with the improved system. A method for applying a voltage across a pair of pins which avoids exceeding a pre-established voltage avoids the possibility of damaging and/or destroying cells while monitoring their culture.

System for electronically monitoring and recording cell cultures

The invention relates to apparatus as disclosed for example in US Pat Nos 4,555,662 and 4,600,880 for on-line particle determination in molten metals, wherein a sample of the molten metal is drawn by a vacuum through a calibrated passage in the side-wall of a heat-resistant tube while a current is established through the passage between two electrodes on either side thereof The passage of non-conducting particles through the orifice produces pulses whose magnitude and rate indicate respectively their size and the number of particles per unit volume The electrodes and their leads form an interference-receiving antenna so that the wanted test signal, whose signal/noise ratio is inherently low, is subject to interference from neighbouring sources, such as motors, fluorescent lamps and particularly induction furnaces The invention provides for the production of a cancellation signal to reduce the unwanted interference component in the test signal by means of a cancellation antenna suficiently close to the detector electrodes to receive substantially the same signal, the antenna either feeding the cancellation signal to a differential amplifier also fed with the wanted signal, or being connected in series with the interference antenna The cancellation antenna can comprise a loop mounted on the head that supports the two electrodes

Apparatus for particle determination in liquid metals

Devices and methods for contactless heating of a fluid in a chamber using a high frequency alternating potential are described At least two electrodes are coupled to the chamber such that the alternating potential is coupled to the fluid inside the chamber and heats the fluid A control loop derives a signal from the alternating potential and uses the signal to control the alternating potential The devices and methods described determine temperature and/or conductivity of the fluid using the signal

High frequency contactless heating with temperature and /or conductivity monitoring

A particle counter, of the type utilizing a Coulter(R) type aperature and a suction flow path downstream from the aperture, has a pair of electrodes on both sides of the aperture. A current is provided from the downstream electrode to the upstream electrode and pulses in the resulting voltage across the aperture are monitored to detect the passage of blood cells through the aperture. A grounded electrode is placed in the downstream flow path at a position near the package panel to isolate the cell counter from external electrical noise signals. An isolated high input inpedance amplifier is coupled to provide the monitored voltage to an inserted electrode positioned between the downstream aperture electrode and the grounded panel electrode. Because the inserted electrode and downstream electrode are then at the same voltage, no current flows through that portion of the flow path.

Ian D. Gilbert

Papers

Isolation circuit for blood cell counter