Abstract: An electrostatic instrument for measuring particle concentrations and possibly sizes in aerosols, such as an Electrostatic Low Pressure Impactor or Differential Mobility Analyser suffers from errors which limit the useful response bandwidth of the device. The invention minimises or eliminates these transient errors which are caused by changing particle concentrations in the aerosol. A system may be added to an otherwise conventional instrument to compensate for the transient effects based on a model of the charge production mechanism. Alternatively, a screening electrode placed over the sense electrodes in the instrument, and held at controlled electrical potential difference, is added to the instrument to eliminate the effect. A third embodiment adds compensating electrodes which provide a direct measurement of the transient effect which can be subtracted from the signal.

Abstract: A biological cell test method and apparatus employs a conventional perforated cell carrier which has a plurality of holes. Each hole has two metal electrodes. A cell is disposed in the hole to contact the two electrodes. The electrodes are connected to electric current or voltage. The electric current or field flows from one electrode through the cell to another electrode. Through the inherent impedance, inductance or capacitance of the cell, the presence or property reactions of the cell may be detected.

Abstract: A system for determining a level of a combustible fuel in an aircraft fuel tank with a thermistor bead comprises: apparatus for disposing the thermistor bead at a height in the fuel tank; a temperature sensor disposed in the fuel tank for measuring a temperature in proximity to the thermistor bead; a first circuit for conducting a constant bias current of less than thirty milliamps into the fuel tank and through the thermistor bead; a second circuit for generating a reference voltage in proportion to the measured temperature of the sensor; a third circuit for measuring a voltage across the thermistor bead in response to the bias current, and also coupled to the second circuit for detecting the dry/wet state of the thermistor bead based on the measured and reference voltages and generating a signal indicative thereof; and a fourth circuit for determining the level of fuel in the tank based on the bead height and dry/wet state signal.

Abstract: A system and method for testing a cathodic protection system includes a cathodic protection rectifier configured to apply a voltage across a pipeline and a reference point. The method includes measuring a magnitude of an output voltage of the cathodic protection rectifier, transmitting to a site remote from the rectifier, the measured output voltage magnitude using a cellular control channel, receiving the transmitted measurement at the remote site, and using the transmitted measurement to determine whether the cathodic protection system is operational.

Abstract: A method of precisely determining velocity of propagation and the location of a fault on an electric transmission line, using a system of high frequency transmitter and receiver combinations to monitor and detect high frequency bursts produced by the transmitters and by faults, including memory and analysis capability to store and analyze high frequency data before and after a detected fault.

Abstract: A monitor includes a display panel, a displaying circuit, a connector and a self testing circuit. The self testing circuit has a testing signal generator, a switch circuit and a detecting circuit. When the detecting circuit detects the video signals transmitted from the computer, the detecting circuit switches off the switch circuit so as to avoid the testing signal generated from the testing signal generator being transmitted to the input port of the displaying circuit. When no video signals transmitted from the computer are detected, the detecting circuit switches on the switch circuit to allow the testing signal generated from the testing signal generator to be transmitted to the displaying circuit.

Abstract: A method and apparatus for detecting electromigration at its outset includes a pair of conductive traces deposited on a substrate in an integrated circuit. A multiplicity of conductors are connected along the length of the traces. Current is passed through the traces and the resistances of the traces from one conductor connection to the next are continually monitored by observing the voltage drop from one conductor to the next. The connection of the conductors to the traces may be less than one micrometer apart. When resistance changes as a result of the onset of electromigration, the exact location can be determined and studied in optical or scanning electron micrographs.

Abstract: A pin configured to be disposed within a probe is provided. The probe may be configured to measure a property of a conductive layer. The pin may include a contact surface which may be substantially planar. The pin may also include a first portion extending from the contact surface. A cross-sectional area of the first portion, in a direction substantially parallel to the contact surface, may be substantially equal to a surface area of the contact surface across a length of the first portion. A system configured to measure a property of a conductive layer is also provided. The system may include a mounting device and at least two probes coupled to the mounting device. The probes may be configured to measure the property of a conductive layer. In addition, the mounting device may be configured such that one of the probes may contact the conductive layer during measurement.

Abstract: A method and apparatus for providing information from a speed and direction sensor is disclosed. The method and apparatus detect the presence of a ferromagnetic object as it moves past a sensor. The sensor determines speed and direction information regarding the ferromagnetic object, and further provides information relating to the environment surrounding the sensor or object, such as the status of an air gap between the sensor and the moving object, and the temperature of the environment in which the sensor or object is disposed.

Abstract: Described are a system and method of detecting an improperly connected cable in a storage system. A system includes an enclosure having boards. Each board of the enclosure has a communications port that receives a message identifying a redundant backend network to which that board is connected. The enclosure determines whether the system has an improper cable connection by determining from the messages whether the boards are connected to the same redundant backend network.

Abstract: A method of reliability testing is disclosed. A critical breakdown resistance of a device is determined. The test structure is subjected to stress conditions and electrically tested. The critical breakdown time of the test structure is recorded when the operating resistance of the test structure is equal or smaller than the critical breakdown resistance.

Abstract: A digital envelope detector (consisting of both hardware and software) that provides accurate measurements of changes of peak values of an AC signal (these peak values constitute the envelope of a signal). Such accurate envelope measurements are required to optimize the accuracy and selectivity of chemical sensors. A signal of interest is compared to each of a set of accurately calibrated reference voltages provided by a digital to analog converter. A digital logic circuit and software respond each time the signal fails to exceed the current reference voltage. In that event, relevant data (time or cycle count) are digitally recorded and a new reference voltage is installed. The process is repeated until the desired range of change of signal is measured.

Abstract: A current comparator technique is applied to four-terminal resistance measurements for obtaining a highly accurate AC resistance bridge at power frequencies of 50 Hz to 60 Hz. Active circuits are used to establish equal voltage drops between the potential terminals of the two resistances being compared. The bridge is suitable for measuring resistances from 10 &mgr;&OHgr; to 100 k&mgr;&OHgr;. A cascading technique using two two-stage current transformers provides extension of the ratio range to 100,00,000 with a maximum applied current of 10,000 A. The bridge features measurement with a resolution of 0.1×10−6. The total combined uncertainty (2&sgr;) of the bridge including the range extenders, at power frequencies, is estimated to be less than 5 &mgr;&OHgr;/&OHgr;.

Abstract: A sensing element (2) for sensing a fluid (50) composition and a method of using the sensing element (2) are provided. The sensing element (2) includes an electrode base (36) having a first electrode (4) and a second electrode (6) disposed on the electrode base (36); the first electrode (4) and a second electrode (6) being electrically isolated one another except through an external circuitry (64); the first electrode (4) and the second electrode (6) defining a gap (42) between one another such that electrical conduction through a fluid (50) within the gap (42) is proportional to the composition of the fluid.

Abstract: A test probe for a high-frequency device having an electronic circuit with two or more contact regions. The test probe comprises two or more signal probe tips. Each signal probe tip has a contact surface area for contacting one of the contact regions of the device. A ground probe has a ground contact surface with a surface area substantially greater than the contact surface area of the one signal probe tip for contacting another one of the contact regions of the electronic circuit. The ground probe is positioned between at least two of the signal probes.

Abstract: A method for locating a speed sensitive ground condition in a field winding of an electromagnetic synchronous machine having a rotor and an excitation circuit, the method including: sensing a magnetic flux generated by the field winding, while accelerating the rotor and activating the excitation circuit; detecting a cyclical aberration in the magnetic flux occurring during revolution of the rotor, and determining a position in the field winding corresponding to the cyclical aberration and identifying that position as a location of the speed sensitive ground condition.

Abstract: Electronic device for monitoring the temperature of a medium ensures that the temperature has not reached pre-established index limit values. The device includes contacts for closing an electric charge flow circuit when the temperature reaches an index limit value, an electric charge storage component connected to the charge flow circuit when the contacts close, the charges remain stored as long as the temperature does not reach one of its index limit values, and is able to flow through the charge flow circuit when the circuit is closed by the contacts, the charge storage not returning to the charge state which they had before the charge flow circuit closed if the latter opens again, and a provision for reading enabling the charge state to be determined.

Abstract: A probe having a built-in reference plane for use with TDR testing includes a conductive sheet member such as a wire mesh which is attached to a ground input of a TDR system. The conductive sheet is located proximate the tip of the test probe and extends radially from an axis of the test probe thereby providing its own reference ground plane.

Abstract: Accurate and stable measurement of the dielectric constant of the substance or a mixture of substances by the use of measuring the delay through a transmission line imbedded in the substance as a delay means with compensation for signal degradation brought about by conductivity of the substance. The substance for which the dielectric constant is to be measured is introduced between or about the elements of the transmission line so as to vary the propagation or delay of the signals through the transmission line.

Abstract: Methods and apparatus to detect terminal open circuits and short circuits to ground in inductive head write drivers are presented. A exemplary method is provided for detecting a short-circuit condition at at least one of a pair of write head terminals of a write driver, the write driver producing a write current that, when passed through a inductive head assembly coupled to the pair of write head terminals, polarizes the inductive head according to a direction of the write current. The method includes the step of generating a first current that is proportional to at least a portion of the write current that flows in a first direction into a first write head terminal of the write driver. A second current is generated that is proportional to at least a portion of the write current that flows in a second direction, opposite the first direction, into a second write head terminal of the write driver.