摘要:
An eddy current probe array is disclosed comprising a plurality of spatially correlated eddy current probe elements sufficiently disposed within a flexible interconnecting structure to collect a discrete plurality of spatially correlated eddy current measurements for nondestructive near surface flaw detection. A plurality of precisely fabricated, substantially identical elements being sufficiently distributed can accommodate inspecting an area of conductor covered by the active width of the array in a single uni-directional scan. The array structure can flexibly conform to accommodate inspection of large, irregular, curved conductive surfaces which cannot be inspected by conventional means.
摘要:
An operating circuit for use with a magnetoelastic force/pressure sensor provides for changing the current flow through at least one sensor coil at a frequency responsive to the magnitude of a force impingent upon the sensor. The sensor operating circuit operates in a manner to prevent the sensor magnetoelastic core from being driven deeply into saturation, thus providing an operating circuit with a reduced current drain. A number of embodiments, including clock-driven and self-clocking (toggling) circuit providing digital and/or analog outputs are described.
摘要:
A circuit is provided for controlling energization of the start winding of an alternating current motor whose shaft is divided into a number of angular segments equal to the number of poles of the motor. A shaft pulse is generated each time one of the angular segments rotates past a predetermined point. A line pulse is generated for each half cycle of line voltage. The shaft pulses are multiplied by the denominator of a selected trip-out ratio while the line pulses are multiplied by the numerator of the trip-out ratio. The multiplied shaft and line pulses are provided to an up/down counter which counts the shaft pulses down and the line pulses up. During the counter overflow condition, the circuit connects the start winding to the line voltage source. During the counter underflow condition, the circuit disconnects the start winding from the line voltage source.
摘要:
A control system for regulating electrical power input to the resistive heating elements of an electric heating apparatus, including domestic cooking appliances, is provided which employs at least one piezoceramic relay device. The electrical power is applied with the piezoceramic relay device responsive to control signals and with the control circuitry being directly and ohmically connected to the power source. In one embodiment, the control system employs individual piezoceramic relay devices for power regulation to the individual heating elements while in different embodiments a single piezoceramic relay device regulates power input to a pair of the heating elements. A method of operating the controlled apparatus in such manner and an apparatus having such control system are also disclosed.
摘要:
A force/flash pressure sensor utilizes a stack of annular rings of a magnetoelastic material. One major stack surface is supported at a plurality of points having substantially equal angular displacement therebetween. A member, moving along the axis of the ring stack responsive to an axial force, or pressure, to be measured, presses a different set of points against the opposite stack surface, to distort the ring stack and alter the magnetic flux density saturation magnitude thereof. The plurality of points in abutment with each of the opposite major stack surfaces is advantageously equal; a number of different configurations for applying force (pressure) along the axis of the ring stack are described.
摘要:
A current sensor for use with a conductor with known cross-sectional characteristics is an electronic circuit having a monolithic Hall-effect element disposed substantially perpendicular to the conductor first major surface. A conductive loop substantially encircles the element and is oriented such that its flux is substantially orthogonal to the element surface. An amplifier sets current flow in the loop responsive to minimization of the differential Hall voltage across element. The loop current, at null, will be related to the conductor current by the ratio of the conductor flux path length to the loop flux path length.
摘要:
A microprocessor-based relay system is used in combination with relay contactors and a control circuit therefor to protect an electric motor from overload currents in addition to phase faults, ground faults, load losses, and load jams. The microprocessor is provided with a data base comprising thermal characteristics of the motor during heating and cooling. The heating data comprise current versus time curves stored as a look-up table for which each data point represents a thermal limit, i.e., the maximum time the motor is permitted to operate at a particular current level. The cooling data comprise motor cooling rates. Phase currents are sampled at preselected fixed time intervals during a predetermined period thereof, and an average motor current value is calculated therefrom. A thermal sum, which is initialized at zero upon first starting the motor, is adjusted depending on the average motor current value relative to a predetermined overload current value. The average motor current value is used as an index to the heating curve look-up table. If the thermal sum exceeds the corresponding thermal limit in the look-up table for a predetermined time interval, then an overload condition is indicated, and the relay is tripped.
摘要:
A conventional non-dimming ballast for fluorescent lamps is modified to achieve a 100:1 dimming ratio by connecting a switching module to the ballast. The switching module switches current to and from the fluorescent lamps under control of a level control, resulting in the desired light output. The switching module may be connected either in series or in parallel with the lamps.
摘要:
A circuit is provided including a reactor for operating a fluorescent lamp from AC line voltage and including a high frequency inverter for operating the lamp from a battery upon failure of line voltage. The inverter also serves to start the lamp during normal conditions, that is, when AC line voltage of sufficient value is available to the lamp.
摘要:
A wall box dimmer is connected to a conventional fluorescent lighting system for providing a wide range of dimming. Overvoltages generated during chopping of the AC input waveform are dissipated and the lighting level is modified to reduce the overvoltages. DC power for the control electronics is derived from the voltage across the dimmer.