Abstract: A fault detection circuit for a plurality of three-phase loads uses a wye-connected reference load as a benchmark. The voltages at the centerpoints of the loads to be monitored are monitored and the largest monitored voltage is identified. This largest voltage is compared with the voltage of the centerpoint of the reference load. The comparison is affected by faults which do not affect all loads equally (as by a short or open in one of the phases of one of the loads) and is unaffected by faults which do affect all loads equally (as by changes in voltage of one of the phases of the source).

Abstract: An apparatus for detecting speed sensor failure in an overspeed protection device is disclosed. The apparatus comprises a plurality of tachometers having outputs for indicating the speed of rotation of a machine relative to plural setpoints. If the comparison indicates that certain conditions exist, then a sensor failue is indicated. The apparatus may also be employed to detect a failure of, or loss of power to or within, one of the tachometers.

Abstract: A voltage monitor and method enables the monitoring of a DC input voltage. The input voltage is continuously scanned and compared to a predetermined threshold. The result of the comparison is periodically stored in a shift register along with previous scan results. When a predetermined number of stored scan results indicate an out of range input voltage, a digital output changes state to provide indication of the abnormal condition.

Abstract: A circuit arrangement for monitoring two operating voltages of different polarity detects and indicates the deviation of either operating voltage from its nominal value beyond a predetermined tolerance limit. A transistor is provided, whose base is connected to the positive operating voltage across a first zener diode and to the negative operating voltage through a first resistor, and whose emitter is connected to the negative operating voltage through a series connection of a second zener diode and a second resistor, and to a reference potential across a diode.

Abstract: An apparatus and method are disclosed for measuring and displaying the percentage of ac voltage ripple present on a direct current input voltage. In addition, the apparatus can be set to activate alarms and trip relays when the percentage of ac voltage ripple meets or exceeds a preset value.

Abstract: In a power monitor circuit, AC power-line voltage is converted by a DC power supply to a regulated DC voltage. The DC power supply shuts down itself in the event of a failure therein. The output of DC supply rises from zero to a specified value in slow response to power-on state and drops to zero in slow response to a significant drop in the AC voltage. A rectifier-filter converts the AC voltage to a nonregulated DC voltage. The output of the rectifier-filter rises in quick response to the power-on state and drops in quick response to the significant AC voltage drop. If the output of DC power supply drops below a specified theshold due to AC power-line failure or due to its own failure, a DC low-voltage signal is generated. If the output of rectifier-filter rises above a specified low level a first AC transitory signal is generated and if it drops below a specified high level a second AC transitory signal is generated.

Abstract: In a switch with pre-alarm means (101) having pre-alarming apparatus (20, 21) and an indicator (103) for alarming that value of current flowing on a load is above a predetermined alarming level, output of the pre-alarming apparatus is held at a predetermined level after the value of the current once becomes above the alarming level by self-holding function of thyristor (CR) even when the value of the current becomes below the alarming level after that.

Abstract: A power supply voltage monitoring circuit for use in a semiconductor circuit which is used with a plurality of power supply systems and is operable by switching the high and low power supply voltages, includes at least two power supply lines, a reference voltage source, a first comparator, a second comparator and a switching transistor disposed between the first comparator and second comparator. The first comparator operates under a threshold value of a supply voltage which is an intermediate voltage between the high and low power supply voltages. The second comparator receives a voltage to be compared with a reference voltage supplied from the reference voltage source and the switching transistor changes, in response to an output from the first comparator, a voltage to be compared by the second comparator. An alarm signal indicating as to whether the supply voltage is normal or abnormal is obtained at an output of the second comparator.

Abstract: An apparatus and method for using an output device such as an LED to show the approximate analog level of a variable electrical signal wherein a modulating AC waveform is superimposed either on the signal or a reference voltage, both of which are then fed to a comparator which drives the output device. Said device flashes at a constant perceptible rate with a duty cycle which varies in response to variations in the level of the input signal. The human eye perceives these variations in duty cycle as analogous to variations in the level of the input signal.

Abstract: A device is disclosed for controlling a variable electric signal. A first switch receives the monitored variable electric signal at its input. A second switch receives a first limit electrical signal for the monitored signal and a first minimum reference for the first limit electric signal. A third switch receives a second limit electric signal for the monitored signal and a second maximum limit reference for the limit electric signal. The first switch delivers at its output: the monitored signal when it is between the output signals of the second and third switches; the output signal of the second switch when the monitored signal is greater than the latter signal; and the output signal of the third switch when the monitored signal is less than the latter signal.

Abstract: The present invention is a monitor that detects generator core 12 hot spots where the insulation between ferromagnetic sheets is breaking down by monitoring rotor 10 shaft voltage. The difference between the differential shaft voltage at each end of the rotor 14 produces a voltage signal that changes as the core 12 malfunctions. By comparing signal samples over time, core failure can be detected. Spring loaded rotor shaft brushes 20 and 22 connected to differential isolation amplifiers 24 and 26 obtain the voltage between ends 16 and 18 of the rotating shaft and nearby frame, and a differential amplifier 28 produces the difference between the shaft end differential voltages which is the shaft dissymmetry voltage. An analog-to-digital converter 30 produces digital values of the dissymmetry voltage which can be converted into a voltage frequency spectrum by a Fourier Transform routine executed by a computer 32 or analyzed directly.

Abstract: An apparatus for a signal processing system connected to a power supply having an output level and receiving a clock signal, that is responsive to the output level of the power supply, generates control signals for use as interrupt signals, reset signals and warning signals to the system. The apparatus comprises a detector for generating an undervoltage signal while the output level of the power supply is below a prespecified threshold; a circuit for supplying a programmable signal indicating a programmable threshold; a comparator connected to the power supply and receiving the programmable signal, for generating a voltage threshold signal while the output level is below the programmable threshold; and a programmable logic circuit. The programmable logic circuit receives general purpose inputs, the clock, the undervoltage signal and the low voltage signal, and generates the control signals.

Abstract: The method and apparatus allows the detection and indication of anomalies in the operation of the ignition system of an internal combustion engine including a plurality of spark plugs, each of which receives a periodic high-voltage pulse output by a high-voltage generator in operation. The method includes the steps of:detecting the pulses generated by the high-voltage generator,comparing the peak values of each pulse detected with first and second threshold values, andproducing a perceptible signal when the peak values of the high-voltage pulses fall outside the acceptable range defined between the threshold values.

Abstract: The test apparatus of the present invention tests the power supply on a military aircraft, which power supply provides power to missiles carried by the aircraft. The apparatus tests for an overvoltage condition, wherein the power supply output exceeds the maximum allowable voltage of the missiles. The test apparatus includes an electrical connector for interfacing the test apparatus with the aircraft power supply, and an electrical comparator that compares the voltages from first and second inputs. The first input is clamped to a voltage which is representative of the maximum voltage limit of the missiles and the second input is tied to the output of the aircraft power supply so as to vary with the power supply output. The comparator activates a warning lamp when the second input voltage exceeds the first input voltage to warn an operator of an overvoltage condition.

Abstract: A fluid temperature monitoring system is characterized by an adjustable variable voltage divider for selecting a desired temperature range, a temperature detector for detecting whether the fluid temperature is above, below, or at the desired range, and a temperature indicator for emitting three different temperature indicating signals in accordance with temperatures above, below, or at the desired temperature range.

Abstract: A warning device (10) is provided for use by electrical technicians or the like to indicate the presence of an electrical shock hazard. The warning device is adapted to be worn on the wrists or the like and includes a filtered detection circuit (32,34) for sensing a target signal such as an ac noise signal emitted from an electrical source. When the target signal magnitude exceeds a selected threshold (40), such as when the wearer moves into close proximity with the signal source, the warning device (10) activates an alarm (42,44) to indicate the presence of a shock hazard.

Abstract: Monitoring an electric power distribution circuit having a rated load capacity includes continually sensing an intensity of electric power supplied through that circuit. In response to that sensing a first signal indicating when electric power is supplied through that circuit at a predetermined maximum current usage below rated load capacity is provided. A second signal indicating a safe loading condition is provided when the sensed intensity is substantially below that maximum current usage. A third signal is provided when the mentioned intensity is at a value between the safe loading condition and the maximum current usage.

Abstract: In a circuit tester for applying test voltage to circuit components, a voltage monitor for detecting potentially destructive voltages being applied to one or more additional circuit components other than the components being tested, and in response generating an alarm signal for interrupting the circuit tester, thereby inhibiting generation of the destructive voltages. Monitored input voltages are compared to selectable positive and negative threshold voltages defining upper and lower polarity sensitive destructive voltage limits.

Abstract: A load condition detecting a control system for supplying a load current to a load from a power source wherein, when said load exhibits a short circuit condition, a driving signal controlling the application of high current to the load is immediately pulled down, shutting-off the flow of high current to the load. Thus, even before a short circuit condition is detected by any logic means, the high current is disconnected from the load, preventing any possible damage to the load or other circuitry. The system also detects an open circuit load condition. Upon detection of either an open or a short circuit load condition, the system then blocks the driving signal from being applied to the driving circuitry until the system is reset.

Abstract: A thread motion monitoring system wherein the presence or absence of thread motion for discrete threads is detected and signals developed in terms of the failure, non-thread motion, of selected numbers of threads.

Abstract: A pair of a first and a second R-C integrating circuits connected in series. A first switch S.sub.1 supplies a first combined voltage E.sub.1 +E.sub.3 of a first positive threshold voltage E.sub.1 and a positive initial set up voltage E.sub.3 to a first capacitor in the first R-C circuit, and a second switch S.sub.2 supplies a second capacitor with a second combined voltage of a second positive threshold voltage E.sub.2 with a negative initial set up voltage -E.sub.4. The switches S.sub.1 and S.sub.2 are closed before the input of the signal to be measured. The switches are opened after the input of the signal. A first comparator compares a first discharged voltage output from the first capacitor and the first threshold voltage E.sub.1, and a second comparator compares a second discharged voltage output from the second capacitor and the second threshold voltage E.sub.2.

Abstract: A fluctuating voltage to be monitored is fed to the non-inverting input of a first op amp via a first input resistor; a reference voltage is fed to the inverting input of the second op amp via a second input resistor. The inverting input of the first op amp is taken from a first voltage divider connected between the reference voltage and ground; the non-inverting input of the second op amp is taken from a second voltage divider connected between the fluctuating voltage and ground. The power inputs of both op amps are connected to a positive voltage and ground. The output of both op amps is tied together, with a first feedback loop feeding the tied output voltage to the non-inverting input of the first op amp via a first high-resistance gain-setting resistor, and a second feedback loop feeding the tied output voltage to the inverting input of the second op amp via a second high-resistance gain-setting resistor.

Abstract: Voltage monitor for monitoring the output voltage of a power source which can be connected to a power load, which includes a reference voltage source, comparators for comparing the power source voltage with the reference voltage, switches between the power source and the load, which can be controlled by an output from the comparators, such that the switches can be closed only when the power source voltages are within certain voltage limits and meet certain conditions, and also such that the load is disconnected when the power source voltages go beyond certain voltage or frequency limits. A timing circuit may also be provided for timing various voltage conditions.

Abstract: A circuit breaker warning and control relay provides visual indication of an impending overcurrent condition. Sufficient time is thereby allotted for manual intervention to prevent damage to material and equipment utilized within sensitive manufacturing processes. The relay can be arranged to automatically shut-down selected equipment in a predetermined order for load-shedding implementation.

Abstract: A dot line printer is releasably connected by a control circuit to the output of a monitor which senses variations or faults in the AC line voltage for a computer or the like. Each time the monitor senses any one of the five different voltage disturbances, the information is transmitted as digital data to the printer, which then produces a continuous strip chart or graphical printout of the voltage variations. The printer advances paper continuously and in small increments, while printing thereon six parallel trace lines that extend in the longitudinal or feed direction of the paper. One trace line represents time, and the remaining lines the zero ordinates for five different voltage faults. Whenever a fault is detected, the associated trace line widens to print a horizontal bar. When a power failure occurs and is thereafter restored, a header (indica line) is printed on the paper before printing of the trace lines resumes. The monitor and printer, if desired, may be operated independently of each other.

Abstract: Electrical circuits for detecting intermittent and continuous electrical parameters such as continuity for open or closed circuits, AC power interruption or decrease in frequency, DC power interruption, missing electrical pulses; and voltage, resistance, and current levels that are greater than or less than present high and low limits. This invention also detects temperature and light (illumination) that is greater or less than present limits. The invention has a memory and both a (variable time delayed) automatic, and a manual memory reset. It provides both visual and a defeatable audio indicators or alarms. The advantage of said invention is that it detects intermittent conditions as brief as fractions of microseconds that may occur as frequently as milliseconds apart or as infrequently as days apart; it also detects steady state conditions.

Abstract: The duration of time during which an AC power voltage sinusoidal waveform remains between negative voltage threshold -V1 volts, nominally 5% of negative peak voltage -V2 volts, and positive voltage threshold +V1 volts, nominally 5% of peak positive voltage +V2 volts, is detected. By the change in voltage with time exhibited by a sinusoidal waveform in the region of zero voltage crossing, the expected time duration between voltage thresholds in approximately 5% of one-half period of such sinusoidal waveform. If the actual time between voltage thresholds exceeds (nominally) twice this value, or 10% of one-half period, then a power black-out condition is sensed, and a power fault signal is produced.

Abstract: An alarm apparatus is provided for a freezer having a body and a closure member. The alarm apparatus has an electrical control unit having a power supply input. An alarm device and a temperature sensor are connected to the control unit. The temperature sensor is adapted for mounting in the freezer, for detecting temperatures exceeding a pre-set temperature. A flexible lead is provided for connecting at least two of the control unit, the alarm device and the temperature sensor together. The lead has a cross-section enabling it to extend between the lid and the body of a freezer, while permitting closure thereof. The alarm apparatus can include a second lead connecting the alarm device to the control unit, to enable the alarm device to be placed at a location remote from the freezer.

Abstract: A detection system for a sliding lift or elevator door comprises at least two sensors for monitoring the door opening. The sensors are arranged to detect the presence of a moving irregular shape (e.g. human form) in the doorway to reverse the opening action of the door or, if already open, to prevent the door from closing. A signal compensation circuit is provided to process the output signals from the sensors in a sense to maintain the outputs equal under steady state conditions. This is achieved by using the output of a first sensor as a reference signal. A comparator compares the output of a second sensor with a reference signal and through a feedback loop modifies the output of the said second sensor in a sense to equal the output of the first sensor. The feedback loop contains a delay circuit which is switchable between a long and a short delay. For slow changes in the output of the second sensor the long delay is effective but for first changes the delay circuit is switched to provide a short delay.

Abstract: Disclosed is a supply voltage monitor for detecting the asymmetric decay of one voltage source (V.sub.dd) with respect to another voltage source (V.sub.ss). The monitor circuit (24) includes a resistive voltage divider (26) having a plurality of voltage tap positions (32,35,38). A sensor transistor (40) monitors the voltage between a common connection (16) connecting the voltage sources and the voltage at a desired tap position (38) of the divider network (26). On detecting an imbalance between the voltage sources (V.sub.dd, V.sub.ss), the sensor transistor (40) drives a current mirror circuit (42). The current mirror circuit (42) defines an output (50) of the monitor circuit (24), together with a reference transistor (48) biased by a voltage of the divider network (26).

Abstract: A test circuit for an airbag restraint system provides an accurate determination of the operativeness of a storage capacitor and calculates the resistance of inertia switch resistors. The test circuit provides for parallel testing of the storage capacitor and inertia resistors. The capacitor is tested by discharging and charging the capacitor. The values of the inertia switch resistors are determined by switching known resistive values in parallel with the inertia switch resistors. Based on the monitored voltage values during the switching, resistance values are calculated.

Abstract: An arrangement for detecting the passage of living beings into and out of a surveillance region includes optics which concentrate thermal radiation energy from the surveillance region into a detection zone where an active area of a pyroelectric detector is situated and converts the thermal radiation energy received thereby into an electrical signal. An evaluating device evaluates the electrical signal of the detector to provide an indication of either the entry of a living being from the outside into, or the exit of a person from, the surveillance region from a change in the total thermal radiation energy received by the active area from the surveillance region. The optics may incorporate a mask which prevents thermal radiation from the outside of the surveillance region from reaching the active area of the detector.

Abstract: Apparatus for monitoring fluid flow in dialysis systems include a tube holder for mounting the tube at a predetermined location on a dialysis monitor, a transmitter for transmitting a signal such as ultraviolet light through that location, a receiver for receiving the signal after it has passed through that location, and a sensor for sensing whether the tube is mounted at that location and whether the fluid is contained within the tube in response to the signal received by the receiver.

Abstract: A static monitoring system for use with an electronic manufacturing work area, typically a conventional work bench having an electrical conducting strap for connecting the operator's wrist to earth ground, and including a circuit for indicating when there is an earth ground connection and circuitry for indicating when an electrostatically charged object, such as another human, approaches the work station. An antenna is positioned at the work station spaced from the working surface and from the operator, with the antenna connected as an input to an amplifier circuit which measures the change in electrostatic field strength and hence the approach of a charged object, with an indicator providing a visual or audible alarm or both. An oscillator provides an ac signal to each input of a differential amplifier, with one input connected to circuit ground through a capacitor and the other input connected to a wrist strap or the like on the operator.

Abstract: A low voltage reset circuit includes a first transistor having a base connected to a voltage divider and an emitter connected to the junction of a resistor-diode arrangement such that when the supply voltage falls to a trigger voltage level, the transistor is driven conductive. A second transistor is connected to the collector of the first transistor and is driven conductive therewith for applying a reset voltage to the reset terminal of a microprocessor. The collector of the second transistor is returned through a resistor to the base of said first transistor to provide positive feedback such that the first transistor is maintained in conduction until the supply voltage rises above the trigger voltage level.

Abstract: Lightweight, compact apparatus for detecting sudden changes in the concentration of at least one selected gas provides a warning when said gas concentration increases suddenly. In one embodiment, a chemically sensitive field effect transistor provides a sensing signal two amplifiers having different overall gains and widely different time constants. Detection of sudden gas concentration changes causes the relative magnitudes of the amplifier output signals to be inverted triggering a warning. The apparatus may occupy less than 1.25 cubic inches and weigh less than 4 ounces so that it may be worn by an individual throughout his work place.

Abstract: A method and apparatus for digital phase synchronization to an AC power line is disclosed, having an analog-to-digital conversion providing a digital phase error signal which is processed by an inverting proportional plus integral transfer function and compared to a digital timer to determine the time for the next analog-to-digital conversion.

Abstract: A device for generating an alarm signal in the event of an environmental abnormality has multiple sensors, with a multiplier associated with each sensor, an adder, and a comparator. The sensors are disposed in respective sensing volumes, which may be different. The sensors detect a level of smoke, heat, gas or other environmental abnormality within each sensing volume, and convert the level into an electrical analog signal. The associated multiplier multiplies a coefficient proportional to the sensing volume for the associated sensor with the analog signals from the sensor. The adder adds the outputs of the multipliers. The comparator generates an alarm signal at an output thereof when the output of the adder exceeds a predetermined value.

Abstract: An inexpensive circuit monitors the resistance between a body (e.g., a static dissipative work surface, a tool, etc.) and ground potential, and compares that resistance with high and low resistance values defining a preset resistance range. An operational amplifier is connected to the body and causes current to flow from the body and through the op amp feedback network. A switching arrangement coupled to the operational amplifier alternately switches the amplifier feedback network between low and high resistance values defining lower and upper ends, respectively, of the preset resistance range.

Abstract: This detective circuit detects an abnormal drop of an input voltage of a switching regulator of the flyback system. From the secondary winding of the switching regulator, a constant voltage controlled dc voltage is delivered through a diode. This circuit is provided with a peak voltage charging circuit which detects the peak value of a voltage produced in a direction opposite to the forward direction of the diode, and a voltage comparator which compares the peak value with a setting value. Since this peak value is in proportion to the input voltage, the output of the voltage comparator indicates an abnormal drop of the input voltage.

Abstract: A device for displaying forward and reflected power values simultaneously comprises a plurality of display segments which are switched on in a predetermined sequence to display the forward power and switched off in a predetermined sequence to display the reflected power.

Abstract: A safety line 20 of an aerial ropeway transport installation 10 comprises in one of the stations a safety generating unit 22, which emits a square wave AC signal on the line.In the opposite station the line 20 is earthed by means of a diode 24. The safety generating unit 22 includes a measuring device of the positive and negative voltages at the line terminals to distinguish between a line break and a line short-circuit.A localizer indicates the location of the fault.

Abstract: A safety system and method, for use with apparatus having a conductive member where the apparatus changes the attitude and/or altitude of the conductive member during the operation of the apparatus, includes an antenna mounted on the conductive member which senses an electric field and provides an AC signal representative of the strength of the electric field. The peaks of the AC signal are averaged over several cycles to provide an average peak signal. A reference signal circuit derives the reference signal from either the average peak signal prior to the change in the member's attitude and/or altitude or while the member's attitude and/or altitude is changing. A control device connected to the averaging circuit and to the reference signal circuit prevents further changing of the conductive member's attitude and/or altitude in accordance with the average peak signal and the reference signal when the electric field strength is greater than a safe value.

Abstract: An antenna receives, by capacitive effect, a current of which the intensity is a function of the distance separating the antenna from an electrical power line. The other factors that influence the current are fixed, constant or are considered negligible. A measuring and conditioning circuit converts the current at the output of the antenna into a coded signal and transmits this coded signal to a control unit. The control unit compares the coded signal to predetermined values stored therein. Alarms are generated by the control unit when the current from the antenna exceeds the predetermined values.

Abstract: Apparatus and method for monitoring a self-regulating heater comprising a PTC conductive polymer while it is being powered by a power supply signal. The apparatus is connected to a power supply and to the heater, the heater then producing a heater signal which is fed to a comparator. The comparator deterines the phasal relationship between the power supply signal and the heater signal and indicates when the signals are out of phase by a predetermined magnitude.

Abstract: A reduced power consumption low battery indicator comprising in the preferred embodiment a transducer driver which drives a transducer to provide an audible alert. A microprocessor is used to generate a squarewave signal to power the transducer driver whenever the battery is depleted to a first predetermined level. A first low battery sensor is used to determine when the battery is depleted to the first predetermined level and generates a signal which is directed to the microprocessor to commence generation of the signal to drive the transducer driver. A second low battery sensor is used to determine when the battery is depleted to a second predetermined level and generates an output signal which is directed to the transducer driver which then drives the transducer at a lower power consumption rate.

Abstract: An electric element breakdown detector includes an electric element (5: 5a: 106: 132: 172) connected in series with a switching element (6: 6a: 116: 116a: 171) which define a series connection. A processing circuit (40: 110: 174) produces a control signal to the switching element to control on and off operation of the switching element, so as to control the current flow through the series connection. A comparator (10: 119) is provided for comparing a voltage at one end of the electric element with a reference voltage produced from a reference voltage producer (12: 121, 123), and generates a result signal representing the result of the comparison. The result signal is fed to the processing circuit. The processing circuit detects the condition of the series connection by the detection of combination of the control signal and the result signal.

Abstract: Two parallel chains of resistances of like value are coupled between a pair of terminals to which a test voltage is applied. One chain is formed by connecting each cable conductor between a different pair of resistances in alternating serial fashion. A plurality of comparators each compare the potentials at nodes between pairs of corresponding resistances in each chain. The outputs of the comparators are coupled to a NAND gate for giving a fault indication when the output of one or more comparators changes state in response to one or more sensed faults.

Abstract: An environmental abnormality detecting apparatus for detecting abnormality in atmosphere such as heat, smoke, and a gas. A sampling circuit is provided for periodically sampling analog signals from a detector for detecting these phenomena. A quantizer quantizes sampled signals with step levels. An accumulator having a plurality of counters provides different accumulation times corresponding to the step levels. Reliability in accumulation effect is not degraded, and an abnormality signal can be detected in a short period of time when a degree of abnormality is high.

Abstract: A hand held voltage sensor in which a low impedance test lamp mode or a high impedance voltage test mode is selectable via a thumb accessed slide switch. In the high impedance mode, three light emitting elements provide indication of the value of voltage potential between a probe conductor and an associated ground conductor being above, below or pulsing above an adjustable threshold level.