Abstract: A probe comprising an electrically conductive polymer and a pair of electrodes is placed to be contacted by the chemical. Contact changes the molecular structure or arrangement and changes the resistivity of the polymer, which is measured to actuate an indicator and/or alarm. The probe may be incorporated in a float. The chemical detector may be combined with a water detector.

Abstract: Two thermistors are mounted in a fluid detection probe, one thermistor having its surface exposed to the ambient fluids, and the other encapsulated in an insulator, such as RTV, that has a thermal conductivity greater than air. The thermistors are connected in a resistance bridge circuit between ground and a positive digital circuit voltage, which circuit applies power to the thermistors, heating them. The side of the thermistors toward the positive voltage is connected to the inputs of a comparator. When air is present, the encapsulated resistor cools more than the exposed one and, therefore, the encapsulated resistors resistance is higher producing a higher voltage at its comparator input than the exposed resistor. In the presence of a liquid, the RTV insulates its thermistor from the cooling effect of the liquid, and its comparator input voltage is therefore lower than the voltage of the exposed thermistor comparator input.

Abstract: A liquid level detector comprising a voltage-divider network, including a thermistor, connected between the terminals of a battery so that the potential at the voltage-divider output varies as a function of the resistance of the thermistor. The voltage-divider output is connected to the input of a voltage-sensitive switching circuit. The voltage-sensitive switching circuit has two stable states and is either in one state or the other depending upon whether the potential at the voltage-divider output is above or below a reference level. When the potential at the voltage-divider output indicates that the thermistor is out of a good heat conductor such as a liquid, the switching circuit closes a series circuit between the battery and an LED provide a visual indication of the low liquid level condition. The thermistor is supplied by means of a constant current source to prevent destruction of the thermistor in the event of a sharp battery voltage increase.

Abstract: A photoelectric smoke detector operating on a scattered light principle. The photosensor is connected at the input of an operational amplifier, such amplifier functioning as a threshold detector, saturation pulse amplifier and fixed pulse width compensator. Another feature of the invention resides in the provision of a special RC network connected from the output of a first transistor of a flasher section or subcircuit, which provides pulse power to the light source, to the input of a second transistor in such flasher circuit. As a consequence of this arrangement, when the LED serving as the light source tends to age, with a corresponding increase in its impedance, an appropriate signal is fed back from the aforenoted output of the first transistor to the input of the second, thereby to increase the pulse width of the output signal through the LED such that it is no longer, thereby compensating for the fact that it is no longer as bright.

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: By providing a pressure responsive actuator in controlled actuating engagement with a latch mechanism in which a spring-loaded indicator is securely retained, with said indicator being movable from a non-visible, retained position to a visible, released position in response to pressure exceeding a desired level, a unique, precision constructed pressure sensor and indicator is achieved. In the preferred embodiment, the latch mechanism comprises a plurality of elongated, resilient, spring-biased locking fingers, with the locking fingers being controllably disengaged from the indicator in response to the movement of the pressure responsive actuator. In addition, the present invention is also quickly and easily manually reset, thereby further enhancing the usability of the present invention.

Abstract: A blown circuit breaker indicator utilizing an illuminating device such as a light-emitting diode for indicating whether either a thermal electrical or magnetic circuit breaker has been tripped. The indicating device is provided in a circuit parallel to the main switch of the circuit breaker and includes a reactive element such as a capacitor.

Abstract: An electrostatic system monitor and method for monitoring the operation of static control equipment such as conductive workbench and floor mats, conductive wrist straps, and the integrity of ground connections and soldering irons and to activate indicators and alarms when the static control equipment deteriorates or malfunctions by having resistances outside of predetermined values and ranges of resistance. The electrostatic system monitor also provides for the detection of unsafe voltage potentials on soldering irons, and for a surface resistance probe for measuring the surface conductivity of conductive surfaces of the static control equipment.

Abstract: A detector/annunciator circuit for monitoring the status (opened or closed) of field process switches. A two lead "End of Line Device" (ELD) is field mounted proximate the switch, and, during normal operation, detects switch status and transmits this information to panel mounted logic that decodes and annunciates the information. If the ELD's lead wires become open or short circuited, or are subjected to a ground fault, the panel mounted logic can identify the fault, diagnose its type, and annunciate such, thus aiding system troubleshooters.

Abstract: The degree of deterioration of lubricating oil used in an internal combustion engine is detected by measuring the lubricating oil dielectric constant with a pair of spaced sensor capacitor electrodes in the lubricating oil. The sensor capacitor is connected to a fixed capacitor to form a voltage divider connected across a constant frequency AC voltage source so that a developed voltage across the sensor capacitor corresponds to the lubricating oil dielectric constant. The frequency of the AC voltage is set at a value ranging from 50 KHz to 500 KHz.

Abstract: Gas sensor consisting of a housing which is divided into two compartments 3 and 4 by means of a fluid filter 2, e.g. a bed of activated charcoal. Compartment 3 has an inlet channel 5 and contains a first gas-sensitive semiconductor 6, the measuring device. Compartment 4 has an outlet channel 7 and contains a second gas sensitive semiconductor 8, being used as a reference device. The value of the electric resistances of devices 6 and 8 will increase or decrease when the compartments 3 and 4 contain either an oxidizing or a reducing gas. The sensor is used in a gas detection system in which an electronic circuit which follows determines the ratio between said resistances and the ratio of the reference device and a reference resistance. These ratios are subsequently compared to certain limiting values, and when these values are exceeded, a detection signal will be produced.

Abstract: A warning device is responsive to the failure of an electric power supply for activation to a warning mode. The warning device includes an arm pivotally mounted to a frame member and latched by an electromagnet in a non-warning mode. In the non-warning mode, a collapsible warning sign carrier is enclosed within an enclosure formed by the frame and the arm. When the supply of power is interrupted, the electromagnet releases the arm so that the arm pivots to a warning position.

Abstract: In the light-scattering type smoke detector with a disorder detecting circuit, the Munsell value of lightness of the inside surface of the dark chamber is raised to 2-4. Thereby, not only disorder of the apparatus but also performance drop of apparatus parts can be detected.

Abstract: An apparatus and method for detecting an AC power failure condition employs a fast attack, slow decay, energy storage circuit for tracking an AC input signal and for providing a slowly decaying output based upon a last received peak voltage input value. A current detection circuit monitors the current flow to the storage circuit from the AC mains and generates a current detection signal in response thereto. A power failure condition is declared when either the voltage across the energy storage circuit decays below a selected threshold value or current is not detected flowing to the energy storage circuit at a selected time. A particular current detection circuit employs a high permeability core which is saturated by a current in the sensed line having a current value below an expected peak current flowing to the energy storage circuit. An interrogation pulse periodically energizes an interrogation winding which, in the absence of current in the sensed line, induces a signal across an output winding.

Abstract: An apparatus to monitor a circuit in which an AC voltage source is connected to a plurality of paralleled current consuming loads, such as heaters, including a reactive load in parallel with the current consuming loads at a point in the circuit more distant from the voltage source than any of the current consuming loads being monitored, a phase shift detector connected to the current consuming loads and at a point in the circuit between the voltage source and the nearest current consuming load being monitored, the phase shift detector being sensitive to the shift in current phase induced by the reactor load, and an alarm connected to and actuated by the phase shift detector which provides a warning when the phase shift induced by the reactive load is lost, indicative of a failure in the circuit.

Abstract: A monitoring arrangement for a gas turbine spark ignition system in which the spark discharge current oscillates at a known frequency includes a sonic sensor accoustically coupled to the spark igniter, a filter for passing only those signals from this sensor which have a frequency corresponding to that of the discharge current and indicating means responsive to the filter output for indicating that the spark igniter is operating. An additional optical sensor may provide a signal response to a spark gap in the ignition system, signals from both sensors being required to energize the indicating means.

Abstract: A level indication has a ratio-measurement mechanism whose measurement coil can be connected to a source of current (6) via a switch element (12). This switch element (12) is controlled by the output of a comparator (10) to the input side of which a voltage signal from a transmitter (5) monitoring the level and the output of a frequency transmitter (11) are fed. Between the transmitter (5) and the comparator (10) there is arranged a damping device (8) so that the signal coming from the transmitter (5) is made stable before it arrives at the comparator (10).

Abstract: A method and arrangement of apparatus is provided for remotely and selectively determining the existence of a failed fuse in the rectifier circuit of a brushless exciter rotor. A current transformer is disposed about each fuse in such a way that uses the conductor which carries current to the fuse as the primary winding of the current transformer. A light emitting diode is connected in series with the secondary winding of the current transformer. The emitted light, indicating a current flow through the fuse, is sensed by a stationary photodetector. This method senses the existence of a current flow through the exciter fuses and thereby positively determines each fuse that has not failed. Electronic circuitry is used to synchronize the detection operation with the rotation of the brushless exciter rotor so that each fuse is inspected at a time when it is expected to be carrying its maximum current. Since this method looks for the existence of current through each fuse, it operates in a failsafe manner.

Abstract: A method and an arrangement of apparatus is provided for remotely detecting the existence of a failed fuse of a brushless exciter rotor's rotating rectifier assembly. A conducting fuse produces a magnetic field which is sensed by elements on a stationary structure. A signal corresponding to the conducting status of each fuse is synchronized to the rotational speed of the brushless exciter rotor by means of a preselected oscillator frequency and the status of each individual fuse is retained and displayed until the next inspection of that fuse. Alarm circuitry enables automatic detection of a failed fuse and shutdown in the event of multiple fuse failures. Since this method looks for the instance of current through each fuse, it operates in a fail-safe manner.

Abstract: An automated SCR cell test exercises each of the twelve SCRs in a dual, 3 phase, full wave SCR rectifier bridge singly to detect shorted SCRs and in pairs to detect open SCRs or faulty gate circuits.