Abstract: A system includes a heating element, a signal injector, and a signal receiver. The heating element is coupled between a first node and a second node. The signal injector is communicatively coupled the heating element via the first node. The signal generator is configured to provide a test signal to the heating element. The signal receiver is communicatively coupled to the heating element via the second node. The signal receiver is configured to receive the test signal from the heating element and to determine a capacitance of the heating element based upon the received test signal.

Abstract: The present invention discloses a relay diagnostic circuit for a number of relays connected in series between an electric vehicle power supply end and a load or a charging end. The relay diagnostic circuit includes a number of voltage divider branches connected to a same reference ground, an isolation unit and a judgment unit. Each of the voltage divider branches is configured to obtain the voltage of one end of each relay and output the voltage after dividing the voltage. The isolation unit is configured to isolate and convert a number of divider voltages output from the number of voltage divider branches and output the voltages to the judgment unit. The judgment unit is configured to compare a comparison information of divided voltages at two ends of each relay with a corresponding driving state of the relay and obtain the diagnosis result of each relay.

Abstract: A probe system includes a heater and a control circuit. The heater includes a resistive heating element routed through the probe. An operational current is provided to the resistive heating element to provide heating for the probe. The control circuit is configured to monitor the operational current over time and determine a half-life estimate of the resistive heating element based upon an exponential function of the operational current over time.

Abstract: An electric current flow indicator senses electrical current flowing through an electrical device and produces a visible feedback to indicate proper operation. The current flow indicator has a voltage and current regulation circuit having first and second inputs connected to first and second conductors, respectively. The circuit converts an AC line voltage carried by an electrical supply cord into a limited low voltage DC current. A toroidal core inductor coil and at least one current indicating LED are connected to the circuit. The first conductor passes through a center of the inductor coil. A transistor amplifier is connected to an output of the inductor coil for energizing the current indicating LED when an electrical current conducts through the first conductor. The flow indicator can be integrated into an electrical supply cord, a male or female electrical cord end, a single or duplex electrical outlet, or a universal plugin adapter.

Abstract: A cooking appliance have at least one burner operable in an ON condition for producing heat and an OFF condition for not producing heat and a Hot Surface Indicator having an illumination source that may be operated when the burner is not producing heat as well as a method for illuminating the Hot Surface Indicator.

Abstract: The present subject matter relates to methodologies and algorithms for providing anode rod depletion detection and warnings thereof to consumers. Consumers general are not concerned with monitoring consumption of protective anode rods incorporated within water heaters, The present subject matter provides automatic monitoring of anode rod depletion and provides the consumer with notification of rod depletion beyond a predetermined amount by one or more of optical, audible, or electronic devices. Aspects of the algorithm include handling of start-up conditions, service board replacement conditions, and properly defining the anode rod depletion threshold. Additional algorithm aspects include considerations for taking into consideration power outage conditions and accurately estimating galvanic current.

Abstract: An open fuse block is provided having a visual indicator or light assembly connected in parallel with a replaceable fuse mounted in the fuse block. When the fuse is blown, the corresponding visual indicator is illuminated to identify the blown fuse, thereby facilitating quick and easy replacement of the fuse. Since the visual indicator is connected in parallel with the fuse element, when the fuse is blown, the fuse results in an open circuit and the flow of electricity is rerouted through the visual indicator. The visual indicator is thereby illuminated and the corresponding blown fuse can be easily identified. The visual indicator or light assembly can include, for example, a neon bulb, light emitting diode, fluorescent bulb, incandescent bulb, or any other visual indicator that emits light.

Abstract: Systems and methods for monitoring infrared heating elements are described. The system can include a plurality of electric infrared heating elements connected to a power source and installed in a heating device and an electronic monitoring system connected to the power source and communicatively connected to each infrared heating element. The electronic monitoring system can feature a computer and an alert system for creating an alert to notify a user when one of the infrared heating elements has ceased functioning. Each infrared heating element can be labeled so that each alert generated by the alert system can be matched with the label that corresponds to the non-functioning infrared heating element about which the alert has been generated.

Abstract: A sheet switch (142) has a bottom layer (144) and a top layer (160). First and second conductors (148, 162) located on the bottom layer (144) form two separate conductive paths, with a voltage potential applied to the conductors (148, 162). The top layer (160) includes a ground conductor (172). Spacers (178) are positioned between the top and bottom layers (160, 144). When forces are externally applied, the spacers (178) collapse and the ground conductor (172) contacts the first and second conductors (148, 162), and establishes a conductive path therebetween.

Abstract: An apparatus is provided for holding articles, such as keys, which is attachable to a person's clothing, handbag or a purse, and wherein a physical or electronic tether is used to allow the user to use the articles stored thereupon without removing them from the holder or from their clothing, handbag, purse, briefcase or other hand carried item. The tension on the tether is manageable by the use of a tension management system, so that the tension of the tether will not damage the article or the mechanism that the article is used with and the article is tracked by use of the tether so that the user does not lose the article. Infrared, radio frequency, and transponder and polling versions of the invention are also disclosed.

Abstract: A method for determining a maintenance interval for a consumable part and/or for equipment containing a consumable part obtains a plurality of measurements of temperature of the consumable part, receives each of the measurements at a totalizing unit, correlates each of the measurements to one of a plurality of temperature subranges, accumulates for each of the subranges an amount of time the measurements of temperature were correlated to each of the subranges, determines a total time by aggregating the accumulated time for each subrange with a weighting function, and generates a signal to prompt a maintenance event when the total time equals or passes a runtime setpoint. In supplement to or in alternative to the above, the method also correlates a subrange of two sequential measurements, indexes a breakpoint register if the correlated subranges are different, and generates a signal to prompt a maintenance event when a value of the breakpoint register equals or passes a breakpoint setpoint.

Abstract: A heater unit includes power failure management to detect disruptions in the electrical power supply, such as the AC supply, for the unit. The heater unit emits an audible alarm in response to detection of such a disruption, and may shut down the heater(s) and visuals display(s). The heater unit advantageously includes a power storage device, such as a super-capacitor, to temporarily power the electronic circuitry of the heater unit. Operating parameters, such as of a processor of the electronic circuitry, may be stored in a non-volatile memory response to the disruption, and recalled if the disruption terminates before the level of power has gotten too low to sustain reliable operation of the processor.

Abstract: A cathodic protection device having a sacrificial anode that is intended to wear out due to corrosion and that is electrically connected to a structure to be protected against corrosion. The cathodic protection device of the present invention further includes an indication device configured to detect and indicate the wear of the sacrificial anode wirelessly, without the use of cables.

Abstract: An apparatus including a rechargeable battery pack installed in an electric vehicle, the rechargeable battery pack coupled to a power supply, the power supply operable to provide a charge voltage to perform charging operations on the battery pack, a heating element to heat a fluid to be circulated through the rechargeable battery pack, a comparator circuit to compare a battery voltage of the rechargeable battery pack to a line source voltage, the comparator circuit operable to compare the battery voltage to the line source voltage and to provide an output signal when the battery voltage is less than a line voltage offset value, and a control circuit coupled to receive the output signal of the comparator, and to couple the line source voltage to the power supply, an to bypass the heating element if the comparator is not providing the output signal.

Abstract: A generator monitoring system and method includes a plurality of sensors (12) disposed within a generator enclosure (18) to sense health conditions of a generator (10) housed within the enclosure. The sensors are interconnected to provide a single communication path (14) for allowing communication with the plurality of sensors. A monitoring device (16) outside the generator enclosure receives health condition information from each of the plurality of sensors via the single communication path. A sensor may be disposed within the generator enclosure to detect particulates emitted from a monitored portion (e.g., 52) of the generator housed within the enclosure. A sensor may be disposed proximate a bus bar connection (130) of the generator to sense a health condition of the bus bar connection and generate corresponding health condition information provided to the monitoring device.

Abstract: An externally powered temperature calibration device includes a system that provides a warning of high temperatures within the device after the device has been disconnected from the external power. The warning system includes a capacitor that provides power to a light-emitting diode (“LED”) after the calibration device has been disconnected from the external power. A temperature sensor monitors the temperature of an internal component. An output signal from the sensor is used to control a switch that connects the capacitor to one of several resistors having different resistances. The switch therefore controls the discharge rate of the capacitor based on the sensed temperature at the time the calibration device was disconnected from the external power. As a result, the period during which the capacitor powers the LED can be commensurate with the time required for the internal component to cool from its initial temperature.

Abstract: Techniques for monitoring operation of a flame ignitor are provided. In one embodiment, multiple inputs are received. The inputs are received from at least one of a first group of inputs and a second group of inputs. The first group includes a flame rod voltage, a stop signal for deactivation of the flame ignitor, a fuel supply interruption signal, and an air supply interruption signal. The second group includes a start signal for activation of the flame ignitor, and a flame proven signal indicating presence of a flame produced by the flame ignitor. If inputs from the first group are received, a cause of a failure of the flame ignitor is determined. If inputs from the second group are received, a reliability of the flame ignitor is determined.

Abstract: An embodiment of the invention is a technique to generate warning of a failure of a heating element. An operational value of at least one of operating parameters of the heating element in a heater zone of a heating unit is monitored. A remaining life value of the at least one of the operating parameters is estimated. A warning is generated if the operational value exceeds a threshold value relative to the remaining life value.

Abstract: A fused disconnect switch assembly includes a pull out fuse assembly and a switch housing assembly. The fuse assembly includes a line side conducting portion, a load side conducting portion, and a fuse element therebetween. The switch housing assembly includes a fuse receptacle for receiving the fuse, a first contact assembly coupled to the line side conducting portion of the fuse and a second contact assembly coupled to the load side conducting portion of the fuse when the fuse is inserted into the receptacle. An open fuse indication device is in communication with conducting portions of the fuse, and an alarm terminal output extends from the switch assembly housing and is in communication with the open fuse indication device. The open fuse indication device provides local fuse state indication and the alarm terminal output facilitates remote fuse state indication when coupled to external circuitry.

Abstract: An externally powered temperature calibration device includes a system that provides a warning of high temperatures within the device after the device has been disconnected from the external power. The warning system includes a capacitor that provides power to a light-emitting diode (“LED”) after the calibration device has been disconnected from the external power. A temperature sensor monitors the temperature of an internal component. An output signal from the sensor is used to control a switch that connects the capacitor to one of several resistors having different resistances. The switch therefore controls the discharge rate of the capacitor based on the sensed temperature at the time the calibration device was disconnected from the external power. As a result, the period during which the capacitor powers the LED can be commensurate with the time required for the internal component to cool from its initial temperature.

Abstract: A method and a system for protecting the power semiconductor components used in the powerstages of power electronics devices, such as frequency converters, wherein calculation modeling the degree of heating of the semiconductor junction of the power components (V11–V16) is used, wherein the degree of heating of the power components between the measurable outer surface or cooler and the internal semiconductor junction is determined on the basis of the dissipation power and a thermal network model of the component, wherein the temperature of the outer surface of the power component or the temperature of the cooler is measured, wherein the modeled temperature of the semiconductor junction is the sum of the measured temperature of the outer surface or cooler and the calculated degree of heating, and wherein, based on the modeled junction temperature, an alarm is issued or some other protective action is taken.

Abstract: A method for monitoring the condition of a heating element involving installing the heating element in a location and setting the initial composition Ci of the material as a reference baseline at an initial time Ti corresponding to said installation of the heating element. Data is then collected reflecting the subsequent composition Cs of the heating element material after a subsequent time Ts at the installed location and any change in the material composition of the heating element between Ti and Ts is monitored. An alarm is sent when the change reaches a threshold value indicating a possible failure condition. According to one embodiment, an impedance monitor is provided that calculates and compares impedance at the required levels of accuracy to determine changes in material composition. The impedance monitor, or portions thereof can be embedded within a microcontroller for increased portability and functionality.

Abstract: A method for monitoring a state of a switch is disclosed. The method includes providing a high side driver circuit in communication with a voltage source, activating the high side driver circuit at a first predefined time interval, and sourcing voltage to a resistor in communication with the high side driver circuit at the first predefined time interval. Further, the method monitors the switch at the first predefined time interval, and determines the state of the switch, and deactivates the high side drive at a second predefined time interval.

Abstract: A method for monitoring the condition of an electric current-carrying heating element involving installing the heating element in a location and setting the initial composition Ci of the material as a reference baseline at an initial time Ti corresponding to said installation of the heating element. Data is then collected reflecting the subsequent composition Cs of the heating element material after a subsequent time Ts at the installed location and any change in the material composition of the heating element between Ti and Ts is monitored. An alarm is sent when the change reaches a threshold value indicating a possible failure condition. According to one embodiment, an impedance monitor is provided that calculates and compares impedance at the required levels of accuracy to determine changes in material composition. The impedance monitor, or portions thereof may be embedded within a microcontroller for increased portability and functionality.

Abstract: An apparatus is disclosed that provides an estimate of the semiconductor junction temperature of a semiconductor device as a function of the electrical current flowing across the corresponding semiconductor junction. The apparatus includes a current sensor that samples and measures the current flowing across the semiconductor junction and provides an output signal indicative of the measured value to a current-to-temperature converter. The current-to-temperature converter estimates the temperature of the semiconductor junction using equations that include constants empirically derived for the particular device configuration including cooling and mounting methods used with it. The current-to-temperature converter provides an output temperature signal that is compared to a predetermined temperature threshold value, and in the event that the output temperature signal exceeds the predetermined temperature threshold value, an alarm signal is set.

Abstract: An electrical wiring monitoring system for sensing overheating of electrical lines which could result in electrical fires. The electrical wiring monitoring system includes a housing member having front and side walls and being adapted to be mounted to a wall structure near a fuse box; and also includes a cover member being hingedly attached to the housing member and being closeable over the front wall of the housing member; and further includes a monitor assembly including a microprocessor being disposed in the housing member, and also including a power source being connected to the microprocessor, and further including an alarm-sounding assembly being connected to the microprocessor, and also including an electrical line control/display assembly being connected to the microprocessor; and also includes wire overheating detection members being connected to the microprocessor and being attached about electrical wires of electrical lines.

Abstract: A method for monitoring the condition of a heating element involving installing the heating element in a location and setting the initial composition Ci of the material as a reference baseline at an initial time Ti corresponding to said installation of the heating element. Data is then collected reflecting the subsequent composition Cs of the heating element material after a subsequent time Ts at the installed location and any change in the material composition of the heating element between Ti and Ts is monitored. An alarm is sent when the change reaches a threshold value indicating a possible failure condition. According to one embodiment, an impedance monitor is provided that calculates and compares impedance at the required levels of accuracy to determine changes in material composition. The impedance monitor, or portions thereof can be embedded within a microcontroller for increased portability and functionality.

Abstract: A fused disconnect switch assembly includes a pull out fuse assembly and a switch housing assembly. The fuse assembly includes a line side conducting portion, a load side conducting portion, and a fuse element therebetween. The switch housing assembly includes a fuse receptacle for receiving the fuse, a first contact assembly coupled to the line side conducting portion of the fuse and a second contact assembly coupled to the load side conducting portion of the fuse when the fuse is inserted into the receptacle. An open fuse indication device is in communication with conducting portions of the fuse, and an alarm terminal output extends from the switch assembly housing and is in communication with the open fuse indication device. The open fuse indication device provides local fuse state indication and the alarm terminal output facilitates remote fuse state indication when coupled to external circuitry.

Abstract: A method for monitoring the condition of an electric current-carrying heating element involving installing the heating element in a location and setting the initial composition Ci of the material as a reference baseline at an initial time Ti corresponding to said installation of the heating element. Data is then collected reflecting the subsequent composition Cs of the heating element material after a subsequent time Ts at the installed location and any change in the material composition of the heating element between Ti and Ts is monitored. An alarm is sent when the change reaches a threshold value indicating a possible failure condition. According to one embodiment, an impedance monitor is provided that calculates and compares impedance at the required levels of accuracy to determine changes in material composition. The impedance monitor, or portions thereof may be embedded within a microcontroller for increased portability and functionality.

Abstract: An automatic shut-off and indication device for an electric heating appliance is provided which includes: a sensor (2) for sensing usage of the appliance and for providing a usage-signal (US) indicating a non-usage of the appliance; a switch (10) for off-switching a heater (12) of the appliance in response to a switching signal (SS) derived from the usage-signal (US); a sensor (4) for sensing orientation of the appliance and for providing an orientation signal (OS) for indicating different orientations of the appliance; a selector (18) for activating an indicator (22) in response to the switching signal (SS), the indicator (22) signaling the off-switching of the heater (12); and an indication timer (8) for providing a time delay between off-switching the heater (12) and activating the indicator (22), which time delay is dependent on the orientation signal (OS). The shut-off of the heater (12) is signalled to the user by the indicator (22).

Abstract: A monitoring system for use with a self-service terminal (25) having a user interface is described. The system comprises: image capture means (30) for capturing images of at least part of the user interface; image storage means (34) for storing at least one image captured by the image capture means (30); image processing means (32) for comparing the at least one stored image with a subsequently captured image of the part of the user interface so as to detect the addition of an alien device to the part of the user interface; and alarm means (38) for generating an alarm signal if the image processing means (32) detects the addition of an alien device.

Abstract: An apparatus for providing a temperature based alerting signal to a user to alert the user to the occurrence of a particular or predetermined event. The temperature based alerting device may be incorporated into jewelry, garments, or a releasable strap and includes at least one spot heating element that is maintained in substantial contact with the user's skin. Upon detected occurrence of the predetermined event, as for example an incoming telephone call or page, the user is silently alerted by a change in the temperature of the spot heating element in contact with the user's skin. Subsequent action by the user, as for example answering of the incoming call or page, causes the temperature based alerting device to reset to an initial, non-alert state.

Abstract: In many technical applications, situations often arise where it is desirable to know, in real time, if a circuit is functioning. That is, it is desirable to know if, for example, a heater element is operational or blown (open). By sensing the current flowing to the circuit, it is easy to determine if the circuit is operational. However, this only provides information while the circuit is in the process of operating. There must be some real-time connection with the request or demand for power to know if in fact the device is non-operational, or if there is simply no controller request for power. A system (and method) according to the invention includes a real-time, simultaneous current and voltage sensing and arbitration device which provides a single, point of use implementation, and allows for detection and signaling of a fault condition. A circuit breaker may be constructed to incorporate such a system.

Abstract: The present invention provides open-circuit detection for detecting an open circuit in parallel-connected thermo modules. Plural rows 10a of plural series-connected thermo modules 11a, . . . 11n are connected in parallel. A detection circuit 12 is provided for each row 10a of modules to detect a change in voltage between a power terminal 17a and an intermediate terminal 18 caused by an open circuit. Switching circuits 20 in the detection circuits 12 are connected in series to an alarm circuit 14, so that if any detection circuit 12 detects an open circuit to preclude the corresponding switching element 20 from conducting, the alarm circuit 14 is activated to cause an alarm 32 to issue an alarm.

Abstract: A monitoring system for a display unit includes phototransistors for detecting light emitted from a plurality of selectively energizable light-emitting diode (LED) segments in an energized state and for generating a voltage which is representative of the light emitted from the LED segments in the energized state. A glass filter filters ambient light from the phototransistors and passes the light emitted from the LED segments in the energized state. A comparator for each of the LED segments generates a comparison signal, with the comparison signal being representative of a comparison between a predetermined reference voltage and the voltage for each of the LED segments. A conditional power supply conditionally energizes the LED segments in response to an energizing signal. A routine of a central processing unit generates display data.

Abstract: An apparatus for monitoring the current flow through a variable load such as various lengths of heater cables. The apparatus can detect a wide range of currents so that the size of the load can vary.

Abstract: A microprocessor control (10, 24) has one or more temperature responsive thermistor sensors (20, 26, 28) used to provide temperature inputs to control operation of a temperature control system. The microprocessor control subjects the thermistor sensors to a series of diagnostic tests prior to reading the thermistor sensors, the tests including short and open circuits, shorts to ground or power and leakage paths to ground. The thermistors, along with a reference resistor (R11, R26) form an RC charge circuit with a capacitor (C6, C6'). The capacitor is charged through each thermistor and reference resistor for selected open and short tests while a watch dog timer is used to determine the time taken to charge the capacitor via a timer capture port coupled to the capacitor.

Abstract: A stove including circuitry to facilitate avoidance of fires such as may be caused by grease or another flammable substance present on the stove burner. The circuitry detects when such burner has been set above a predetermined temperature or power level for a selected duration and responsively disengages same. In presently preferred embodiments, the circuitry includes an indicator circuit operative to produce an output when the predetermined temperature or power level has been exceeded. This output initiates operation of a timer circuit which will itself produce an output after the selected duration. An appropriate switching circuit is provided to then disengage the burner as desired.

Abstract: The amount of electrical power delivered to a dialysate heater in the dialysis machine is maximized without substantially exceeding a predetermined maximum allowed power consumption for the dialysis machine. The instantaneous power consumed by the machine is measured and compared to the maximum allowed power consumption. The excess of power beyond the instantaneous power consumed up to the maximum allowed power consumption is then made available to the heater. The worst case power consumption limitations of the dialysis machine components do not adversely affect the heat available from the heater. The rate at which dialysis treatments may progress may increase or the time required for dialysis treatments may decrease.

Abstract: A display is provided for indicating changes between first and second operating conditions in an appliance such as a clothes dryer. A sensing circuit senses changes in operating conditions within the appliance. A heater is connected to the sensing circuit and is responsive to various signals produced by the sensing circuit to generate heat. An elongated thermally conductive substrate is mounted adjacent to the heater for receiving and conducting thermal energy produced by the heater. A layer of thermochromic material overlies the substrate and is capable of changing colors in response to changes in the temperature of the conductive substrate.

Abstract: A cooking appliance has a heater for cooking, and a switch which generating an operational signal. The cooking appliance automatically turns off the heater a predetermined time after a last pressed switch, i.e., automatic power off function. A caution lamp indicates that the heater will automatically be turned off a minute prior to the automatic power off function.

Abstract: A control for a clothes dryer with an induction drive motor and an electric resistance heater element. A single sense winding is threaded through sensors monitoring drive motor current and heater current, generating an output voltage each time the alternating motor or heater current passes through a zero-crossing. The control monitors the ON/OFF condition of the heater and samples the lagging phase angle of the motor current, and provides an improved system of detecting when the clothes load is dry. The control provides a clothes cool-down period with controlled moisture regain as per the user dryness selection. Numerous heater related diagnostic conditions are monitored at the start of each cycle, or, throughout each cycle, including: heater ground fault detection; 208 or 240 VAC service voltage identification; heater open/short circuit detection; open door detection; heater box thermostat cycling; and restricted air flow detection.

Abstract: An image forming apparatus equipped with a binding function includes an image forming unit for forming an image onto a sheet, a binding unit provided adjacent to the image forming unit, and a malfunction detector for detecting malfunction in the operation of the binding unit. The binding unit is provided with a binding condition display, and the image forming unit is provided with an alphanumeric character display and a device for instructing the start of an image forming operation. A detected malfunction is indicated by at least one of these displays. Upon detection of a malfunction by the malfunction detector, operation of the binding unit stops, or the entire operation of the apparatus stops.

Abstract: A current monitor includes a DC isolating amplifier circuit especially adapted for adjusting the set point of a comparator. The isolating amplifier circuit includes an operational amplifier generating a first current in response to an input voltage received by the operational amplifier. The first current is transmitted to a first optocoupler and a second optocoupler which are characterized by a first CTR and a second CTR, respectively. An output of the first optocoupler is fed back to an input of the operational amplifier while an output voltage of the second optocoupler is communicated to a set point circuit. The output voltage of the second optocoupler varies as a function of the product of the input voltage of the operational amplifier and a ratio between the first CTR and the second CTR.

Abstract: Plastic mold heater moisture detection and dry out apparatus for detecting the presence of moisture in the plastic molding heaters and for drying out the heaters. The plastic mold heater moisture detection and dry out apparatus includes a heater leakage current sensor, an analog to digital converter, a microprocessor, and a triac that are operatively connected to a heater temperature sensor and the heaters. The plastic mold heater moisture detection and dry out apparatus monitors the heater leakage current that is due to moisture or the like present in the heaters and depending upon the value of this leakage current either permits normal heater operation, dries out the heaters or shuts off power if an unsafe ground fault situation exists. In drying out the heaters a series of increasing voltages are applied to the heaters during successive loops or passes to avoid heater electrical arcing that could damage and degrade the heaters.

Abstract: An apparatus and method for testing the ignition modules of gas burners is disclosed, and functions without the requirement of a gas feed in the test program. The method involves disconnecting the ignition module from the electrical supply, and from the gas feed, and employing the apparatus of the invention to apply a test voltage to the ignition module, and to various individual components of the system such as the pilot gas valve and main gas valve which are encased in the gas valve, connecting wires, etc. In order to avoid employing gas feed in the test, a simulated gas flame signal is fed to the ignition module under test using a flame simulator device which sends an appropriate signal to the ignitor module. Hence, with the gas feed disconnected, the test method and apparatus of this invention can be used to conduct the test safely, while saving time, and providing a reliable result.

Abstract: An apparatus for performing a dual mode supervisory operation, according to whether the self limiting cable is "OFF" or "ON". When the self limiting cable is in the "OFF" mode, a solid state device compares a known resistance value of the self limiting cable over its entire length by alternately testing from each end of the cable. The values of fixed comparator resistors are set at a specified ambient temperature depending on the length of the cable. Both high resistance and low resistance samples are compared to determine whether a short or an open exists over the expected operating range. When the self limiting cable is in the "ON" mode, an AC transfer relay switches the solid state supervisory circuit to a Dummy Load. This relay simultaneously switches high voltage to the self limiting cable and a self limiting cable "ON" lamp is lit. A solid state supervisory/override relay prevents false failure signals during ON-OFF switching times.

Abstract: An improved system for the detection of underloading in an electrical heating circuit where monitoring is available in proximate and remote locations. Circuit monitoring is augmented by control devices which activate alarms in visual or audible form when circuit underloading occurs. This invention has particular application in the plastics molding industry where the control of heat levels within defined ranges must be carefully monitored to ensure process efficacy.

Abstract: A thermal printer with a fault detection circuit for detecting faults in heating elements of the printer includes a print head containing heating elements and a heating circuit for each heating element and a power supply for supplying power to the heating elements. Power is supplied to the print head either directly through one terminal of the power supply or indirectly, during a test mode, through a fault detection circuit which is also connected to the print head. The fault detection circuit includes a constant voltage source, preferably formed of series-connected diodes, through which power flows to the print head. Current passing through the constant voltage source activates a photocoupler having an output the voltage of which determines whether a current is or is not flowing into the print head. A CPU which controls overall operations in the printer monitors the photocoupler and selects either a normal printing mode or a print head test mode.

Abstract: A system, utilizing an analog pulsed signal, is for monitoring the condition of a system, by way of illustration, a multi-circuit electrically heat-traced substrate. The system senses the temperature of the substrate at the end of a heat traced circuit, converts the temperature to a pulsed signal, and drives the pulsed signal along the heat tracing to the control and distribution panel for the heat tracing in direct opposition to the AC which powers the heat tracing. A receiver converts the pulsed signal to a digital temperature read-out. Utilization of an analog pulsed signal enables the system to be used in a multi-circuit system without interference or signal mixing from adjacent circuits.