Abstract: An electrical system contains two current-fed components having respective grounded housings. Each of these components is connected via a respective conductor to a common ground point. A signal-transmitting connection galvanically connects the housings two components to each other. A parasitic-current indicator is permanently installed in the system and detects parasitic currents (I.sub.S) flowing between the grounded housings and generates a warning at a predetermined signal level.

Abstract: A portable ground fault detector for use on tanker trucks to provide visual and audible warning of unsafe conditions. Closing of a grounding circuit operating at low voltage permits energizing of a circuit to show safe grounding conditions and interruption of continuity of the grounding circuit provides visual and audible warning of unsafe conditions.

Abstract: A safety harness for use with an electrostatic spray paint gun is disclosed which fits over the feed tube and the barrel of a standard electrostatic spray gun and acts both to protect the hand of the spray gun operator from an electrostatic discharge and to provide an indication of the electrostatic operation of the spray gun. A T-shaped safety shield made of non-conductive material is placed over the portions of the spray gun which may develop an electrostatic charge thereon, and is held onto the spray gun by mating strips of material. Located on the inner surface of the safety shield is a thin sheet of conductive foil which acts to channel the discharge through a wire to illuminate an indicator light located remote from the spray gun in a highly visible position.

Abstract: A ground circuit monitor (10) is disclosed for continuously monitoring the potential of a grounding brush (12) in the grounding circuit (14) used to ground a rotating member (16) within a machine (18). A proximitor (26) generates a radio frequency signal impressed across the secondary of a coupling transformer (30). The primary of the coupling transformer (30) is in series between the grounding brush and ground. In normal operation, the capacitance of the film of lubrication between the rotating member and machine prevents oscillation in the transformer. Failure of the grounding circuit increases oscillation, generating an output from the proximitor to the relay unit (32) to generate an alarm.

Abstract: A loss of neutral or ground protection circuit is disclosed which uses a simple capacitive circuit which discharges through the neutral or ground leads in normal conditions, and in the event of loss of neutral or ground charges sufficiently to trip a circuit breaker. The protection circuit may include other circuits such as ground fault detection circuits and may be in a one or three phase system. By virtue of the fact that a capacitive circuit is used to trip the circuit breaker, an inherent time delay is involved and thus the circuit breaker will not be tripped as a result of a momentary loss of neutral or ground. This is particularly important where continuity of operation of a load is important.

Abstract: The invention comprises a self-proving vehicle grounding system for placing the ground of a transportation vehicle at the same voltage as the ground of a loading rack and is intended for use in conjunction with an overfill protection system. The overfill protection system comprises a sensor unit on the vehicle and a base unit on the rack for disabling the loading equipment when the sensor detects overfill. The invention comprises three parts, a controller unit coupled to the filling station ground, a grounding bolt unit which is coupled to the transportation vehicle and a multi-conductor cable. The controller unit comprises a signal generator which produces a first electrical signal and a signal detector which, when it receives a specified second electrical signal at its input, enables the pumping equipment of the filling station.

Abstract: A method and apparatus for determining the existence of an undesired connection between an electrical system and a desired single-point ground. The electrical system is first disconnected from the desired single-point ground, and is connected to the center point of a resistive divider connected to an isolated voltage source. The voltage of the center point of the resistive divider is monitored and an indication is provided if the monitored voltage indicates the existence of undesired ground paths. The invention also includes elements for measuring the resistance value of a detected undesired ground path, thereby facilitating identification and removal thereof. The invention also includes a voltage clamp which is placed between the electrical system and the desired single-point ground when the electrical system is disconnected from the single-point ground.

Abstract: A cassette grounding apparatus includes a plurality of first contacts provided on a cassette casing for accommodating an object to be grounded in such a manner that the contacts are exposed. Each of the first contacts is electrically connected to the object accommodated in the cassette casing. A second contact which is constituted by a spring member is provided on a cassette holder into which the cassette casing is loaded. The second contact is grounded and adapted to contact one of the first contacts on the cassette casing when it is loaded in the cassette holder, thereby grounding the object accommodated in the cassette casing. A third contact which is constituted by a spring member is further provided on the cassette holder. The third contact is connected to means for detecting a contact condition between the first and second contacts, and adapted to contact the other of the first contacts on the cassette casing when it is loaded in the cassette holder.

Abstract: In a steam turbine-generator system wherein the turbine shaft is subject to an electrostatic charge buildup, an active grounding system continuously maintains the shaft at substantially ground potential. A feedback circuit is connected between two brushes contacting the rotating shaft and is operable to generate a current of a magnitude to prevent electrostatic discharge as a function of the voltage as sensed by one of the brushes. A current sensor monitors the current supplied by the feedback circuit to the shaft and the output of the current sensor is utilized to diagnose various operating conditions of the steam turbine-generator system.

Abstract: Grounding of poles in a power distribution system is checked by disconnection of the ground wire from the buried grounding conductor (rod) and measurement of the reference ground by conventional techniques. If necessary the grounding conductor is enlarged to lower ground resistance to an acceptable level between 5 and 10 ohms. A pulse generator is then connected between the grounding conductor and the ground lead at the reference pole to generate and transmit through the system netural wire a pulse, preferably on the order of 5 kHz to simulate lightning strikes on the systme neutral. Adjacent poles are then checked one at a time using a current type pickup with peak detector equipment. It is necessary to disconnect the ground wire from the ground connector. A first value is obtained by checking the effects of a pulse in the neutral wire of the distribution system adjacent the selected pole and the output is adjusted by a potentiometer to read 100.

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: Electrical monitoring circuitry simultaneously and continuously tests a three-wire ground-type AC outlet for proper line voltage, polarity of the wiring and external ground resistance. The circuitry includes a single indicating lamp, preferably a light-emitting diode, which illuminates only when the proper conditions tested for exist at the outlet. For optimum convenience, the circuitry is incorporated in a male/female outlet adaptor which, in use, is plugged into the wall outlet to be tested, thereby to establish via the phase, neutral and ground prongs of the adaptor the necessary test connections of the circuitry to the wall outlet. The adaptor includes one or more jack receptacles internally connected to the adaptor ground prong for receiving static charges from external equipment and draining same to the building ground when the light-emitting diode illuminates.

Abstract: A personnel antistatic test device includes a conductive shoe plate adapted to be stood upon by the person to be checked, a jack for receiving the plug of a wrist strap worn by the person to be checked, and circuitry for measuring effectiveness of static discharge paths through the wrist strap and through the person's footwear. Electrical circuitry is provided for measuring resistance from a touch plate, through the person's body, through the wrist strap and its lead wire. In the footwear checking mode, resistance is measured from the touch pad through the person's body, through the stockings and shoes to the shoe plate. Appropriate resistance range values are provided for the wrist strap and shoe check mode, and indicator lights are activated showing a satisfactory static discharge path, a hazard condition due to low resistance, or an unacceptable static discharge path due to high resistance.

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: An earth testing means for monitoring the status of the earth return system of an electric fence network is arranged to indicate the potential difference between the earth return system of the electric fence and a secure earth. In one embodiment the earth testing means comprises an indicator to provide a quantitive display of the fence earth-secure earth potential difference.

Abstract: A system in which an electrically conductive boring device is caused to move through the ground to provide an underground tunnel, to install underground utilities, or for any other reason. A technique for detecting if the boring device electrically engages an underground source of high voltage such as an existing underground utility line. This arrangement, is also suitable for detecting if other electrically conductive apparatus, structural member, or like means engages a similar underground source of high voltage includes means defining an electrically conductive path leading from the boring device or other such member to a grounding point sufficient to reduce to a negligible level any high voltage to which the device or like member may be subjected. The present technique monitors the current through the grounding path and indicates if the current level through the path reaches a predetermined threshold level which is selected to correspond with the presence of high voltage.

Abstract: A sensor circuit for detecting a ground fault in devices that eliminate or prevent static electricity and for producing appropriate alarm signals to indicate an undesirable ungrounded condition. In particular, the sensor circuit includes means for monitoring a ground-fault system by using a wrist strap monitoring circuit, a proximity monitoring circuit and at least one surface monitoring circuit. The wrist strap monitoring circuit and the surface monitoring circuits are used to detect the status of a grounding connection between an operator and/or a surface at a work station and a ground potential. The proximity monitoring circuit is used to determine whether an operator (or another person) is in proximity to the work station. A logic circuit means detects the status of the aforementioned monitoring circuits and selectively activates an alarm means if a fault condition exists.

Abstract: A control system for diverting/equalizing electrical potentials between two objects, for example the shell (1) of a storage tank installation and the body (10) of a tank truck/vessel, when loading flammable/explosive fluids, wherein an electrical equalizer connection (5,6,14) connects the body (10) of the tank truck via a terminal (10a) to the storage tank (1) via a terminal (1a). The terminals (1a and 10a) are part of respective control circuits comprising a low voltage source (U.sub.1 ; U.sub.2), a resistor (4; 13) and an indicator (8,9) for registering current flow and thereby controlling/blocking the connection/disconnection of a fluid pump. To check that electrical connection has in fact been established at the terminals (1a,10a), each of these is connected to a respective control circuit via separate terminals, namely a terminal (1b; 10b) on the respective bodies (1; 10) and a terminal (6a; 6b) on a busbar (6) in the equalizer connection ( 5,6,14).

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 fail-safe electrical ground indicator is described which includes apparatus for testing whether a vessel or piece or equipment is adequately grounded. The indicator further includes grounded parallel resistors for checking the integrity of the test apparatus, means for making electrical contact between the test apparatus and each of the resistors one at a time, means for making electrical contact between the test apparatus and both resistors at the same time, means for determining whether an electrical current passing through the test apparatus and each of the resistors separately exceeds a specified value, and means for determining whether an electrical current passing through the test apparatus and all of the resistors exceeds the specified value.

Abstract: Apparatus which can be embodied in an electronic wristwatch monitors the integrity of a wrist strap ground. An input terminal to which a known ground is coupled is provided. An oscillator produces a fixed frequency which is mixed with a signal from the input terminal to provide a composite signal. The composite signal is coupled to one input of an exclusive OR-gate. The other input of the exclusive OR-gate is coupled directly to the output of the oscillator. The output of the OR-gate is processed to produce an output signal indicative of the phase relationship between the oscillator output and the composite signal. When the input terminal is grounded, the phase relationship between the oscillator output and the composite signal changes, resulting in a change in the output signal which can be used to trigger an indicator (e.g., visual display and/or aural alarm) to indicate to a user whether he or she is properly grounded.

Abstract: A ground continuity monitor for a tool stop controller includes a pair of resistive conductors connected in series between the power line hot and neutral leads. At the junction therebetween they are connected to the ground lead and to a controllable shunt. The resistive conductors maintain a sufficient voltage at the junction to hold the shunt in a conducting state until the junction is connected to ground through a low impedance, preferably less than substantially 100 ohms. An indicator, such as a lamp, indicates the state of conduction of the shunt, thereby providing the tool operator with an indication of the actual electrical continuity of the ground path from the tool ground lead back to ground at the power line source. In the event of a ground fault, no high voltage is imposed by the monitor on the tool case.

Abstract: A monitor for sensing any break in electrical continuity between a body and earth when the body is coupled to earth by way of a grounding tether used to prevent build-up of static charges on such body. The monitor includes an oscillator circuit for generating A.C. output voltages which are adapted to actuate an alarm. Body capacitance and resistance are coupled by way of the tether across an impedance network either in the tuned circuit determining oscillator frequency or in the output load thereof whereby the resistance or inductance of the impedance network provides the path to ground for the body through its tether. With body capacitance and resistance components of the total impedance, variable elements in the impedance network are adjusted to diminish the circuit output voltage below the threshold voltage required to actuate the alarm when continuity exists while developing an output voltage level sufficient to actuate the alarm when a break in continuity occurs.

Abstract: A bi-directional system for ensuring that a ground connection is made in a three-wire conductor system including a line "hot" conductor, a line neutral conductor, and a ground conductor includes a circuit for generating direct current potential related to the potential difference between the line "hot" conductor and ground and a second circuit for generating a direct current potential related to the potential difference between the line "hot" conductor and ground. A circuit including a male plug for insertion into a female receptacle includes a first prong for coupling alternatively to the line "hot" conductor or the line neutral conductor, a second prong for coupling alternatively to the line "hot" conductor or the line neutral conductor, and a third prong for coupling to the line ground conductor.

Abstract: Disclosed is a ground conductor monitoring system which makes efficient use of an audio signal to continuously check the continuity of at least the ground conductor of a cable system.

Abstract: A safety circuit prevents shocks, and is particularly useful with a television camera head and processing unit that are connected by a triaxial cable. The circuit applies power to the triax at the processing unit. If the current is interrupted, the power is no longer applied and a selected impedance is applied to the triax at the camera. If said impedance can be detected at the processing unit, power is reapplied to the triax. The impedance can comprise a diode, which has different effects upon different alternating signal polarities.

Abstract: A power line fault detector (10) includes a capacitive impedance (12) and another impedance (14) connected in series between the hot and ground conductors of the power line, with a trigger circuit (16) being connected between the neutral conductor of the power line and the junction of the impedances. The impedances have values selected such that the voltage at the junction thereof with respect to the neutral conductor does not exceed a preselected limit unless the power line is faultily connected. The trigger circuit normally has a high impedance but switches to a low impedance when the voltage across it exceeds the preselected limit, then producing a surge of capacitive impedance charging current. A sensing circuit (20, 21, 26) senses the surges of current in the trigger circuit and provides an indication to the operator that the power line is faulted.

Abstract: A ground detecting device for a vehicle, craft, or the like, having a storage tank mounted on the vehicle, or the like, equipment for selectively controlling the pumping of fluid into and out of the storage tank, comprises a transformer having first, second and third windings, the third winding being electrically connected to ground. A jack is electrically connected in shunt with the third winding. A prong is electrically connected to the vehicle, craft, or the like, and cooperates with the jack, when inserted therein, to short-circuit the third winding to ground. The short-circuit has a short-circuit impedance resulting in a voltage differential at the second winding. A comparator amplifier has a sensing input electrically connected to the second winding, a reference input, and an output. An astable multivibrator has an output electrically connected to the reference input of the comparator amplifier and to the first winding and supplies a reference input signal thereto.

Abstract: When explosive fuels such as hydrocarbons are pumped into or out of a barge or tanker, a metallic conduit having an insulated flange therein is typically connected to the barge. The method of this invention involves connecting the barge to the earth through a barge-grounding cable, connecting the metallic conduit to the earth through a conduit-grounding cable, whereby a grounding test circuit is established with a current source connected between the earth and the grounding cables. A flange resistor is connected across the insulated flane to form a flange circuit. The currents flowing through the grounding cables are being continuously monitored in the grounding circuit to determine the presence of a broken connection or of an ineffective electric contact. A continuity test is also continuously being made of the flange insulation in the flange.

Abstract: A method for continuously measuring and monitoring insulation resistance values of a non-grounded DC circuit in an operative condition and an apparatus for practicing the method are disclosed. This method is to calculate various values including the values of the insulation resistances across three lines forming the non-grounded DC circuit by continuously measuring only two voltages across the three lines forming that circuit. The apparatus includes voltage detecting means, switching means, memory means, and calculating means. A load resistance is connected to each of the positive power line and the negative power line, and the switching means operates to selectively ground these load resistances. The voltage detecting means further includes a buffer circuit. The memory means temporarily stores the detected voltage value. The calculating means is connected to the memory means for calculating various values including the insulation resistance values utilizing the voltage values.

Abstract: By introducing a secondary voltage having a lower frequency than the principal voltage in a grounded transmission line system, detecting the current arising from such secondary voltage only and multiplying such current by the magnitude of the secondary voltage a resultant signal is obtained which is proportional to the inverse of the insulation resistance of the system.

Abstract: A system for monitoring the continuity of at least the ground wire of a cable connected between a mining machine and a power center. At the power center, a monitor signal is coupled to multi-phase power conductors of the cable through a multi-phase filter. The monitor signal from the conductors is coupled to the ground wire at the mining machine through another multi-phase filter. The signal returns through the ground wire to the power center where a current transformer couples the signal from the ground wire to a receiver. The receiver which receives and senses the characteristics of the returned signal includes parallel phase locked loop discriminators to prevent false tripping of the main power breaker if the monitor frequency should vary only slightly. The parallel discriminators provide a fail safe arrangement to prevent the main power breaker from remaining closed if one of the parallel discriminators should malfunction.

Abstract: Apparatus for on-site testing of wrist straps or shoe straps of the type d to prevent the buildup of electrostatic charges on the body and clothing of a worker engaged in handling charge-sensitive electronic devices. The worker wearing a grounding strap connects the grounding strap to a terminal on the tester and touches a touch pad on the apparatus. The tester incorporates the resistance of the grounding strap and the worker wearing the strap into a voltage divider. If the incorporated resistance is within acceptable limits, an indicating lamp is lighted to show that the grounding strap is working properly. An indicating signal may also be coupled to a computer for automatic recordkeeping.