Abstract: The buttonless memory system of the present invention retrieves and stores the measurement results of a sample for the user of an electronic measurement device, particularly a portable and personal electrical measurement device, with minimal user interaction. The user simply activates the portable measurement device and waits as the buttonless memory system initially cycles through the stored measurement results. The buttonless memory system stops retrieving from memory when the measurement device detects a sample or control solution. After test measurement of the sample, the user can choose to store the measurement result by deactivating the measurement device during the time the memory display is on. If the sample is a control solution, the user can delete the measurement result from memory by waiting and deactivating the measurement device after the memory display is off. In this way, the buttonless memory system provides a simple and effective memory management scheme for measurement devices.

Abstract: An overcurrent trip circuit monitors the rate of rise of the current and the magnitude of the current in a power conductor and opens a circuit containing the power conductor when either the rate of rise of the current exceeds a first preselected limit value or the magnitude of the current exceeds a second preselected limit value. The inherent inductance in a metering shunt is used to produce a voltage signal that contains a component which is representative of the rate of change of current in a power conductor. This voltage signal is compared to a first reference signal to produce a trip signal when the voltage exceeds the first reference signal. In addition, the voltage signal is processed and the processed voltage signal is compared to a second reference signal to produce a second trip signal when the magnitude of the processed voltage signal exceeds the magnitude of the second reference signal. The power circuit is then opened in response to either of the first or second trip signals.

Abstract: An inverse time delay circuit includes an integrator for receiving a signal representative of a voltage or current in an external circuit and a reference signal. The integrator produces a control signal representative of the integral of the difference between the signals. A comparator compares the control signal to a second reference signal to produce an output which changes logic states when the magnitude of the control signals exceeds the magnitude of the second reference signal. A circuit is provided to control the magnitudes of one or both of the reference signals thereby providing control of the instantaneous and/or ultimate trip levels of the circuit.

Abstract: There is disclosed a novel locking device adapted for use with a length of flexible cable. The locking device comprises a body member designed to receive a flexible cable and a pivotable cable retaining member pivotally associated with one end of the body member and designed to work in conjunction with the body member to engage the flexible cable thereby allowing for the simple engagement of articles to be locked together.

Abstract: A method for modifying the frequency of a clock signal includes the steps of producing a clock signal having voltage pulses which occur at a first frequency and producing a control signal having voltage pulses which occur at a lower frequency. The frequency of the voltage pulses in the control signal is incremented in successive time intervals and the clock signal and control signal are combined such that one voltage pulse in the clock signal is deleted for each voltage pulse in the control signal. This results in a modified clock signal having a frequency which may be ramped up or down depending upon the initial frequency of the control signal and the direction in which the frequency of the control signal is incremented.

Abstract: A method of regulating the output voltage of an electric power source combines a status signal representative of the output voltage of the power source with a reference signal to produce a first control signal. A status signal representative of the output current of the power source is combined with the reference signal to produce a second control signal. A bias voltage signal is applied to a junction point and the first and second control signals are connected through an OR network to the junction point, thereby forming an output signal at the junction point. The power source output is then controlled in response to this output signal. Under normal operating conditions, the magnitude of the control signal corresponding to the power source output voltage is less than the magnitude of the bias voltage signal, and the magnitude of the control signal representative of current is greater than the magnitude of the bias voltage signal, such that the voltage sensing loop is in control of the power source output.

Abstract: Method and apparatus for converting tube waves into body waves downhole for seismic exploration are disclosed, comprising a rotary valve tube wave source for producing swept frequency tube waves that are injected into a tubing or wellbore. The tube waves are converted to body waves by an elongate tube wave converter located at a selected position downhole. The tube wave converter comprises an elongate body that preferably substantially fills the wellbore or tubing and has a preferred shape in order to convert efficiently the tube waves to body waves at the selected position downhole.

Abstract: A method of regulating the output voltage of an electric generator combines a signal representative of the actual output of the generator with a reference signal to obtain a control signal proportional to the difference between the desired output and the actual output. The control signal is modified by a non-linear transfer function which is representative of the gain of the generator over an expected operating speed and load range. The exciter field current of the generator is controlled in response to the modified control signal, thereby causing the actual output to approach the desired output. Compensation for variation in generator gain is provided by a non-linear element, inserted in the voltage control loop such that the total loop gain is substantially constant over the operating speed and load range of the generator.

Abstract: A voltage-sensing circuit producing a voltage-indicating signal representative of the voltages in a three-phase AC system produces several voltage-indicating signals which are representative of the phase voltages in a three-phase AC system. These voltage-indicating signals are squared, and the squared voltages are summed to produce an output signal having a DC voltage component with a magnitude proportional to the Mean Square value of the AC phase voltages. Unbalanced voltages in the three-phase system can be monitored by detecting the peak value of a ripple voltage imposed on the DC voltage component of the output of the circuit.

Abstract: A current limited DC power controller is provided with an output stage having a controllable solid state switching device for conducting current between a pair of output terminals and a drive circuit for controlling the operation of this switching device in response to a control signal. A programmable current source is used to produce a reference current signal in response to a command signal and this reference current signal passes through a resistor to produce a reference voltage signal having a magnitude proportional to the command signal. When the power controller is off, the reference voltage signal is clamped to a preselected value. A second voltage signal proportional to the load current is combined with the referenced voltage signal and used to produce the control signal to which the drive circuit responds.

Abstract: This invention controls the operation of solid state swithing devices in an output stage of an electronic inverter by using a counter to maintain a fixed delay between transition points in a switching command signal and a modified switch operation signal. The counter begins counting clock pulses following a transition in the switch command signal and produces a transition point in a switch drive signal when it reaches a predetermined count. The solid state switching device changes conduction states in response to the transition points in the switch drive signal. This produces a transition point in a switch operation signal. Those transition points are time-shifted by an amount corresponding to the level of DC voltage in the inverter output to produce the modified switch operation signal. The counter stops counting in response to one of the transition points in that modified switch operation signal.

Abstract: An electric generating system having a discharge circuit for a DC filter capacitor includes an electric power source for producing a DC voltage on a pair of conductors and a DC filter capacitor electrically connected between the conductors. A voltage indicating signal, representative of the actual output voltage of the generator, is combined with a reference signal to obtain a control signal which varies in proportion to the difference between the desired output voltage of the power source and the actual output voltage. Power source output voltage is controlled in response to the control signal. A branch circuit with a solid state switching device is connected across the DC filter capacitor. The solid state switching device is turned on for a limited time in response to a change in the magnitude of the control signal resulting from an increase in the actual output voltage of the power source, thereby discharging the DC filter capacitor.

Abstract: A generator voltage regulator circuit is provided with a switching circuit for alternatively connecting or disconnecting a generator exciter field winding to a DC power source. A discharge circuit is provided for conducting current, produced by a collapsing magnetic field in the exciter winding following disconnection of the winding by the switching circuit, in a revese direction through the DC power source. A driving circuit controls the switching circuit with a series of turn-on pulses. Each of the turn-on pulses is initiated in response to a transition in a clock signal and is terminated alternatively when the current in the exciter field winding reaches a predetermined magnitude or when a second transition occurs in the clock signal. This invention also encompasses a method of regulating exciter field current performed by this circuit.

Abstract: A single phase rectifier circuit produces a full wave rectified voltage by rectifying an AC input voltage, couples the rectified voltage to a filter capacitor through an inductor, and repeatedly switches the sum of the rectified voltage and the voltage on the capacitor across the inductor, thereby reducing input current distortion and improving the power factor of the circuit. When the rectified voltage is of a sufficient magnitude to drive current through the inductor, switching of the capacitor voltage across the inductor can be eliminated. The switching function is performed by a half bridge boost converter.

Abstract: A position detector is provided with an encoded element having indicia representative of a bit pattern of a pair of bits of a Gray code and a pair of sensors responsive to this indicia. The encoded element is capable of being mechanically coupled to a movable member and the sensors are spaced apart by a distance corresponding to a shift in the bit pattern between two bits of the Gray code such that movement of the encoded element past the sensors is used to produce two bits of the Gray code. Additional encoded elements and sensors are used to produce additional bits of the Gray code.

Abstract: A solid state power controller is provided with an output circuit having a transistor which is connected between a pair of output terminals. Base current to the transistor is provided by a drive circuit which includes a pair of series connected diodes that provide biasing to offset the drive circuit and output transistor base voltage drops. Load current is sensed and a DC bias current is supplied to the diode pair, with the DC bias current being proportional to the load current. For bi-directional operation, a second output transistor is connected in series with the first output transistor and a pair of reverse series connected diode are connected in a circuit branch which parallels the two output transistors. Junction points between the output transistors and the reverse series connected diode circuit branch are connected together to provide for bidirectional load current flow.

Abstract: A bi-directional DC power controller is provided with a bi-directional DC switch connected between a pair of terminals for connection to a pair of line power conductors. A first difference amplifier is connected to receive voltages at these terminals and to produce an output voltage signal which is proportional to the difference in voltages between these terminals when the voltage at one of the terminals is greater than the voltage at the other terminal, and is constant when the voltage at the second terminal is greater than the voltage at the first terminal. A second differential amplifier also receives voltage signals from these terminals and produces an output voltage signal which is proportional to the difference in voltages between the terminals when the voltage at the second terminal is greater than the voltage at the first terminal, and which is constant when the voltage at the first terminal is greater than the voltage at the second terminal.

Abstract: Rectifiers mounted on the rotor of a brushless alternator are tested by applying an AC voltage to an exciter field winding of the brushless alternator. This applied voltage induces current in a rotor mounted exciter armature winding which is inductively coupled to the exciter field winding and produces current flow through the rectifiers. The magnitude of an even harmonic component of the exciter field winding current is measured and compared to a predetermined magnitude to obtain an indication of the operational status of at least one of the rectifiers. This comparison may be done manually or may be performed electronically in accordance with known techniques.

Abstract: Voltage regulation of a DC electrical power source having a generator with an exciter field coil for producing an AC output voltage which is rectified to produce a DC output voltage, is accomplished by producing voltage signals proportional to the AC output voltage of the generator and the current in the generator exciter field winding, and combining these signals to produce a control signal. An additional voltage signal proportional to the DC output voltage of the power source is compared to a DC reference voltage signal to produce a trim error voltage signal. The trim error voltage signal is combined with an AC reference signal to produce an additional control signal. These control signals are compared and the result of that comparison is used to control the current in the generator exciter field winding.

Abstract: A system for effecting parallel operation of a pair of AC power sources includes a monitoring circuit for monitoring the difference voltage occurring between output voltages on corresponding phases of the power sources. A capacitor is connected to a charging circuit and to an output of the monitoring circuit. When the difference voltage occurring between the output voltages on corresponding phases of the power sources exceeds a predetermined threshold level, the capacitor is shorted. Paralleling of the power sources is inhibited when the capacitor voltage is below a second predetermined threshold level.