Abstract: A digital telemetry system can be calibrated to improve data communication. A receiver can receive a modulated signal with a predetermined sequence of transmitted symbols. A processing device can be communicatively coupled to the receiver for jointly performing carrier phase synchronization and symbol-timing recovery on the modulated signal to determine a corrective phase offset and a corrective timing offset. The receiver can be calibrated to use the corrective phase offset and the corrective timing offset for demodulating a subsequently modulated signal. In additional or alternative aspects, a demodulator can demodulate the modulated signal and determine an amount of interference introduced to the modulated signal. A transmitter can transmit data based on the amount of interference to a modem that transmitted the modulated signal for use by the modem to dynamically adjust hit allocation of the subsequently modulated signal.

Abstract: A resistivity logging tool includes a plurality of excitation electrodes, at least one return electrode, and a plurality of monitor electrodes. The resistivity logging tool also includes a controller that determines a set of independent currents to be emitted by at least some of the plurality of excitation electrodes during an excitation cycle based on at least one measured downhole parameter and at least one predetermined constraint.

Abstract: A digital excitation signal generator can be used to modulate excitation current or voltage to be injected into a subterranean formation by a downhole logging tool. The digital excitation signal generator can include a processor and a pulse-width modulator (“PWM”) device. The processor can generate a digital waveform and provide the digital waveform to the PWM device. The PWM device can convert the digital waveform into PWM pulses. The PWM device can be coupled to an interface. The interface can use the PWM pulses to modulate a voltage or current to be provided to an excitation electrode in the downhole logging tool. The digital excitation signal generator can also include a feedback module for maintaining a constant current output or constant voltage output to the excitation electrode.

Abstract: In one aspect, a resistivity logging tool for a fluid-producing formation if provided. The resistivity logging tool includes at least one transmitter device connected to at least one excitation electrode, multiple receiver devices respectively connected to monitoring electrodes, and a controller. The transmitter can inject an excitation current into the formation via the excitation electrode. Each receiver device can determine a respective voltage level induced by the excitation current. The controller can determine whether a voltage level measured by at least one receiver device is within a specified range. Based on the measured voltage level, the controller can select a global amplitude adjustment algorithm for modifying excitation currents or a localized amplitude adjustment algorithm for modifying one or more gains of one or more receiver devices. The controller can modify the excitation current or gains by executing the selected algorithm.

Abstract: An apparatus includes a housing. The housing includes a concentrator and a plurality of signal acquisition devices. Each signal acquisition device is coupled to a respective sensor. Each sensor measures an environmental parameter outside the housing. Each signal acquisition device includes an acoustic transducer. Each signal acquisition device includes a controller to accept measurements from the respective sensor, process the measurements and format them into a transmittable form, and transmit the formatted measurements via the acoustic transducer. A concentrator includes an acoustic transducer to receive acoustic transmissions from the plurality of signal acquisition devices, a processor to process the received acoustic transmissions, and a telemetry device through which the processor can transmit the processed transmissions.

Abstract: A resistivity logging system includes a plurality of excitation electrodes, at least one return electrode, and a plurality of monitor electrodes. The resistivity logging system also includes a controller that determines a level of excitation current to be emitted by at least one of the plurality of excitation electrodes during a subsequent excitation cycle based on a comparison of measured downhole parameter values corresponding to excitation current emitted in two previous excitation cycles.

Abstract: In a logging system (100), multiple receiver units (106) are synchronized over a control area network (CAN) bus (110) without use of separate differential lines. A ready for synchronization command is received over the CAN bus (110). In response to receiving the ready for synchronization command, a start synchronization interrupt is enabled. A start synchronization command is then received over the CAN bus (110). In response to receiving the start synchronization command, the start synchronization interrupt is triggered for capturing formation signals which are produced responsive to excitation signals from a transmitter unit (104).

Abstract: A method and apparatus for generating a low distortion sinusoidal signal with controllable amplitude for use with downhole tools, such as an array laterolog. In preferred embodiment, a signal-generating digital-to-analog converter is provided to produce a sinusoidal or other waveform at full scale. An amplitude-controlling digital-to-analog converter provides a voltage reference for the signal-generating digital-to-analog converter. The tandem combination of two digital-to-analog converters allows the generation of low distortion signals, even at low amplitudes. The amplitude-controlling digital-to-analog converter is provided digital codes by the downhole tool system processor. A high-speed dedicated controller provides digital codes to the signal-generating digital-to-analog converter, which relieves the system processor from the intensive task of providing signal generating codes, thereby freeing processor bandwidth for other system tasks.

Abstract: An example electronics module for a downhole tool includes a power source that provides an operating voltage and a processor communicably coupled to the power source to receive the operating voltage. A timer is communicably coupled to the power source and the processor and includes a real-time clock, a diode, and a capacitor. The real-time clock is powered by a primary power supply provided by the operating voltage and a backup power supply provided by the capacitor as charged through the diode. The real-time clock is powered by the primary power supply during normal operation and powered by the backup power supply when the primary power supply fails.

Abstract: A resistivity logging tool includes a plurality of excitation electrodes, at least one return electrode, and a plurality of monitor electrodes. The resistivity logging tool also includes a controller that determines a set of independent currents to be emitted by at least some of the plurality of excitation electrodes during an excitation cycle based on at least one measured downhole parameter and at least one predetermined constraint.

Abstract: In a logging system (100), multiple receiver units (106) are synchronized over a control area network (CAN) bus (110) without use of separate differential lines. A ready for synchronization command is received over the CAN bus (110). In response to receiving the ready for synchronization command, a start synchronization interrupt is enabled. A start synchronization command is then received over the CAN bus (110). In response to receiving the start synchronization command, the start synchronization interrupt is triggered for capturing formation signals which are produced responsive to excitation signals from a transmitter unit (104).

Abstract: In one aspect, a resistivity logging tool for a fluid-producing formation if provided. The resistivity logging tool includes at least one transmitter device connected to at least one excitation electrode, multiple receiver devices respectively connected to monitoring electrodes, and a controller. The transmitter can inject an excitation current into the formation via the excitation electrode. Each receiver device can determine a respective voltage level induced by the excitation current. The controller can determine whether a voltage level measured by at least one receiver device is within a specified range. Based on the measured voltage level, the controller can select a global amplitude adjustment algorithm for modifying excitation currents or a localized amplitude adjustment algorithm for modifying one or more gains of one or more receiver devices. The controller can modify the excitation current or gains by executing the selected algorithm.

Abstract: An apparatus includes a housing. The housing includes a concentrator and a plurality of signal acquisition devices. Each signal acquisition device is coupled to a respective sensor. Each sensor measures an environmental parameter outside the housing. Each signal acquisition device includes an acoustic transducer. Each signal acquisition device includes a controller to accept measurements from the respective sensor, process the measurements and format them into a transmittable form, and transmit the formatted measurements via the acoustic transducer. A concentrator includes an acoustic transducer to receive acoustic transmissions from the plurality of signal acquisition devices, a processor to process the received acoustic transmissions, and a telemetry device through which the processor can transmit the processed transmissions.

Abstract: A resistivity logging system includes a plurality of excitation electrodes, at least one return electrode, and a plurality of monitor electrodes. The resistivity logging system also includes a controller that determines a level of excitation current to be emitted by at least one of the plurality of excitation electrodes during a subsequent excitation cycle based on a comparison of measured downhole parameter values corresponding to excitation current emitted in two previous excitation cycles.

Abstract: Apparatus and systems, as well as methods, operate to acquire downhole data associated with a borehole casing, process a portion of the downhole data at a downhole location to provide processed data, and regulate surface motor power received at a motor downhole. The surface motor power is filtered and the processed data is transmitted to a surface location on a monoconductor that also carries the surface motor power. Additional apparatus, systems, and methods are disclosed.

Abstract: In some embodiments, apparatus and systems, as well as methods, may operate to acquire downhole data associated with a borehole casing, process a portion of the downhole data at a downhole location to provide processed data, regulate surface motor power received at a motor downhole, filter the surface motor power, and transmit the processed data to a surface location on a monoconductor that also carries the surface motor power. Additional apparatus, systems, and methods are disclosed.

Abstract: Improved communication systems and methods are disclosed. In one embodiment, a downhole communications system comprises a downhole transceiver and a surface transceiver. The surface transceiver receives a discrete multi-tone (DMT) modulated uplink signal from the downhole transceiver, and transmits a downlink signal to the downhole transceiver using a modulation method determined by the transceivers as communications are initiated. The downlink modulation methods supported by the surface transceiver may include DMT modulation and quadrature amplitude modulation (QAM). The modulation mode selection may be based on measured channel characteristics, on proposed data rates, or on other predetermined parameters. The uplink and downlink signals may be communicated over a shared transmission mode on multiconductor cable or wired pipe, and alternatively the uplink and downlink signals may be communicated over separate transmission modes.

Abstract: Improved communication systems and methods are disclosed. In one embodiment, a downhole communications system comprises a downhole transceiver and a surface transceiver. The surface transceiver receives a discrete multi-tone (DMT) modulated uplink signal from the downhole transceiver, and transmits a downlink signal to the downhole transceiver using a modulation method determined by the transceivers as communications are initiated. The downlink modulation methods supported by the surface transceiver may include DMT modulation and quadrature amplitude modulation (QAM). The modulation mode selection may be based on measured channel characteristics, on proposed data rates, or on other predetermined parameters. The uplink and downlink signals may be communicated over a shared transmission mode on multiconductor cable or wired pipe, and alternatively the uplink and downlink signals may be communicated over separate transmission modes.

Abstract: A downhole telemetry system having a surface transceiver, a cable, and a downhole transceiver. The downhole transceiver transmits a first category of data over a first set of frequency subchannels and a second category of data over a second set of frequency subchannels. The frequency subchannels of the first set preferably have lower error rate than the frequency subchannels of the second set. The first category of data may include data from a tool, data from a group of sensors within a tool, data sampled from a data stream at a pre-determined frequency, or a combination thereof. In at least some embodiments, the first and second sets of frequency subchannels are at lower frequencies than a third set of frequency subchannels allocated for downlink communications.

Abstract: A retractable leash for two animals which includes two spool assemblies (24A and 24B) for individual extension and retraction of each animal's cord. Each animal's cord is controlled by a button and locking mechanism. The cord holes (20A and 20B) where the leash cords (12A and 12B) exit are opposite of each other to minimize or prevent entanglement. If the leash cords cross, the operator need only rotate the lease handgrip (38) to uncross the cords. In one locking design, braking and locking buttons (18A, 18B, 18C, 18D and 16A, 16B, 16C, 16D) are placed on both the top and bottom of the leash handgrip (38) so that the operator may turn the leash and be immediately ready to control the forward movement of the animals. The leash may also be adapted to mount on the animal's collars as separate units which fasten together to form one walking leash.