Abstract: A wellbore tractor is provided. The wellbore tractor includes a single hydraulic line and at least one valve disposed along the single hydraulic line. At least two pairs of drives hydraulically coupled with the single hydraulic line such that the single hydraulic line can control the drives to open and/or close. A valve can be disposed along the single hydraulic line between each pair of drives. By controlling the opening and/or closing of each valve, along with controlling the inflow or removal of fluid in the hydraulic line, each pair of drives can be individually controlled to maneuver the wellbore tractor.

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 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: 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: 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).