Abstract: A bus terminal is isolated from ground potential during normal operation of the vehicle. A first current is applied to the bus terminal. A current level detector is arranged to detect a first level of the first current, or a corresponding observed voltage level, that exists or flows from the bus terminal to ground. A compensator is configured to compensate for a range in the detected first level by applying a corresponding compensating voltage level to a first resistor coupled to the current level detector. An electronic data processor is capable of estimating a first isolation level between the bus terminal and ground based on the detected first level.

Abstract: A first amplifier is arranged to receive a first signal from a first bus terminal. A second amplifier is configured to receive a second signal from a second bus terminal. An inverter input of an inverter is coupled to the output of the first amplifier. An input or inputs of an analog-to-digital converter are coupled to an inverter output of the inverter and the output of the second amplifier. The analog-to-digital converter is capable of producing a digital signal representative of the signals received from the first bus terminal and the second bus terminal. A data processor is capable of receiving an output of the analog-to-digital converter. The data processor is configured to apply one or more frequency domain transforms to the digital signal. The data processor identifies a circuit location of the ground fault or degraded isolation, a type of ground fault, or both based on the application of the frequency domain transform.

Abstract: A bus terminal is isolated from ground potential during normal operation of the vehicle. A first current is applied to the bus terminal. A current level detector is arranged to detect a first level of the first current, or a corresponding observed voltage level, that exists or flows from the bus terminal to ground. A compensator is configured to compensate for a range in the detected first level by applying a corresponding compensating voltage level to a first resistor coupled to the current level detector. An electronic data processor is capable of estimating a first isolation level between the bus terminal and ground based on the detected first level.

Abstract: A first amplifier is arranged to receive a first signal from a first bus terminal. A second amplifier is configured to receive a second signal from a second bus terminal. An inverter input of an inverter is coupled to the output of the first amplifier. An input or inputs of an analog-to-digital converter are coupled to an inverter output of the inverter and the output of the second amplifier. The analog-to-digital converter is capable of producing a digital signal representative of the signals received from the first bus terminal and the second bus terminal. A data processor is capable of receiving an output of the analog-to-digital converter. The data processor is configured to apply one or more frequency domain transforms to the digital signal. The data processor identifies a circuit location of the ground fault or degraded isolation, a type of ground fault, or both based on the application of the frequency domain transform.