A method and apparatus for calibrating an impedance measurement device are provided. The impedance measurement device outputs a first AC signal to a phase-locked current generator. The phase-locked current generator generates a second AC signal having a phase that is locked to a phase of the first AC signal and having an amplitude that is representative of a presented impedance having a known impedance value. The phase-locked current generator outputs the second AC signal to the impedance measurement device. The impedance measurement device performs an impedance measurement based on the second AC signal to produce a measured impedance value associated with the presented impedance. The impedance measurement device is calibrated based on the measured impedance value and the known impedance value of the presented impedance.

A method and apparatus for calibrating an impedance measurement device are provided. The impedance measurement device outputs a first AC signal to a phase-locked current generator. The phase-locked current generator generates a second AC signal having a phase that is locked to a phase of the first AC signal and having an amplitude that is representative of a presented impedance having a known impedance value. The phase-locked current generator outputs the second AC signal to the impedance measurement device. The impedance measurement device performs an impedance measurement based on the second AC signal to produce a measured impedance value associated with the presented impedance. The impedance measurement device is calibrated based on the measured impedance value and the known impedance value of the presented impedance.

A detection circuit for instantaneous voltage drop and an on-board diagnostic system. The detection circuit comprises two RC circuits, each of the RC circuits comprises a first resistor, a second resistor, and an energy storage capacitor; a first end of the first resistor is used for receiving a to-be-detected voltage, and a second end thereof is connected to a first end of the second resistor; the energy storage capacitor is connected in parallel with the second resistor; the first end of the second resistor forms an output end of the RC circuit, and the output end is connected to an input end of the comparator; an output end of the comparator is connected to the determination unit; in the two RC circuits, the resistance ratios of the second resistors to the first resistors are different, the capacitances of the energy storage capacitors are different.

A device can include analog circuits formed with a substrate, including a comparator, analog switches, and a balance current circuit. A sensor current and balance current can be applied at an input of the comparator. The sensor current, balance current or both can be modulated with a switch control signal. Digital circuits can include switch control logic that generates the switch control signal in response to an output of the comparator and a modulation clock signal. Digital signal processing circuits can generate a multi-bit digital value from a bit stream output by the comparator circuit. The multi-bit digital value can be an analog-to-digital conversion of the sensor current. Corresponding methods and systems are also disclosed.

A communication system that utilizes a light strip to carry data using the power and ground connections of the light strip. When used in the context of a truck and trailer, the system may include a sensor node configured to obtain status information about trailer components, and a data hub for collecting the information. The data about the trailer components may be transferred from the sensor node to the data hub using the power and/or ground connections of the light strip. The sensor node may communicate using the light strip by changing the current level of the light strip power connection, and these changes in the current level may be used by the data hub as a signal by which the data may be received.

The invention concerns a device (1) for measuring at least one parameter of a motor vehicle, the device (1) comprising at least one reference resistor (R.sub.0) of a predetermined value and at least two measuring branches (K1, K2), each of the two measuring branches comprising at least a first element comprising a resistor (R.sub.0) or a resistive sensor (R.sub.2), capable of being connected to a voltage supply (Vcc), and a second element comprising a resistor or a resistive sensor (R.sub.1, R.sub.3) capable of being connected to earth (M), the first element and the second element being connected together at a mid-point (A, B), the mid-points (A, B) of the at least two measuring branches (K1, K2) being connected together in pairs by a third element comprising a resistor or a resistive sensor (R.sub.4).

The invention concerns a device (1) for measuring at least one parameter of a motor vehicle, the device (1) comprising at least one reference resistor (R.sub.0) of a predetermined value and at least two measuring branches (K1, K2), each of the two measuring branches comprising at least a first element comprising a resistor (R.sub.0) or a resistive sensor (R.sub.2), capable of being connected to a voltage supply (Vcc), and a second element comprising a resistor or a resistive sensor (R.sub.1, R.sub.3) capable of being connected to earth (M), the first element and the second element being connected together at a mid-point (A, B), the mid-points (A, B) of the at least two measuring branches (K1, K2) being connected together in pairs by a third element comprising a resistor or a resistive sensor (R.sub.4).

Examples of operating an Intelligent Electronic Device (IED) during power swings, are described. In an example, voltage measurements for a phase is received and sampled. Root mean square (RMS) values of the voltage samples is calculated based on the voltage measurements. Delta quantities for each phase are calculated based on the RMS values. Each of the RMS values and delta quantities are associated with respective sampling instants. In response to a delta quantity being greater than a predefined threshold, a peak delta quantity is detected. A time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity is determined. Based on a comparison of the time interval with a threshold time, a disturbance condition may be detected as a power swing and consequently, fault detection at the IED may be blocked.

Examples of operating an Intelligent Electronic Device (IED) during power swings, are described. In an example, voltage measurements for a phase is received and sampled. Root mean square (RMS) values of the voltage samples is calculated based on the voltage measurements. Delta quantities for each phase are calculated based on the RMS values. Each of the RMS values and delta quantities are associated with respective sampling instants. In response to a delta quantity being greater than a predefined threshold, a peak delta quantity is detected. A time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity is determined. Based on a comparison of the time interval with a threshold time, a disturbance condition may be detected as a power swing and consequently, fault detection at the IED may be blocked.

An apparatus for smart frequency selection in a ground monitor apparatus is disclosed. The apparatus includes an energy measurement circuit that measures an energy level at a test frequency in an equipment grounding conductor between a load and a power source and an energy comparator that compares the measured energy level with an energy threshold. The apparatus includes a continuity signal circuit that injects a continuity signal with a frequency at the test frequency in the equipment grounding conductor at an energy level above the energy threshold in response to the energy comparator determining that the measured energy level is below the energy threshold. The continuity signal is an indicator for continuity of the equipment grounding conductor between the power source and load.