A method for measuring a contact resistance at an interface of an electrically conductive coating and a cross-ply surface of a composite layer having electrically conductive fibers. The method includes: placing a dielectric coating of a sensing pad in contact with the composite layer or with the electrically conductive coating on the cross-ply surface of the composite layer; electrically connecting first and second input terminals of a comparator to the sensing pad and to one side of a capacitor respectively; electrically connecting another side of the capacitor to a fixed resistance; electrically connecting the fixed resistance to an electrically conductive body inserted in a hole in the composite layer; supplying an alternating current to the electrically conductive body and to the fixed resistance; and outputting a characteristic voltage signal if an amplitude of the input signal at the first input terminal is at least equal to an amplitude of the input signal at the second input terminal.

An impedance sensing circuit includes three impedance elements and a sensing element arranged in a bridge configuration. A first input terminal is coupled to two of the impedance elements to apply a stimulus signal. In a mutual-sensing mode, a second input terminal is coupled to the third impedance element and the sensing impedance element to apply an opposite phase stimulus signal. The impedance sensing circuit may be configured in a self-sensing mode, in which the opposite phase stimulus signal is decoupled from the third impedance element and the sensing impedance element. At least one of the impedance elements is variable and may be adjusted to balance an offset impedance load on the sensing element.

An impedance sensing circuit includes three impedance elements and a sensing element arranged in a bridge configuration. A first input terminal is coupled to two of the impedance elements to apply a stimulus signal. In a mutual-sensing mode, a second input terminal is coupled to the third impedance element and the sensing impedance element to apply an opposite phase stimulus signal. The impedance sensing circuit may be configured in a self-sensing mode, in which the opposite phase stimulus signal is decoupled from the third impedance element and the sensing impedance element. At least one of the impedance elements is variable and may be adjusted to balance an offset impedance load on the sensing element.

The present disclosure relates to a sensor circuit, including a first connection, a second connection and a bridge circuit, which is connected between the first connection and the second connection, having a plurality of bridge resistors with a respective temperature coefficient. The bridge circuit has a measurement sensitivity and a temperature coefficient of measurement sensitivity and a bridge offset with a temperature coefficient of the bridge offset. The sensor circuit further includes at least one compensating resistor, which is connected between the first connection and the second connection, with a temperature coefficient that differs from the temperature coefficient of the bridge resistors.

An impedance sensing circuit includes three impedance elements and a sensing element arranged in a bridge configuration. A first input terminal is coupled to two of the impedance elements to apply a stimulus signal. In a mutual-sensing mode, a second input terminal is coupled to the third impedance element and the sensing impedance element to apply an opposite phase stimulus signal. The impedance sensing circuit may be configured in a self-sensing mode, in which the opposite phase stimulus signal is decoupled from the third impedance element and the sensing impedance element. At least one of the impedance elements is variable and may be adjusted to balance an offset impedance load on the sensing element.

A gas sensor for detecting a physical and/or chemical value of an analysis gas, a corresponding manufacturing method, and operating method. The gas sensor is based on the principle of a thermal conductivity measurement with the aid of a sensor structure including a double meander structure made up of two resistor lines, as part of a Wheatstone bridge circuit, on a diaphragm of a substrate. The two resistor lines are energized in opposite directions as a function of the detected temperature. The physical and/or chemical value(s) of the analysis gas are/is subsequently determined as a function of the voltages detected at the double meander structure.