A measuring circuit for determining the magnitude of a current flowing through a conductor, the measuring circuit having an input terminal pair that can be connected to the current transformer with a first switch, which connects a measuring resistor between the input terminals in a current measuring position, and which, in a voltage measuring position, separates the measuring resistor from at least one of the input terminals, and having an output terminal pair, at which, alternatively, a voltage-dependent measuring voltage present at the input terminal pair or a current-dependent measuring voltage present at a first measuring point of the measuring resistor can be tapped. The measuring circuit includes a changeover switch which can be switched synchronously with the switch. The changeover switch is used to connect an output terminal to the first measuring point in the current measuring position, and to the second measuring point in the voltage measuring position.

A current detection circuit can include: a detection power switch coupled to a power switch to be detected; a current control circuit configured to control voltages of power terminals of the detection power switch in order to generate a detection current flowing through the detection power switch when the power switch is on; and where a flowing direction of the detection current is consistent with a flowing direction of a current flowing through the power switch.

A measuring circuit for determining the magnitude of a current flowing through a conductor, the measuring circuit having an input terminal pair that can be connected to the current transformer, with a first switch, which connects a measuring resistor between the input terminals in a current measuring position, and which, in a voltage measuring position, separates the measuring resistor from at least one of the input terminals, and having an output terminal pair, at which, alternatively, a voltage-dependent measuring voltage present at the input terminal pair or a current-dependent measuring voltage present at a first measuring point of the measuring resistor can be tapped. The invention also discloses a changeover switch which can be switched synchronously with the switch. The changeover switch is used to connect an output terminal to the first measuring point in the current measuring position, and to the second measuring point in the voltage measuring position.

The present invention discloses an AC impedance measurement circuit with a calibration function, which is characterized in that only one calibration impedance is needed, associated with a switch circuit. Based on the measurement results of the two calibration modes, an equivalent impedance of the switch circuit, circuit gain and phase offset can be calculated. Based on the above results, the equivalent impedance of the internal circuit is deducted from the measurement result of the measurement mode to accurately calculate an AC conductance and a phase of the AC conductance for impedance to be measured. In addition, by adjusting a phase difference between an input sine wave signal and a sampling clock signal, impedance of the same phase and impedance of the quadrature phase can be obtained, respectively, and the AC impedance and phase angle of the impedance to be measured can be calculated.

In accordance with an embodiment, a sensor includes: a signal source with a first signal source terminal and a second signal source terminal; a bridge circuit connected to the first and second signal source terminals, the bridge circuit including: a first branch including: a first reference impedance element; and a first sensor impedance element configured to transduce a magnitude to be measured into a first impedance-related parameter; and a second branch including: a second reference impedance element; and a second sensor impedance element configured to transduce the magnitude to be measured into a second sensor impedance-related parameter.

A voltage detector comprises an input, a resistor divider circuit having resistors coupled in series with one another between the input and a reference node, and N intermediate nodes joining adjacent pairs of the resistors. The voltage detector has N switches coupled to the respective intermediate nodes, as well as a comparator with an input coupled to the switches, a state machine having an input coupled to the output of the comparator, and a decoder having N decoder outputs coupled to respective control terminals of the N switches.

The present invention discloses an AC impedance measurement circuit with a calibration function, which is characterized in that only one calibration impedance is needed, associated with a switch circuit. Based on the measurement results of the two calibration modes, an equivalent impedance of the switch circuit, circuit gain and phase offset can be calculated. Based on the above results, the equivalent impedance of the internal circuit is deducted from the measurement result of the measurement mode to accurately calculate an AC conductance and a phase of the AC conductance for impedance to be measured. In addition, by adjusting a phase difference between an input sine wave signal and a sampling clock signal, impedance of the same phase and impedance of the quadrature phase can be obtained, respectively, and the AC impedance and phase angle of the impedance to be measured can be calculated.

The present invention discloses an AC impedance measurement circuit with a calibration function, which is characterized in that only one calibration impedance is needed, associated with a switch circuit. Based on the measurement results of the two calibration modes, an equivalent impedance of the switch circuit, circuit gain and phase offset can be calculated. Based on the above results, the equivalent impedance of the internal circuit is deducted from the measurement result of the measurement mode to accurately calculate an AC conductance and a phase of the AC conductance for impedance to be measured. In addition, by adjusting a phase difference between an input sine wave signal and a sampling clock signal, impedance of the same phase and impedance of the quadrature phase can be obtained, respectively, and the AC impedance and phase angle of the impedance to be measured can be calculated.

The present invention discloses an AC impedance measurement circuit with a calibration function, which is characterized in that only one calibration impedance is needed, associated with a switch circuit. Based on the measurement results of the two calibration modes, an equivalent impedance of the switch circuit, circuit gain and phase offset can be calculated. Based on the above results, the equivalent impedance of the internal circuit is deducted from the measurement result of the measurement mode to accurately calculate an AC conductance and a phase of the AC conductance for impedance to be measured. In addition, by adjusting a phase difference between an input sine wave signal and a sampling clock signal, impedance of the same phase and impedance of the quadrature phase can be obtained, respectively, and the AC impedance and phase angle of the impedance to be measured can be calculated.

At least two redundant analog input units for a measurement current have analog inputs which are connected in parallel and upon which voltage measuring devices directly lie to convert respectively applied voltages into a digital measurement value, wherein in order to detect errors, in particular in order to detect wire breakage, each analog input unit compares its generated measurement value with a threshold and outputs an error message if a measurement value is detected that falls below the threshold, where if the analog input of the analog input unit is in the low-resistance state, then the at least one other analog input unit is additionally caused to assume a current-measuring function and switch the analog input of the analog input unit to a low-resistance state.