A method for checking quality when resistance-welding workpiece includes pressing welding electrodes with an electrode force against a weld spot of the workpieces using an electrode drive and energizing the welding electrodes with a welding current for a duration of a welding time in order to liquefy a surface of the workpieces. The method further includes determining, at a first time before a beginning of the liquefaction, a first value of a welding electrode parameter identifying a position of one or both electrodes, and determining, at a second time after the beginning of the liquefaction, a second value of the welding electrode parameter identifying a position of one or both electrodes. The method further includes comparing the first value and the second value and, evaluating a quality of the welding process based on the comparison.

A method for checking quality when resistance-welding workpiece includes pressing welding electrodes with an electrode force against a weld spot of the workpieces using an electrode drive and energizing the welding electrodes with a welding current for a duration of a welding time in order to liquefy a surface of the workpieces. The method further includes determining, at a first time before a beginning of the liquefaction, a first value of a welding electrode parameter identifying a position of one or both electrodes, and determining, at a second time after the beginning of the liquefaction, a second value of the welding electrode parameter identifying a position of one or both electrodes. The method further includes comparing the first value and the second value and, evaluating a quality of the welding process based on the comparison.

An impedance sensing circuit includes first and second current sources and first and second bias current sources that are appropriately coupled to first and second resistors. The impedance sensing circuit also includes a comparator that compares a first voltage based on the first terminal of the first resistor to a second voltage based on the first terminal of the second resistor to generate a comparator output signal. Either the comparator output signal or a digital signal based on the comparator output signal operates to regulate the current signals output from the first and second current sources so that the first voltage is same as the second voltage. The comparator output signal and the digital signal is representative of a difference between the first voltage and the second voltage that is based on an impedance difference between the first resistor and the second resistor.

An impedance sensing circuit includes first and second current sources and first and second bias current sources that are appropriately coupled to first and second resistors. The impedance sensing circuit also includes a comparator that compares a first voltage based on the first terminal of the first resistor to a second voltage based on the first terminal of the second resistor to generate a comparator output signal. Either the comparator output signal or a digital signal based on the comparator output signal operates to regulate the current signals output from the first and second current sources so that the first voltage is same as the second voltage. The comparator output signal and the digital signal is representative of a difference between the first voltage and the second voltage that is based on an impedance difference between the first resistor and the second resistor.

A control system for controlling an adjustable output voltage provided to a heater includes a controller configured to determine an input parameter based on an electrical characteristic of the heater, where the heater includes a resistive heating element that is operable to emit heat and as a sensor. The controller is further configured to determine an output voltage for the heater based on the input parameter and a desired setpoint, and to transmit a signal to a power converter to generate the output voltage. The desired setpoint is based on an operational state of the heater, and the input parameter includes data indicative of a temperature of the resistive heating element that is determined based on the electrical characteristic.

A control system for controlling an adjustable output voltage provided to a heater includes a controller configured to determine an input parameter based on an electrical characteristic of the heater, where the heater includes a resistive heating element that is operable to emit heat and as a sensor. The controller is further configured to determine an output voltage for the heater based on the input parameter and a desired setpoint, and to transmit a signal to a power converter to generate the output voltage. The desired setpoint is based on an operational state of the heater, and the input parameter includes data indicative of a temperature of the resistive heating element that is determined based on the electrical characteristic.

A current sense system may include a relay, a load conductor, and an integrator sub-circuit. Current may be provided to an electrical load via the load conductor and a latch of the relay. The current carried via the load conductor may induce a sense voltage in a coil of the relay. Based on the sense voltage induced in the relay coil, the integrator sub-circuit may determine a load sense voltage that indicates a level of the current carried via the load conductor. In some implementations, a current indication module may provide an indicator signal based on the load sense voltage. In addition, the indicator signal may be provided to additional components or devices, such as a relay controller configured to activate the latch. In some implementations, the relay controller may be configured to open the latch based on the current level described by the indicator signal.

A current sense system may include a relay, a load conductor, and an integrator sub-circuit. Current may be provided to an electrical load via the load conductor and a latch of the relay. The current carried via the load conductor may induce a sense voltage in a coil of the relay. Based on the sense voltage induced in the relay coil, the integrator sub-circuit may determine a load sense voltage that indicates a level of the current carried via the load conductor. In some implementations, a current indication module may provide an indicator signal based on the load sense voltage. In addition, the indicator signal may be provided to additional components or devices, such as a relay controller configured to activate the latch. In some implementations, the relay controller may be configured to open the latch based on the current level described by the indicator signal.

The present invention provides a measurement circuit and a measurement method. In the measurement circuit, a comparison unit is configured to compare a first preset value and a second preset value to obtain a voltage difference, an accumulation and subtraction unit is configured to perform counting according to a comparison result, and a control unit is configured to adjust the voltage difference between two compared voltage input terminals, thereby calculating a voltage resolution of the control unit, avoiding the impact of the actual error of the first constant current source and the unit resistor on the actual voltage resolution, and ensuring the measurement accuracy. In addition, an accurate to-be-measured voltage is calculated, and a measurement value of the to-be-measured voltage is corrected, to ensure the high measurement accuracy of the to-be-measured voltage and the output power.

A circuit system for measuring an electrical voltage. The circuit system includes a voltage divider, an integrating element and an evaluating unit. The voltage divider receives, at an input, a first signal that represents the electrical voltage to be measured, and has a first switching element and a second switching element, and is capable of assuming a first state, in which the first switching element is conductive and the second switching element is non-conductive, and a second state in which the first switching element is non-conductive and the second switching element is conductive, and outputs a second signal at an output that is situated between the first switching element and the second switching element. The integrating element is designed to receive the second signal and to output a third signal. The evaluating unit being set up to accept and to evaluate the third signal in order to determine a value for the electrical voltage.