Abstract: The invention relates to a measuring circuit for measuring the capacitance of a measuring capacitor which has a first and a second measuring electrode and which is coupled to a charging capacitor, wherein the frequency of the output signal of the measuring circuit is a measure of the capacitance of the capacitor, and the measuring circuit comprises a buffer amplifier with which the point between the charging resistor and the measuring capacitor is connected to the other components of the measuring circuit. The buffer amplifier changes the high impedance level of the combination of the measuring capacitor and the charging resistor to a level at which low-pass filters can usefully be applied. Buffer amplifiers are also available with an input capacitance and input resistance such that the buffer amplifier already functions in itself as a low-pass filter. An external filter is then not necessary because the filter is already present in the buffer amplifier.

Abstract: The invention relates to a device and a method for measuring an electrical property of fluid flowing through a pipe, comprising at least a first measuring electrode and a second measuring electrode placed in spatial contact with the pipe, wherein the first measuring electrode is received in a body placed inside the inner wall of the pipe, and the first measuring electrode is separated from the inner wall of the pipe by a gap, this gap extending over at least a part of the periphery of the inner wall of the pipe. As a result of these measures the distance between the measuring electrodes is greatly reduced, so that the measurement accuracy increases considerably. The measuring circuit is preferably adapted for repeated successive measurement of the resistance value and the capacitance of the fluid.

Abstract: Measuring device for local measurement of an electrical property of the content of a container, wherein at least three electrodes are disposed adjacently of each other in height direction and electrically insulated from each other, wherein each of the electrodes can be connected to an electrical measuring circuit for measuring, via one of the electrodes and one other electrode connected to an electrical earth, the electrical property of the content of the container in the vicinity of the electrodes, and wherein the electrical measuring circuit is adapted to generate at least one electric measuring signal representing the measured electrical property, and a control unit for connecting the one electrode to the electrical measuring circuit and connecting the other electrode to an electrical earth.

Abstract: The invention relates to a device and a method for measuring an electrical property of fluid flowing through a pipe, comprising at least a first measuring electrode and a second measuring electrode placed in spatial contact with the pipe, wherein the first measuring electrode is received in a body placed inside the inner wall of the pipe, and the first measuring electrode is separated from the inner wall of the pipe by a gap, this gap extending over at least a part of the periphery of the inner wall of the pipe. As a result of these measures the distance between the measuring electrodes is greatly reduced, so that the measurement accuracy increases considerably. The measuring circuit is preferably adapted for repeated successive measurement of the resistance value and the capacitance of the fluid.

Abstract: Measuring device for local measurement of an electrical property of the content of a container, comprising at least three electrodes disposed adjacently of each other in height direction and electrically insulated from each other, wherein each of the electrodes can be connected to an electrical measuring circuit for measuring, via one of the electrodes and one other electrode connected to an electrical earth, the electrical property of the content of the container in the vicinity of the electrodes, wherein the electrical measuring circuit is adapted to generate at least one electric measuring signal representing the measured electrical property, and a control unit for connecting the one electrode to the electrical measuring circuit and connecting the other electrode to an electrical earth.