Acam-Messelectronic Gmbh

Augustin Braun

Friedrich Bahnmüller

Friedrich Bohnmüller

For measuring unknown capacitances, which exist in capacitive sensors, such as pressure, moisture, inclination sensors and the like, the invention proposes a capacitance measurement method, in which a capacitance to be measured is charged and discharged across a resistor and the charging or discharging time up to a preset voltage value is measured and in which the charging/discharging times of a known reference capacitance and stray capacitances are measured across a resistor. The invention also proposes a circuit for measuring an unknown capacitance to be measured and having a voltage source, a resistor for charging or discharging at least the measuring capacitor, at least one switch for connecting and disconnecting the measuring capacitor with respect to the voltage supply and a time measuring device, in which switches are provided for connecting and disconnecting the measuring capacitor and at least one reference capacitor with respect to the circuit.

Method and device for measuring capacitances

A method for the temperature compensation of a resistance measuring bridge, such as in particular a Wheatstone bridge, is characterized in that a capacitor positioned between the input circuit and a resistance switching circuit of the Wheatstone bridge is successively discharge by means of at least one Wheatstone bridge resistor. In a device for the temperature compensation of a measuring bridge, particularly a Wheatstone bridge, having a measuring bridge and a compensating resistor in the input circuit, one or two switches are located in the resistance switching circuit branch of the measuring bridge as a contact point with the latter and a capacitor is located between the input circuit and the resistance switching circuit branch.

Method and device for the temperature compensation of a measuring bridge

In order in a method for measuring the resistance across discharge times of a capacitor to eliminate the interfering influence of the resistance values of electronic switches, the invention provides for a capacitor to be repeatedly charged and discharged and the charging or discharging time is measured by means of at least one resistor (R , R , R ) and at least one first switch (S , S or S ) connected in series therewith, at least one second switch (S , S or S ) connected in series with the resistor (R , R or R ) and juxtaposed, parallel-connected switches (S S or S S or S S ) connected in series with the resistor (R , R or R ). For performing the method, the invention provides a circuit arrangement for resistance measurement having at least one capacitor (C) and at least two resistors (R , R , R ) connected in parallel thereto and with the resistors (R , R , R ) is in each case associated in series a switch (S S or S ) and with the first switch (S S or S ) is connected in parallel at least one second switch (S , S or S ).

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Karlsdorf-Neuthard, Germany

Augustin Braun