arrangement to generate an messausgangssignales whose altitude is linear on the size of a measured resistance abhaengt

摘要

A digital ohmmeter having a differential amplifier with a capacitor connected between the output and the inverting input to form an integrator. A source of DC voltage is connected to a series circuit including the unknown resistor and to a switch which selectively connects the source to a second series circuit, an intermediate point of which is connected to the inverting terminal of the amplifier. The unknown resistor is connected to the noninverting input. The output of the amplifier is connected to logic circuit and counting means of the type used in dual slope integrating digital voltmeters, and others such as voltage-to-frequency converters, with the logic means having an output to control the switch means. The switch is open for a fixed interval and closed for a variable interval, which variable interval is counted as a measure of the input resistance. In this embodiment, the two series resistance circuits form a bridge when the switch is closed. In a second embodiment an additional switch connects the second series circuit to ground when it is disconnected from the source. In either embodiment the resistance value is linearly proportional to the length of the variable interval of time multiplied by a constant, the constant being determined by the fixed resistors in the two series circuits.