Abstract: In a circuit for an ionization vacuum gauge having a thermionic filament, a control circuit receptive of a control current for controlling the filament and a switch for applying the control current to the control circuit, a circuit is provided for indicating a filament interruption independent of the state of the switch. The circuit includes at least one resistor by-passing the switch to provide a continuous sensing current to the filament and a detector for detecting the interruption in the sensing current and for indicating such an interruption.

Abstract: A measuring amplifier device is provided with an input circuit producing different functions of an input signal in order to permit output signals in different measuring ranges to be produced. The circuit can be constituted by an operational amplifier having a feedback connection composed of a series arrangement of several elements each defining a particular measuring range together with subtraction stages forming signals corresponding to each range, or by a plurality of diodes or diode-resistor networks connected to divide the input signal between them and each defining a different measuring scale.