Abstract: An apparatus for measuring the level of the interface between two different media in a reservoir comprises a vibratory element adapted to contact both media on all sides, and an amplifier circuit which together with the vibratory element forms an oscillator circuit in which the vibratory element is the frequency determining part. The vibratory element makes flexural vibrations at a resonance frequency. The apparatus further comprises a processing unit for measuring the momentary resonance frequency of the vibratory element and for deriving the level of the interface with respect to the vibratory element from said momentary frequency by means of the predetermined dependency of the resonance frequency on the depth of immersion of the vibratory element in the lower medium. The vibratory element is made as a plate-like element with a very small size with respect to the height of the reservoir.

Abstract: An apparatus for measuring a temperature comprises a first resistance, the resistance value of which depends on the temperature to be measured, a second resistance, a multiple switch with a plurality of inputs and an output, wherein the resistances each are connected to a corresponding input, a supply source which can be coupled with both resistances through a switch and a processing unit for controlling the switch and the multiple switch and for determining the temperature in dependence on the voltages measured at the supply source being switched on and off respectively, in the subsequent positions of the multiple switch. The output of the multiple switch is connected to an input of a voltage/frequency converter through a voltage source, an output of the voltage/frequency converter being connected to the processing unit.