Patent ID: 7477157
Filing Date: 2009-01-13
Classification: H04L

Abstract:
1. An apparatus for determining and/or monitoring at least one physical or chemical variable of a medium in a container, having: at least one sensor unit, which produces a measurement signal with at least one piece of process-variable-dependent, basic information; and at least one evaluation unit, which, from the measurement signal of said sensor unit, determines a measured value for the process variable, and which produces at least one output signal, wherein: said output signal carries at least one piece of information concerning whether the measured value is greater or smaller than at least one predeterminable limit value; said output signal lies within a predeterminable signal range; at least one first and one second modulation range within the signal range are provided; said evaluation unit is formed such that it modulates said output signal within the first or second modulation range, at least with the basic information of said measurement signal; said evaluation unit modulates said output signal within the first modulation range when the process variable is smaller than the limit value; said evaluation unit modulates said output signal within the second modulation range when the process variable is greater than the limit value; said output signal lies within the first modulation range when the process variable is smaller than the predetermined limit value; said output signal lies within the second modulation range when the process variable is greater than the predetermined limit value; a separation range lies between the two modulation ranges; said measurement signal is an electrical signal which carries a resonance frequency of said sensor unit; said evaluation unit is formed such that it modulates said output signal with the resonance frequency, or with a change of the resonance frequency, of said measurement signal; and said sensor unit comprises at least one mechanically oscillatable unit, whose resonance frequency depends at least on the amount of covering of said mechanically oscillatable unit by the medium.