| 摘要 |
<p>A method of indicating level of material in a vessel includes coupling a probe to the vessel such that capacitance at the probe varies as a function of material level in the vessel. A periodic electrical signal at fixed frequency is applied to the probe such that operating characteristics of the signal vary as a function of capacitance at the probe. Material level is detected as a function of the operating characteristics of the signal. During a calibration mode of operation, the fixed frequency of the periodic electrical signal is varied to optimize sensitivity at the probe. In a preferred embodiment of the disclosure, this is carried out by applying the periodic electrical signal to the probe over a selected frequency range during the calibration mode of operation and identifying a frequency within this range at which the probe is most sensitive to changes in capacitance at the probe. The fixed frequency during a measurement mode of operation thereafter is set to this identified frequency.</p> |
