| 摘要 |
<p>In a transducer of pressure and density a resonantly vibratable tubular sensing element (10) is arranged to be excited into vibration by either a first drive coil A (11) or a second drive coil B (12) dependent upon a selection via a mode select line (14), which controls changover contacts (15). The sensor is maintained in resonant vibration by means of a feedback from a pick-up coil A (16) or a pick-up coil B (17) via sustaining amplifiers A (18) or B (19). When a drive is selected a signal at the resonant frequency of vibration (Fa or Fb) is available and the respective amplifier output (100 or 101). The arrangement of drive means A and pick-up means A (11,16) and drive means B and pick-up means B (12,17) is not the same, but is such that different modes of vibration are excited when each drive is selected. The modes are chosen each to have different sensitivity to first and second parameters, such as pressure and density. At least one of the modes is chosen to be a complex mode, having both axial and circumferential vibration components. The invention may be arranged to overcome the problem of for example a density transducer which would otherwise be sensitive to pressure changes or alternatively arranged to provide outputs for each parameter.</p> |
