| 摘要 |
<p>Amplitude-balanced input signals (I1 and I2) from two pick-up coils (10,11) spaced along a vibrating tube mass flow transducer are used to form sum and difference signals (S and D). These are multiplied by quadrature and in-phase signals (Q and I) respectively in multipliers (21,22), the multiplying signals being generated by a phase-locked loop (16,17,18) locked to the sum signal (S). The in-phase signal (I) provides the drive signal for a drive coil (12) of the transducer. The produce signals (PS and PD) from the two multiplier (21,22) are smoothed in low pass filters (23,24) to provide sum and difference voltages (VS and VD). Mass flow rate is proportional to the phase difference (represented by the ratio of these voltages) divided by the frequency of the I signal. The density of the fluid in the transducer is indicated by the frequency of the I signal.</p> |
