| 摘要 |
PURPOSE: To obtain a concentration of a fluid irrespective of influences by a suspended matter and air bubbles, by comparing each apparent phase delay at a time point and a next time point with an upper range and a lower range of a phase angle, obtaining a revolution number, processing the revolution number thereby to obtain a true phase delay. CONSTITUTION: A phase difference-measuring circuit 35 compares a microwave transmitted wave and a microwave received wave, measures a reference phase delayθ1 to a reference fluid, and stores the delay in a phase difference- correcting circuit, 36. Thereafter, the circuit, 35 inputs in the circuit 36 an apparent phase delayθ2 ' for a fluid to be measured, e.g. every 5 seconds. The circuit 36 compares each phase delayθ2 ' at a time point and a next time point with a preset upper range of a phase angle close to 360 and a preset. lower range of the phase angle close to 0, thereby to obtain a revolution number (n). Tame circuit 36 operatesθ2 =θ2 '+n×360 and obtains a true phase delayθ2 . A phase differenceΔθ=θ2 -θ1 is calculated, which is inputted to a signal- converting circuit 38. A concentration is calculated in this manner.
|
