| 摘要 |
In a mass flowmeter operating according to the Coriolis principle pickups are used for sensing the movements of the oscillating tubes. In conventional flowmeters with two tubes where the deflection of the two tubes in relation to each other is measured, the calculated mass flow may be wrong if the pickups are not quite identical or if there are flow limiting deposits in one tube but not in the other. This means that the common mode oscillations of the tubes gives an unwanted signal contribution. Instead of measuring absolute values, often in relation to the chassis, it is according to the invention proposed to perform a differential reading of the oscillating tubes whereby the sensitivity to the common mode oscillations of the tubes is considerably reduced. The differential reading is obtained in placing a measuring device, e.g. a strain gauge, on each of the two plates which mechanically connects the two tubes. In measuring the elongation of the plates due to the Coriolis force an expression of the mass flow can be obtained which is essentially insensitive to the common oscillation of the tubes. A further advantage of the invention is that cabling is simplified as no cables are to be placed on the tubes. The invention also relates to a method which makes use of the mass flowmeter.
|
