| 摘要 |
The instant invention provides an improved method for determining the streaming velocity of a streaming liquid by injecting a thermopulse into the liquid and measuring Its transit time. The pulse is detected by its ascending flamk at downstream points and by its ascending or descending flank at its point of injection. For short transit times, provision is made to eliminate the neat up time of the heating wire imparting the pulse from the transit time measurement. The liquid may stream continuously or discontinuously, and if the latter, provision is made to decay measurement on initiation of flow until the flow pattern has stabilized. The time is determined by counting pulses from a pulse generator during the period the pulse is traveling between the point of injection and a detection point or between two detection points. This procedure enables more precise measurement of flow than has heretofor been possible. The present invention is also concerned with a method and an apparatus which permit accurate and reproducible dosing for multicomponent liquid systems. Previously known systems were dependent upon such variables as pump pressure, density, viscosity and temperature of the components but the present invention provides a monitoring and metering system independent of these variables and is able to provide reproducible dosing at the low(50 to 200 cm3/min, for example) flow rates utilized in spray lacquering. The method is based on the fact that the particular components are conveyed through separate pipes into a mixing chamber. The flow rate at least one of the pipes is determined by the above procedure and the flow in the other pipes is then adjusted automatically to be in a fixed ratio to the first flow. The so-measured transit time is converted into an inversely proportional voltage and the flow rate in the other pipes is adjusted proportionally to this voltage. An apparatus is provided for practicing the method. The apparatus comprises flow measuring elements which are electrical connected in the pipes leading to the mixing chamber. |
