| 摘要 |
<p>A method and apparatus to control the flow of liquid through a valve, especially at very low levels down to about 0.5 ml/hour, by monitoring the liquid level in a column of liquid using a sensor, for example a photo-electric cell, which is moved along the column at a predetermined rate corresponding to the liquid flow rate desired, generating a signal from the sensor which is representative of the liquid level, and using the signal to control the opening and closing of the valve to maintain the liquid flow at the desired rate.</p> |
