| 摘要 |
A method of "bubble measuring" levels in liquid storage tanks (49, Fig. 4) has been based upon supplying a constant mass flow of air through a tube (41) which has been mounted to discharge near the bottom of the tank (49). Such constant mass flow is obtained by supplying compressed air with a constant pressure to the measuring device, passing the air through a solenoid governed valve (25, Fig. 2) at the inlet to a pressure equalising volume (27, Fig. 2), measuring the pressure in said volume, transforming the pressure on both sides of the valve to electric signals, comparing said signals and using variations in the signals to govern the on-off valve (25) so as to obtain a constant mass flow. When this has been achieved the pressure after the solenoid valve is a function of the height of the liquid above the "bubble measuring" tube discharge end. |
