© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

4.5.4 Ullage Sensors

It will often be necessary to determine the degree to which a fluid storage tank is full or empty. In most circumstances, an ullage sensor may consist of a simple static pressure sensor embedded in the tank wall, with readout calibrated according to the van der Waals equation for gases and liquids (Section 10.3.2). A fractal network of chemical sensors permeating the internal volume of the tank could provide continuous readouts of local concentration which could be integrated to estimate total storage in the tank. The force required to rotate a paddle inside the tank would increase as a tank was filled, due to the increase in net viscosity of the contents (Section 9.4.1.1). Transmission time of thermal or acoustic pulses might also give some measure of fluid concentration and physical phase. C. Phoenix suggests storing liquids in a piston, allowing direct and precise molecular volume readout, in designs where this is convenient; in theory, a piston that slides the minimum measurable distance of ~10 pm (Section 4.3.1) within the 2-nm-diameter throat of a water-filled cylinder could detect the removal of a single water molecule from the column.

Last updated on 17 February 2003