| ABSTRACT:
The present electronic multi-purpose material level sensor is based
on time domain reflectometry (TDR) of very short electrical pulses. Pulses
are propagated along a transmission line that is partially immersed in
a liquid, powder, or other substance such as grain in a silo. The time
difference of the reflections at the start of the transmission line and
the air/liquid interface are used to determine levels to better than 0.01
inch. The sensor is essentially independent of circuit element and temperature
variations, and can be mass produced at an extremely low price. The transmission
line may be a Goubau line, microstrip, coaxial cable, twin lead, CPS or
CPW, and may typically be a strip placed along the inside wall of a tank.
The reflected pulses also contain information about strata within the liquid
such as sludge-build-up at the bottom of an oil tank. |