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©2013 Technical Marine Service, Inc. LC-100 V2.97
General Information
Bubblers are one of the oldest remote level sensing systems. They operate by measuring
the air pressure required to blow bubbles from the end of a pipe that is a fixed distance near
the bottom of the tank. This pressure reading is converted to liquid depth if the specific
gravity of the measured fluid is known. This ability, to measure the fluid depth remotely is
one of the most important characteristics of bubblers. No sensitive electronics or machinery
are submerged or exposed to the tanks contents, only a piece of pipe that is constructed of
materials compatible with the fluid is placed in the tank.
Older bubbler systems were of the continuous flow type and they constantly admitted air into
the bubbler pipe. The tank measurement was then indicated by a pressure gauge. This
pressure gauge was often a mercury filled manometer. The continuous flow of air can cause
measurement errors if the flow rate is too high and continuous flow systems usually cannot
detect problems in the bubbler pipe system.
The LevelCom 100 is a microprocessor based pulsed bubbler system. In contrast to
continuous flow bubblers the LevelCom 100 uses measured charges of air (pulses) to verify
that the bubbler pipe is clear of liquid. Pressure readings are taken with no air flow,
eliminating flow rate caused errors, and allowing the detection of leaks in the sense line
system. The LevelCom 100 measures the static pressure at the end of the bubbler pipe.
Using the programmed value for the liquid specific gravity this pressure reading is converted
to a depth reading. This raw depth reading is then converted for display in engineering units
of measure which include:
• Depth expressed in inches, feet, feet/inches, centimeters or meters
• Volume expressed in gallons, liters, cubic feet or barrels
• Weight expressed in short, long or metric tons
Volume and weight are calculated through a user configured tank curve. Any unit may be
displayed in ullage or innage.
The LevelCom 100 calculates the values and displays them on the front panel as 0 to 100%
of tank depth on the bar graph indicator and in the desired units of measure (as depth,
volume or weight) on the digital display.
The instrument is available in four sensor ranges:
• 0 to 31 feet (0 to 9.45 meters)
• 0 to 62 feet (0 to 18.9 meters)
• 0 to 90 feet (0 to 27.4 meters)
• 0 to 180 feet (0 to 54.9 meters)
The LevelCom 100 uses computer controlled solenoid valves, admitting pulses of air to the
system only as needed to balance against changes in the liquid level. The unit can be
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