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Babbitt level
transmitters for the LG Series liquid level gauges are designed to
provide an analog output for continuous levelmonitoring and control.
Thesetransmitters mount on the outside of a level gauge chamber.
The units do not come into direct contact with the process. They can
be calibrated and servicedwithout shutting down your process.
These level transmitters are actuated by the magnets in the level
gauge float. As the float rises and falls with the process level,
the transmitters detect the position of the float, and provide a proportional
4-20mA output to your process control system or recorder.
LT-1 Transmitter
The LT-1 level
transmitter consists of a sensor tube made up of a string of resistors
and magnetically operated reed switches. There is a switch and resistor
every 1/2 inch along the length of the sensor tube. The circuit board containing the resistors and switches may be the
same length as the measured range or any portion thereof. The sensor
circuit is encapsulated in the stainless steel sensor tube. The transmitter
housing (rated for Class 1, Div 1, Groups C, D hazardous areas) is
mounted at the top of the sensor tube. As the magnetic float inside the level gauge chamber rises with increasing
fluid level, the reed switches close, thereby changing the resistance
in the circuit. A two-wire transmitter converts this resistance change
to a 4-20mA current signal corresponding to fluid level. Resolution
of the transmitter is 1/2 inch.
LTM-100 Transmitter
The
LTM-100 Series magnetostrictive level transmitter may be used as a
stand-alone top-mount level transmitter or may be mounted externally
on the LG series magnetic level gauge. It is typically used in applications
where precision accuracy and high repeatability is required. The unit
offers a HART protocol with the 2-wire 4-20mA output for level or
interface. The LTM transmitter consists of a sensor tube (typically 1/2"
316SS) which houses the waveguide. The waveguide is made to order
in lengths up to 20 feet, with longer waveguides available in a flexible
probe design, assembled in 8 foot sections. A low-power microprocessor
circuit, housed in an explosion-proof condulet, is used to generate
a current pulse down the waveguide. Liquid level is detected when
the magnetic field of the float interferes (restricts) with the current
pulse signal. Very precise level measurement is possible using this
magnetostrictive technology. Field calibration is simple with on-board zero and span push-buttons
or with conventional HART hand-held calibrators. The LTM-100 transmitters
simply mount to the side of the gauge chamber and is ideal for high-pressure
and high-temperature applications.
Flipper
/ Roller Option
In addition
to the standard magnetic follower style indicator, Babbitt also offers
a flipper or roller style indicator. These consist of a series of
small metal flags that are black on one side and yellow on the other.
As the magnetic float passes each flag with rising or falling liquid
level, the flag rotates 180 degrees to show the other color, yellow
indicating the liquid level and black the vapor space. These flags
are spaced every 0.4 inches (30 per foot) and give a very distinct
yellow column corresponding to the tank level. Red/Black flags are
also available. The flags rotate on a ceramic and stainless steel
bearing surface. They are housed in an extruded aluminum channel with
a recessed glass window. After assembly, the unit is purged with inert
gas (argon) and hermetically sealed. The assembly is custom made for
each level gauge and is one continuous piece up to 20 feet, with no
joints or blind spots. Babbitt flipper/roller indicators have been
tested through 50,000 cycles at float travel speeds from 10 feet per
minute to 800 feet per minute without a failure.
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