Emerson LTM-300 Manuel D’Utilisation

The  LTM-300  is  an  electronic  field  instrument,  suitable  for  installation 
in  hazardous  and  non-hazardous  industrial  areas.    Testing  and 
certification has been obtained from different agencies for installation 
in specific areas.   

This instrument is a two wire, loop powered smart transmitter,  designed 
to measure and transmit an analog 4-20 mA signal and two digital outputs 
(optional) proportional to liquid level in a tank.  The optional temperature 
output is configured via the HART communicator. Interface is auto-detect. 
Note: Both floats have to be present for auto-detection. The complete 
assembly includes a dual compartment explosion proof enclosure, and 
attached sensor tube.

 

Optional Features of the LTM-300 include:

• 

Second digital output proportional to an interface level (requires 
a second float of different specific gravity)

• 

Digital  temperature  output  gives  the  liquid  temperature  and  is 
typically used for display and/or calculation of mass.

• 

A variety of lengths and wetted materials to accommodate many 
different applications.

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Mass or Volume Information

Product Serial Number 

Magtech assigns a unique serial number for each unit. The first two digits 
indicate the month of production followed by two digits, indicating the 
year of production. For example, serial number 0606 / 1234 describes a 
unit manufactured in June of 2006 with a serial number 1234.

In its simplest configuration, a single-purpose float rides up and down 
the sensor tube, totally surrounding it.  A multi-purpose float may also 
be used to activate the sensor, such a float being placed inside a liquid 
isolation pipe, (i.e. Mag-Gage) and strategically located within a certain 
longitudinal distance form the sensor tube.  In either case, the float has 
a somewhat lighter specific gravity than the liquid whose level is to be 
measured, so that it is partially submerged at the interface of interest.  
As the tank level changes, the float tracks the change and continuously 
activates the sensor in the tube.  The electronics in the housing process 
the changing signal and update an analog 4-20 mA output.  This analog 
output is precisely proportional to the liquid level in the tank. 

 

The LTM-300 may be strapped to the side of the MagTech LG series 
magnetic level indicator.  In such an installation, it is used as an 
accessory transmitter for the visual level gage.  The same float used 
to activate the magnetic gage is also used to transmit a signal to the 
magnetostrictive sensor of the LTM-300.

 

In  the  above  right  shown  installations,  the  transmitters  may  be 
calibrated for the same range as the visual indicator on the Mag-Gage, 
or for part of the range (See Section 3).

When  a  companion  magnetic  gage  is  not  present,  the  LTM-300  is 

inserted  into  the  tank  with  its  own  float  around  the  sensor  tube.    A 

stilling well may be optionally used inside the tank or, in case of high 

temperatures;  an  external  chamber  may  be  the  housing  of  the  tube 

and float assembly.

When a stilling well is used, care should be exercised when installing 

the tube to center it in the chamber so that the float can freely travel the 

entire length of the probe.  Stilling wells are  required for transmitters 

over 10 feet. 

Up  to  two  floats  may  be  used  with  the  LTM-300.   The  second  float 

will typically sense the interface level of the heavier of the two fluids 

in  the  tank.   The  specific  gravity  of  the  second  float  will  be  such  that 

it can be totally immersed in the lighter fluid.

When two floats are used, a minimum separation of about three inches 
is recommended to prevent interference between floats.

The calibration range of the transmitter may be field stored in non-

volatile memory by using the float and push buttons.  The push 

buttons are located on the front panel inside the condulet.  See 
section on Calibration for more details.

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