Section 1: Transmitter Overview Page; General Description; Level Transmitter; Mli Mounted Transmitter - Emerson Magtech LTM−350 Series Instruction And Operation Manual

August 2020
Section 1: Transmitter Overview

1.0 General Description

The LTM-350 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 a digital output proportional to liquid
level in a tank. The optional temperature output is
configured via the HART communicator.
The Model number is LTM-350 followed by up to four
letters that can describe additional features such as
mounting configuration (G for Gage Mount, S for
Standalone), or communications protocol (FF for fieldbus).
Optional Features of the LTM-350 include:
•
Second digital output proportional to an interface
level (requires a second float of different specific
gravity)
•
Digital temperature
temperature and is typically used for display and/or
calculation of mass.
•
Advanced diagnostics and features highly beneficial
for commissioning, troubleshooting or monitoring.
•
A variety of lengths and wetted materials to
accommodate many different applications.
The Model LTM-351 is a Model LTM-350 that is contained in
a stainless steel housing.

1.1 Level Transmitter

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. MLI)
and strategically located within a certain longitudinal
distance from 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 and
digital HART signal.
proportional to the liquid level in the tank.
output gives the
This analog output is precisely
The LTM-350 may be strapped to the side of the Magtech
MLI series (Magnetic Level Indicator). In such an installation,
it is used as an accessory transmitter for the visual level
indicator. The same float used to activate the magnetic level
indicator is also used to transmit a signal to the
piezoelectric sensor of the LTM-350.
In the illustration below, the transmitters may be calibrated
for the same range as the visual indicator on the MLI, or for
part of the range (See Section 3).
liquid
Typical LTM-350 Mounting Configuration on a MLI
When a companion Magnetic Level Indicator is not present,
the LTM-350 is inserted into the tank with its own float
around the sensor tube. A stilling well may be optionally
used inside the tank.
5
Reference Manual
L231040 Rev AD

1.2 MLI Mounted Transmitter

1.3 Direct Insertion Transmitter