E3A-MA3A-H11 Datasheet, PDF (27/48 Pages) Magnetrol International, Inc. – Digital E3 Modulevel with HART® and PACTware™ Communications Liquid Level Displacer Transmitter

3.0 Reference Information
Wiring Board
Moving
LVDT Core
Printed
Circuit Board
Enclosing Tube
Range Spring
Electronics
Enclosure
LVDT
Display
Keypad
Stem
This section presents an overview of the operation of the
E3 Electronic Modulevel Displacer Level Transmitter,
information on troubleshooting common problems, listings
of agency approvals, lists of replacement and recommended
spare parts, and detailed physical, functional, and perform-
ance specifications.
3.1 Description
The E3 Modulevel is a loop-powered, two-wire, 24 VDC
level transmitter which utilizes simple buoyancy principles
in combination with a precision range spring and a highly
accurate LVDT (linear variable differential transformer) to
detect and convert liquid level movement into a stable 4–20
mA output signal. The electronics are housed in an
ergonomic, dual-compartment enclosure which is angled for
ease of wiring and calibration.
3.2 Theory of Operation
Displacer
External cage
Figure 14
Electronic Modulevel
Components
The Electronic Modulevel Displacer Level Transmitter relies
on the principles of buoyancy to convert mechanical move-
ment to an electronic output. See Figure 14.
3.2.1 Displacer/Range Spring
According to Archimedes principle, the buoyancy force act-
ing on an object immersed in liquid is equal to the mass of
the liquid displaced. As the level changes, the volume of
displacer submerged in the liquid changes, thus varying the
buoyancy force acting on the displacer. This change is
detected by the precision range spring from which the dis-
placer hangs, causing it to elongate or compress. The change
in spring length causes movement of a special LVDT core
which is mounted on a rigid stem attached to the spring.
3.2.2 LVDT
E3 Modulevel utilizes highly precise LVDT technology to
convert the movement of the LVDT core within the LVDT
to a stable 4–20 mA output signal. The position of the core
with respect to a primary and two secondary windings with-
in the LVDT, induces a voltage in each winding. The com-
parison of the induced voltages within the microprocessor
of the E3 results in very accurate level output.
48-635 E3 Modulevel Displacer Level Transmitter
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