4 | GE Oil & Gas
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1.
Description - Operation
The 12400 Series Digital Level Transmitter/Controller is a high performance, easy-to-set instrument based on a modular design
that permits quick, low-cost upgrades as new features are developed and as your needs change.
1.1. PRINCIPLE OF OPERATION
The Masoneilan 12400 Series instrument from GE is a 2-wire, loop powered, digital displacement level transmitter/controller
with HART
®
communication that uses field proven buoyancy and torque tube principles.
A change in liquid level varies the apparent weight of the displacer (130), which increases or decreases load on the torque tube
(136) by an amount directly proportional to the change in liquid level. The resulting rotation of the torque rod (138), seen in
Figure 1, modifies the magnetic field of a frictionless, non-contacting sensor (40). The signal generated by the sensor varies
current in the loop in proportion to the level in the vessel.
1.2 SIGNAL PROCESSING
The sensor analog signal is converted into an error-free digital signal for processing by the on board micro-controller. After
signal processing, the digital result is converted to analog output signals for use by configuration and options.
Transmitter model:
♦
The 4-20 mA analog output signal, available on the AO_1 terminal, is the level or interface measurement signal with HART
®
communication.
Transmitter model with two (2) adjustable switches and second 4-20mA analog output
:
♦
T
he two 4-20 mA analog output signals, available on the AO_1 and AO_2 terminals, are the level or interface measurement signal, with
HART communication (AO_1 only).
♦
DO_1 and DO_2 terminals are two independent isolated digital switch outputs. They are user-adjustable and polarity sensitive.
Controller model with two (2) adjustable switches and second 4-20mA analog output:
♦
The 4-20 mA analog output signal, available on AO_1 terminals, is the controller output signal generated by a PID algorithm based on
error between the local setpoint and the level process variable. HART communication is available on AO_1.
♦
T
he 4-20 mA analog output signal, available on the AO_2 terminals, is the level or interface measurement signal. No HART
communication.
♦
DO_1 and DO_2 terminals are two independent isolated digital switch outputs. They are user-adjustable and polarity sensitive.
The 12400 instrument enables retrofit of existing pneumatic or digital level instruments (see Section 9.2).
PARTS REFERENCES
40
Non contact Sensor
135 Torque arm
55
Magnet
136 Torque tube
130 Displacer
137 Torque tube housing
131 Displacer chamber
138 Torque rod
Figure 1 – Diagram of principle
IMPORTANT
Options described above are operable only if they have been ordered initially. You cannot add them later on
site (see numbering system Section 3.2).
