Instruction Manual

Instruction Manual
D103434X012
Principle of Operation
November 2014
71
Appendix A Principle of Operation1‐1‐
Digital Level Controller Operation
The DLC3020f digital level controller is a fieldbus‐powered instrument that measures liquid level or interface between
two liquids. As the liquid level surrounding the displacer rises (figure A‐1), the torque tube rotates clockwise; the
reverse action occurs when the liquid level is lowered. The rotary motion of the torque tube is transferred to the lever
assembly (figure A‐2) which rotates an attached magnet array. The sensor module converts the changing magnetic
field to a digital signal, which is ambient temperature compensated, linearized, and sent to the electronics assembly.
Figure A‐1. Typical Sensor Operation
TORQUE
TUBE
DISPLACER
249 SENSOR (SIDE VIEW)
W1389‐1
MOUNTING FLANGE
FOR DLC3020f
The electronics assembly actively compensates for changes in liquid density due to process temperature variances
based on a process temperature input from a transmitter or a direct‐wired RTD. The electronics assembly also
computes the process variable (PV) and manages F
OUNDATION fieldbus network communication.
The terminal box contains fieldbus, simulation, and RTD terminal connections. Circuits in the terminal box also provide
reverse polarity, transient power surge, and electromagnetic interference (EMI) protection.
The LCD meter displays the process variable (PV) and various instrument alerts, as configured.