Data Sheet

DLC3010 Digital Level Controller

D102727X012

Product Bulletin

11.2:DLC3010

August 2014

Principle of Operation

The DLC3010 digital level controller is a loop-powered

instrument that measure changes in liquid level, level

of an interface between two liquids, or density of a

liquid. A level, density, or interface level change in the

measured fluid causes a change in the displacer

buoyancy (figure 5). This change is transferred to the

torque tube assembly. As the measured fluid changes,

the torque tube assembly rotates.

The rotary motion of the torque tube is transferred to

the digital level controller lever assembly (figure 5).

The rotary motion moves a magnet attached to the

lever assembly, changing the magnetic field that is

sensed by the Hall-effect sensor. The sensor converts

the magnetic field signal to a varying electronic signal,

which is processed digitally to provide linearity

corrections, sensitivity adjustment, and temperature

compensation.

The signal is interpreted as a buoyancy change by

reference to the stored torque rate, coupling point,

and moment arm data. The buoyancy change in turn is

interpreted as a level, interface, or density change by

reference to stored displacer volume, specific gravity,

and displacer length data. In level or interface modes,

the correction for displacer motion is then added, as

well as user-supplied offset to change the PV reference

from the bottom of the displacer or correct for a

coupling point error.

The resultant primary variable (PV) is then compared

to PV alarm thresholds (if enabled) and used to set

status bits and/or trigger the analog alarm current. If

the alarm is not triggered, the PV is used to generate

4-20 mA analog and 0-100% range digital signals by

reference to the stored upper and lower range values.

The resultant analog command is limited at the

saturation values to allow discrimination between

saturated and alarm signals.

Figure 5. Cutaway View of Fisher 249 Displacer Sensor with FIELDVUE DLC3010 Digital Level Controller

W1389-1

DISPLACER

TORQUE TUBE

E1471