Emerson FISHER FIELDVUE DLC3010 Instruction Manual page 46

DLC3010 Digital Level Controller
Configuration
May 2018
Figure 4‐4. Example Saturated Water Curve Plotted with Values from Table 4‐2
-18 30
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0 100
E0369
You can enter up to 10 temperature and specific gravity pairs in the table. The table entry function is terminated by
entering zero for the specific gravity. Keep this in mind when setting up a table for a upper fluid, such as steam,
whose specific gravity approaches 0 at lower temperatures.
The resolution of the table entry for specific gravity is 5 decimal places. This means the smallest specific gravity
value you can enter is 0.00001, which should be sufficient to allow a starting temperature around 15.6 _C (60 _F)
for the steam specific gravity table.
The example set of tables given are generated by visually laying linear segments over a reference curve, and are not
guaranteed to provide any particular accuracy. They are provided to illustrate the guidelines for developing your
own table.
1. Establish a table for the fluid(s) you are using over the expected operating range of process temperature. This
allows you to make best use of the maximum of ten points to obtain the accuracy you require. If your fluid
specific gravity is very linear over the operating temperature range, two data points may be sufficient. (The
correction algorithm provides linear interpolation between data points, and bounds the result at the table end
points.)
2. Pick points closer together in regions of higher slope.
3. Pick linear segments that distribute the error equally on each side of the true curve.
Enter values in the specific gravity tables.
Enter Constant SG allows you to define fluid density/densities by constant values. No temperature compensation is
applied.
Measure SG is only visible if PV is Liquid Level.
If specific gravity information for the process fluid is not available, an instrument and sensor combination that has
been previously calibrated can be used to measure the fluid density. You must be able to manipulate the level and
externally measure it to have the instrument measure the specific gravity. First capture a new zero reference angle
at the zero process condition for the unknown fluid(s), then run this procedure. If the actual process application is
46
TEMPERATURE _C
100 200
200 300 400 500
TEMPERATURE _F
300 380
600 700
Instruction Manual
D102748X012