SMAR LD291, Operation And Maintenance Instruction Manual

Page: 33 / 84

Configuration
3.7
VARIABLE UNITS
Pressure
inH2O, InHg, ftH2O, mmH2O, mmHg, psi, bar ,mbar, g/cm
2
, kg/cm
2
, Pa,
kPa, Torr, atm, MPa, in H2O
4
, mmH2O
4
Volumetric Flow
ft
3
/min, gal/min, I/min, Gal/min, m
3
/h, gal/s, l/s, MI/d, ft
3
/s, ft
3
/d, m
3
/s, m
3
/d,
Gal/h, Gal/d, ft
3
/h, m
3
/min, bbl/s, bbl/min, bbl/h, bbl/d, gal/h, Gal/s, I/h, gal/d
Velocity ft/s, m/s, m/h
Volume gal, liter, Gal, m
3
, bbl, bush, Yd
3
, ft
3
, In
3
, hl
Level ft, m, in, cm, mm
Mass gram, kg, Ton, lb, Sh ton, Lton
Mass Flow
g/s, g/min, g/h, kg/s, kg/min, kg/h, kg/d, Ton/min, Ton/h, Ton/d, lb/s, lb/min,
lb/h, lb/d
Density
SGU, g/m
3
, kg/m
3
, g/ml, kg/l, g/l, Twad, Brix, Baum H, Baum L, API, %
Solw, % Solv, Ball
Others cSo, cPo, mA, %
special 5 characters
Table 3.2 – Available User Units
Should a special unit other than those presented on Table 3.2 be required, the LD291 allows the user
to create a new unit by entering up to 5 alphanumeric digits.
The LD291 includes an internal feature to enable and disable the User Unit.
Example : transmitter LD291 is connected to a horizontal cylindrical tank (6 meters long and 2 meters
in diameter), linearized for volume measurement using camber table data in its linearization table.
Measurement is done at the high-pressure tap and the transmitter is located 250 mm below the support
base. The fluid to be measured is water at 20
°
C. Tank volume is: [(
π
.d
2
)/4].l = [(
π
.2
2
)/4]
π
.6 = 18,85 m
3
.
The wet tap shall be subtracted from the measured pressure in order to obtain the tank level.
Therefore, a calibration without reference shall be carried out, as follows:
In Calibration :
Lower = 250 mmH
2
O
Superior = 2250 mmH
2
O
Pressure unit = mmH
2
O
In User Unit:
User Unit 0% = 0
User Unit 100% = 18.85 m³
User Unit = m³
When activating the User's Unit,
LD291 it will start to indicate the new measurement.
Table Points
If the option TABLE is selected, the output will follow a curve given in the option TABLE POINTS. If you
want to have your 4-20 mA proportional to the volume or mass of fluid inside a tank, you must
transform the pressure measurement "X" into volume (or mass) "Y" using the tank strapping table, as
shown in Table 3.3.
POINT LEVEL (PRESSURE) X VOLUME Y
1 - -10% - -0.62%
2 250 mmH
2
O 0% 0 m
3
0%
3 450 mmH
2
O 10% 0.98 m
3
5.22%
4 750 mmH
2
O 25% 2.90 m
3
15.38%
5 957.2 mmH
2
O 35.36% 4.71 m
3
25%
6 1050 mmH
2
O 40% 7.04 m
3
37.36%
7 1150 mmH
2
O 45% 8.23 m
3
43.65%
8 1250 mmH
2
O 50% 9.42 m
3
50%
… … … … …
15 2250 mmH
2
O 100% 18.85 m
3
100%
16 - 110% - 106%
Table 3.3 - Tank Strapping Table
As shown on the previous example, the points may be freely distributed for any desired value of X. In
order to achieve a better linearization, the distribution should be concentrated in the less linear parts of
the measurement.