SMAR ld301 - Units, Flow Functions, and Totalization

LD301 - Operation and Maintenance, Instruction Manual
3.8
 Place the Lower Limit in a value as far as possible from the present Upper Value and from the new
adjusted Upper value, observing the minimum span allowed. Adjust the Upper Value at the desired point
and, then, adjust the Lower Value.
This type of calibration is intended to prevent the calibration from reaching, at any moment, values not
compatible with the range. For example: lower value equals to upper value or separated by a value
smaller than the minimum span.
This calibration procedure is also recommended for zero suppression or elevation in those cases where
the instrument installation results in a residual measurement in relation to a certain reference. This is the
specific case of the wetted tap.
Engineering Unit Selection
Transmitter LD301 includes a selection of engineering units to be used in measurement indication.
For pressure measurements, the LD301 includes an option list with the most common units. The internal
reference unit is inH
2
O @ 20 ºC; should the desired unit be other than this one, it will be automatically
converted using conversion factors included in Table 3.1.
As the LD301 uses a 4 ½ digit display, the largest indication will be 19999. Therefore, when selecting a
unit, make sure that it will not require readouts greater than this limit. For User reference, Table 3.1
presents a list of recommended sensor ranges for each available unit.
CONVERSION FACTOR NEW UNITS RECOMMEND RANGE
1,00000 inH
2
O @20
o
C 1, 2, 3 and 4
0,0734241 inHg @ 0
o
C all
0,0833333 ftH
2
O @ 20
o
C all
25,4000 mmH
2
O @ 20
o
C 1 and 2
1,86497 mmHg @ 0
o
C 1, 2, 3 and 4
0,0360625 psi 2, 3, 4, 5 and 6
0,00248642 bar 3, 4, 5 and 6
2,48642 mbar 1, 2, 3 and 4
2,53545 gf/cm
2
1, 2, 3 and 4
0,00253545 kg/cm
2
3, 4, 5 and 6
248,642 Pa 1
0,248642 kPa 1, 2, 3 and 4
1,86947 Torr @ 0
o
C 1, 2, 3 and 4
0,00245391 atm 3, 4, 5 and 6
0,000248642 MPa 4, 5 and 6
0,998205 inH
2
O @ 4
o
C 1, 2, 3 and 4
25,3545 mmH
2
O @ 4
o
C 1 and 2
0,0254 mH
2
O @ 20
o
C 1, 2, 3 and 4
0,0253545 mH
2
O @ 4
o
C 1, 2, 3 and 4
Table 3.1 – Available Pressure Units
In applications where the LD301 will be used to measure variables other than pressure or in the cases
where a relative adjustment has been selected, the new unit may be displayed by means of the User
Unit feature. This is the case of measurements such as level, volume, and flow rate or mass flow
obtained indirectly from pressure measurements.
The User Unit is calculated adopting the working range limits as a reference, which is, defining a value
corresponding to 0% and another corresponding to 100% of the measurement:
 0% - Desired readout when the pressure is equal to the Lower Value (PV% = 0%, or transmitter
mode output equal to 4 mA);
 100% - Desired readout when the pressure is equal to the Upper Value (PV% = 100%, or transmitter
mode output equal to 20 mA).
NOTE
In most applications with wetted taps, indication is usually expressed as a percentage. Should readout
in engineering units with zero suppression be required, it is recommended to use the User Unit
feature for such conversion.