LD301 - Operation and Maintenance, Instruction Manual
3.10
In order to find the square root, the LD301 configurable parameters are: cutoff point defined at a certain
pressure expressed as % and the cutoff mode, hard or bumpless.
OUTPUT
100%
BUMPLESS
HARD
CUTOFF
POINT
100%
CALIBRATE
SPAN
Y = 10 x
Figure 3.5 – Square Root curve with Cutoff point
NOTE
In bumpless cutoff mode the gain below the cutoff point is given by the equation:
cutoff
G
10
For example, at 1% the gain is 10, i.e., a 0.1% error in differential pressure, gives a 1% error in Flow
reading. The lower the cutoff, the higher is the gain.
The measurement of the bidirectional flow is useful when it is needed to measure the flow in the pipe in
both directions. For example, in tank maneuvering there are several pipes where the direction of the fluid
may vary. In this case, LD301 has the bidirectional flow measurement function. This function treats the
flow, no matter what its direction is, as if it were positive. Thus, it is possible to extract the square root
and measure the bidirectional flow.
SQRT**3
- Square Root of the Third Power;
The output will be
3
1.0 x . This function is used in open channel Flow measurement with weirs or
flumes.
SQRT**5
- Square Root of the Fifth Power. The output will be
5
001.0 x . This function is used in
open channel Flow measurement with V-notch weirs.
It is possible to combine the previous functions with a table. The flow can be corrected according to the
table to compensate, for example, the variation of Reynolds number at the flow measurement.
TABLE - The output is a curve formed by 16 points. These points may be edited directly on the XY
Table of the LD301. For example, it may be used as a camber table for tanks in applications where
the tank volume is not linear in relation to the measured pressure;
SQRT & TABLE
- Square root and Table. Same application as square roots, but also allows
additional compensation of, e.g., varying Reynolds number.
SQRT**3 & TABLE
- Square Root of the Third Power AND TABLE;
SQRT**5 & TABLE - Square Root of the Fifth Power AND TABLE.
TABLE & SQRT – This function provides bidirectional flow measurement (piping flow measurement
in both ways). This function is available for version 6.05 or above firmware.
Example:
There is a flow on the positive direction (high pressure on the H side) with a 0 to 400 mbar DP and a flow
on the negative direction (high pressure on the L side) from 0 to 100 mbar. For these data make the
range lower value equal to -100 mbar, complete the table below, and always including the 0 per cent
pressure value, namely 20 per cent. Insert the data on the transmitter.
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