PD6720 Field-Mount Loop-Powered Rate/Totalizer
Instruction Manual
20
Advanced Function Selection
(
FUNCTN
)
The
Advanced Function
menu is used to select the
advanced function to be applied to the input: linear,
square root, programmable exponent, or round
horizontal tank volume calculation. The multi-point
linearization is part of the linear function selection.
Meters are set up at the factory for linear function with
2-point linearization. The linear function provides a
display that is linear with respect to the input signal.
Multi-Point Linearization (
lnear
)
Up to 32 linearization points can be selected under
the
Linear
function. The multi-point linearization can
be used to linearize the display for non-linear signals
such as those from level transmitters used to
measure volume in odd-shaped tanks or to convert
level to flow using weirs and flumes that require a
complex exponent. These points are established via
direct entry (
SCALE
) or with a live calibration signal
source (
CAL
).
Multi-Point Scaling (
SCALE
)
The multi-point scaling is entered after selecting the
number of points (
noPtS
). The input signal levels
(
InP 1-32
) for up to 32 points, along with the
corresponding meter reading (
dSP 1-32
) should be
entered for each linearization point.
Multi-Point Calibration (
CAL
)
The meter can be calibrated using a current source
instead of using input scaling. This process will
override previously programmed scaling points.
Apply a live signal using a known accurate signal
source (
InP
1-32
) and then enter the corresponding
meter reading (
disp 1-32
) for that input signal level.
The use of a calibrated signal source is strongly
recommended.
Important Navigation Note
After entering the last display value, the linearization
entries must be saved (
SAUE?
) before they are put into
effect. However, you may move past this selection
using the Up arrow key if you need to go back and
correct and earlier entry. Once confident in the entries,
you must navigate back to the Save menu screen
(
SAUE?
) and press the Enter key to save the changes.
Square Root Linearization (
Squar
)
The square root function can be used to linearize
the signal from a differential pressure transmitter
and display flow rate in engineering units.
PD6720 Displaying Flow Rate by Extracting Square Root
from DP Transmitter Signal.
Low-Flow Cutoff (
CUTOFF
)
The low-flow cutoff feature allows the meter to be
programmed so that the often-unsteady output from a
differential pressure transmitter, at low flow rates,
always displays zero on the meter. The default cutoff
is zero to prevent negative readings, but this may be
overridden to allow them.
The cutoff value may be programmed from -0 to
99999. Below the cutoff value, the meter will display
zero. Selecting either square root or programmable
exponent will set the cutoff value to 0. Program the
cutoff value to 0 to disable.
