PD8-6060 Explosion-Proof Dual Analog Input Process Meter
Instruction Manual
55
Square Root Linearization
(
Square
)
The square root function is used to calculate flow
measured with a differential pressure transmitter.
The flow rate is proportional to the square root of the
differential pressure. Scale the meter so that the low
input signal (e.g. 4 mA) is equal to zero flow and the
high input signal (e.g. 20 mA) is equal to the
maximum flow.
Programmable Exponent
Linearization (
Prog E
)
The programmable exponent function is used to
calculate open-channel flow measured with a level
transmitter in weirs and flumes. The flow rate is
proportional to the head height. Scale the meter so
that the low input signal (e.g. 4 mA) is equal to zero
flow and the high input signal (e.g. 20 mA) is equal to
the maximum flow. This method works well for all
weirs and flumes that have a simple exponent in the
flow calculation formula. For weirs and flumes with
complex exponents it is necessary to use a strapping
table and the 32-point linearization of the meter.
For more information on how the Programmable
Exponent Linearization feature works, see the
Multi-Point Linearization (
Linear
)
Meters are set up at the factory for linear function with
2-point linearization. Up to 32 linearization points can
be selected for each channel 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 with complex exponent
32-Point Linearization
The most common way to linearize a non-linear signal
is to break it up into smaller ranges that are more
linear than the overall range. The ProtEX-MAX is
available with up to 32 points of linearization for each
channel. The linearization data can be imported from
an Excel spreadsheet or can be exported from
MeterView Pro to an Excel spreadsheet.
The above graphic illustrates Channel A input being
linearized with nine scaling points and Channel B
using the more standard two-point scaling method.
Note:
Scale values can also be imported from an Excel
spreadsheet.
