Helios PD2-6200 Analog Input Flow Rate/Totalizer
Instruction Manual
44
Select Menu (
SElEct
)
The
Select
menu is used to select the input signal
conditioner applied to the input (linear, square root,
programmable exponent, or round horizontal tank),
low-flow cutoff, and analog output programming. The
multi-point linearization is part of the linear function
selection.
Input Signal Conditioning (
Functn
)
The
Function
menu is used to select the input signal
conditioner 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 (
Linear
)
Meters are set up at the factory for linear function with
2-point linearization. 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 with complex exponent.
Square Root Linearization
(
Square
)
The square root function can be used to linearize the
signal from a differential pressure transmitter and
display flow rate in engineering units.
Programmable Exponent
Linearization (
Prog E
)
The programmable exponent can be used to linearize
the signal from level transmitters in open-channel flow
applications using weirs and flumes.
Application: Open Channel Flow
The PD2-6200, in combination with an ultrasonic level
transmitter, makes for an economical way to measure
and display open channel flow rate and total in most
weirs and flumes. A guide such as the ISCO Open
Channel Flow Measurement Handbook can provide
the user with all the information needed: the exponent
used in the flow equation for the desired flow units
and the flow rate for any given head height. For
example, to display the open channel flow rate from a
3" Parshall flume, the ISCO handbook advises the
exponent is 1.547 and at the maximum head height of
3.0 feet, the flow rate is 3.508 MGD.
3" Parshall Flume Discharge Table with Head in
Feet
Formula: CFS = 0.9920
H
1.547
GPM = 445.2
H
1.547
MGD = 0.6411
H
1.547
Where:
H
= head in feet
Table 13-3
Head (Feet)
CFS
GPM
MGD
3.00
5.428
2436
3.508
ISCO Open Channel Flow Measurement Handbook, 3
rd
edition
With this information the PD2-6200 should be
programmed in the following fashion. This setup
assumes the level transmitter is programmed to
output 20 mA at the maximum head height of 1.10
feet; but any mA value at a head height with a known
flow rate may be used.
Function
Desire
Programming
Open Channel
Flow
3" Parshall flume
Set Programmable Exponent to
1.547
Flow Rate
Millions of
Gallons per Day
(MGD)
Set 4 mA = 0
20 mA = 3.508
Time base = Day
Total
Millions of
Gallons
Set Totalizer Conversion Factor = 1
(password protect “total” to avoid
accidental reset)
Non-Resettable
Grand Total
Program meter
so grand total can
never be reset
Set non-resettable grand total
password
Display
Display Flow
Rate, Total, and
Grand Total
Set upper display for Grand Total
and lower display to toggle
between rate and total.
