Milltronics OCM II PL-269, Instruction Manual

Page: 80 / 107

APPENDIX B
EXAMPLE 1: PARSHALL FLUME
This example considers a 6 inch Parshall flume which has a maximum flowrate of 1.87 MGPD at 1.24 feet
of head.
The transducer has been mounted 30 inches above the maximum operating head (at least 24 inches required).
The maximum liquid head is 1.24 feet = 14.88 inches.
The manufacturer‘s flow table shows flow as MGPD = 1.33 h
1.58
. Thus the flume is characterized by an exponent
of 1.58.
The distance from the transducer face to the zero-flow liquid level is 30 inches plus 14.88 inches = 44.88 inches.
An alarm is required for liquid levels in excess of 13.6 inches.
P0 = 1 Dimensions are in inches
P1 = 1 Temperature is Fahrenheit
P2 = 0 Exponential flow calculation
U0 = 1.87 MGPD (million gallons per day) at full head for 20mA output [or 1870 to have units
of 1000 gallons]
U1 = 3 Flowrate time units (per day)
U2 = 14.88 Full scale head in inches at 1.87 MGPD
U3 = 1.58 Exponent
P3 = 1 Display flowrate in run mode (F2)
P4 = 44.88 *Distance from transducer to 0 flowrate head in inches
P5 = 0 Calculate flow for all heads (no low head cut off)
P6 = 1 Fail safe high
P7 = 60 Fail safe after 60 seconds without an echo
P8 = 1 High alarm for high liquid head
P9 = 13.6 Head at which alarm is to occur
P10 = 3 Head must fall by 3 inches to cancel alarm
P11 = 0 Analog output is to represent flowrate
P12 = 20 Damping rate is 20 seconds for 100% change
P13 = 0 Analog output is 4-20 mA
P14 = 192 Optional logging file site identification number
P15 = 1 Totalizer multiplier [the floating point totalizer will move the decimal point to the right
until only whole units are displayed. Therefore it is advisable to use units of one
thousands rather than millions. [Conversely the units can be left at millions and the
multiplier set at .001].
Totalizer overflows every 534 days at full-scale flowrate of 1870 thousand gallons per day.
P16 to P18 not used in this example
* If AUTO ZERO calibration routine (F12) is used, entry of the current liquid head will cause P4 = 44.88
to be deduced and entered automatically.
N.B. Data Logging occurs automatically and requires no specific set-up. However, the data logs will be
meaningless if the CLOCK and CALENDAR are not set to the present time and date. If data logs will
never be used the clock and calendar need not be set. However for trouble shooting it may be useful
by noting when an abnormally high or low reading is occurring.
PL-269 9 – 2