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Example 3: Transmit rate in GPM from 36.67 pulse/gallon turbine flow meter
Application:
Transmit rate in gallons per minute with three decimal places from a turbine flow
meter with a K factor of 36.67 pulses per gallon. Set analog output to 4 mA at 0 GPM and 20
mA at 30 GPM.
Solution:
•
Under Input+Display tab and Signal Input, set Mode to Rate, Function to “A only”, Gate
Time to 0.3 sec, and Time Out to 2 sec. Under Display, set Type to “Norml 999999”. Native
units will be pulses/sec (Hz).
•
Under Scaling tab, set Decimal Point tab to 111.111. If “Scale, Offset” is selected as scaling
method, set Scale to 1.63621 with a multiplier of 1000. The scale of 1.63621 is the inverse
of K factor, namely 0.027270 gallons per pulse, multiplied by 60 to go from the trans-
mitter’s native rate per second to rate per minute. The multiplier of 1000 changes the units
of volume from gallons to milligallons, as required for three decimal places. If Coordinates
is selected as scaling method, enter 0 for Low In and Low Read. Enter 36670 (milli-
gallons/sec) for High In and +060.000 for High Read (60.000 GPM). Note that Low In and
High In are in converted units after the Multiplier of 1000 to go from gallons to milligallons.
•
Under Analog Out tab, set Range to “4-20mA Current”, Lo Range Reading to +000.000, and
Hi Range Reading to +030.000, both in GPM.