Hoffer Flow Controls CAT1 Series, Руководство пользователя

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8 Principle of Operation
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AF
flowrate
mAx mA current 16 4
3-1-2 Microcontroller
The Microcontroller, located on PCA183, accepts the square-wave
output of the preamplifier and performs all of the calculations that
are required to control the Loop Driver. After measuring the
frequency of the square-wave, the Microcontroller uses the
following equations to compute the flow rate and current.
Where:
Kfactor = Is dependent on the Flow Calculation Method setting and
is either the Average K-Factor or the Linearized K-Factor
from the Frequency / K-Factor table.
FM = Is the Flow rate Units setting of 0, 1, or 2. Where “0” is
for Seconds, “1” is for Minutes, and “2” is for Hours.
CF = Is the Correction Factor setting.
Where:
AF = Is the 20 mA maximum Flow rate value.
If the calculated flowrate is greater than the AF setting, the current
will be set to 24mA to indicate an “Over-range” condition. After
calculating the current, the Microcontroller digitally sends the
current information to the Loop Driver.
3-1-3 Loop Driver
The loop driver, located on PCA183, uses the digital information
sent to it by the Microcontroller to set the current of the loop. The
Loop Driver also supplies power to the Microcontroller.
3-1-4 Communications Interface
The Communications Interface, located on PCA183, provides an
RS232C port to the Microcontroller. The connector for the
communication interface may be accessed by removing the top
plate. The external terminal device provides power for the
Communication Interface. The Communications Interface is used
to configure and trouble-shoot the transmitter.
xCF x
Kfactor
frequency
flowrate
FM
60
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