Microcontroller; Loop Driver - Hoffer Flow Controls CAT1 User Manual

8 Principle of Operation
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
FM
CF
Where:
AF
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.
HP-310
flowrate
is either the Average K-Factor or the Linearized K-Factor
from the Frequency / K-Factor table.
= 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.
= Is the Correction Factor setting.

current
= Is the 20 mA maximum Flow rate value.
frequency

Kfactor



4 mA 16 mAx

FM
x 60 xCF

flowrate


AF