Loop Driver; Pulse And Alarm Output - Hoffer Flow Controls HIT-2A User Manual

square-wave, the Microcontroller uses the following equations to
compute the flow rate and current.
flowrate
Where:
Kfactor = Is dependent on the Flow Calculation Method setting
FM
CF
current
Where:
AF
If the calculated flowrate is greater than the AF setting, the
current will be set to 24mA to signal an "Over-range" condition.
After calculating the current, the Microcontroller digitally sends
the current information to the Loop Driver.
3-1-4

Loop Driver

The loop driver uses the digital information received from the
Microcontroller to set the current of the loop. The Loop Driver
supplies power to both the Preamplifier and Microcontroller.
3-1-5

Pulse and Alarm Output

The Pulse and Alarm outputs are two optically isolated open
collector outputs. The alarm output activates when the total flow
or the rate reaches a user defined level. The pulse output activates
to give a scaled pulse output indicative of the total flow. Both of
these outputs are rated for 100 VDC at 100 mA.
frequency

Kfactor
and 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, 2 or 3. Where "0" is
for Seconds, "1" is for Minutes, "2" is for Hours and "3"
is for days.
= Is the Correction Factor setting.
 4
mA
= is the 20 mA maximum Flow Rate value.
Theory of Operation
60
FM
x

flowrate
 16

mAx

xCF



AF
HP-306
8