Hoffer Flow Controls CAT3-DC-MIL User Manual page 16

8 Operation
4-3 Analog Output
CAT3-DC-MIL provides an analog output current that is proportional to the
flow rate. The analog output is scaled as follows:
4 mA = 0 GPM
20mA = Max Flow Rate in GPM
If the calculated flowrate is greater than the 20mA setting, the current is set
to 24mA to indicate an "Over-range" condition. Microcontroller calculates
the current and sends data to the Loop Driver. The Loop Driver, located on
PCA183 controls the current of the loop. The Loop Driver also supplies
power to the Microcontroller.
The analog output is updated 8 times per second (8 Hz). When flow stops,
the time for the analog output to return to 4 mA is between 250 mS and 8
seconds, depending on the Maximum Sample Time (MST) setting. MST is
a value between 1 and 80, with each count equal to 1/10
MST setting adjusts the amount of time the electronics will wait for the next
input pulse before returning to zero. This will prevent the displayed flow
rate and/or analog output from going to 0 when the input frequency is less
than the update time of the electronics.
recommended for low flow applications where the minimum input
frequency is below 10 Hz. The default MST setting is 1.
HP-324-5
Flowrate = frequency/K-factor x 60
Where:
K-factor = Is the flow meter calibration factor in
pulses/gal
Flowrate is in gal/min.
Frequency is in Hertz.
th
of a second. The
Adjusting the MST is only