Chapter 3 Operation
FastFlo™ 620S Instruction Manual
3-4
IM-62S
Entering Alarm Parameters
Use the High Alarm and Low Alarm function to set or adjust alarm trip
points. The alarms have a minimum hysteresis of 3% to avoid "chatter-
ing." When setting a window alarm, the alarm setpoints must be at least
twice the hysteresis value apart. We suggest at least a 10% separation
between window alarm setpoints. If you choose not to use the high alarm
for a specific alarm function, Sierra recommends that you set the high
alarm at 100% of the user full scale setting which creates an “over-range”
indicator. Your flow meter will continue to indicate flow and generate a
signal if the flow is over the maximum range, but will not operate within
the specified accuracy.
Entering Alarms with the LCD Display
Enter alarms setpoints directly in engineering units.
1. Select the desired range. Press FUNCTION, enter the password.
Press FUNCTION until
High Alarm
or
Low Alarm
appears on the dis-
play.
2. Use the UP or DOWN arrow keys to enter the high or low alarm set-
point value in engineering units.
3. Press FUNCTION to advance to the next option, or after 12 seconds
of non-activity the meter returns to the Run Mode and the new pa-
rameters are in effect.
Entering Alarms without the LCD Display
When using a DVM to set alarms, the setpoint is a percentage of the flow
meter’s user full scale.
VOLTS = (ALARM PERCENT x 5.0)
If you want to alarm at 25% of user full scale, used in Step 3 below,
press the UP or DOWN button until 1.25 VDC is present on the DVM. If
you want to alarm at 75% of user full scale, press the UP or DOWN but-
ton until 3.75 VDC is present on the DVM.
1. Set the DVM to voltage mode and connect between Vout+ and
Vout– on the flow meter terminal block.
2. Select the desired range. Press the FUNCTION button until a solid “5”
(high alarm) or solid “6” (low alarm) appears on the LED.
3. Adjust the UP or DOWN button until the DVM indicates the desired
setpoint voltage as described above.
4. Press FUNCTION again to advance to the next option, or after 12
seconds of non-activity the meter returns to the Run Mode and the
new alarm parameters are in effect.
Caution!
The flow meter must
not be reporting or
measuring gas flow
during adjustments.
