Sierra FLAT-TRAKTM 780S - Manual (Page 31)

Series 780S Instruction Manual Chapter 3 Operation
IM-78S-B 3-5
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
"chattering." 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 using the LCD Display
Enter alarms setpoints directly in engineering units.
1. Select the desired range. Select FUNCTION, enter the pass-
word. Select FUNCTION again until High Alarm or Low Alarm
appears on the display.
2. Use UP or DOWN to enter the high or low alarm setpoint value
in engineering units.
3. Select FUNCTION to advance to the next option, or after 12
seconds of non-activity the meter returns to the Run Mode and
the new parameters are in effect.
Entering Alarms using the Single-Digit LED
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 button 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 de-
sired 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.