101
Communication setup
8.4.2.2 Set Point alarms
Set Point Alarms look for trip points to be reached (either high or low or both) before
initiating an action. For example an initiated action may be the closing of a relay when the
water level exceeds 60 cm (24 in.) or drops below 10 cm (4 in.). Set Point Alarms activate
when a user-definable high and/or low set point is reached.
1.
Enable one of the alarm conditions.
2.
Select an action to occur when the alarm is activated.
3.
Set either a High trip point or a Low trip point.
4.
After entering the trip point enter the deadband value.
Note: Log rainfall to use an alarm on a rainfall condition; likewise, log flow in order to implement and
alarm on a flow rate of change.
Set point alarm conditions:
Note: Rainfall and Flow Rate of Change alarms are HIGH set point conditions; they take no
deadband and they are time dependant.
Deadband
After entering the trip point, enter a deadband value. The deadband is the area between
alarm “turn-on” and “turn-off”.
The purpose of setting the deadband is to eliminate alarm chatter which may occur if the
“turn-on” and “turn-off” values are too close together. Small fluctuations occurring when
the reading is at or near the trip point can rapidly toggle an alarm relay on and off.
In the low setpoint example shown below, the deadband is set to 0.10 pH. When the pH
drops to 7.0 (lower solid line), the alarm trips, but the alarm does not turn off until the pH
comes back up to 7.10 (
). This difference is the deadband setting which should
be set according to the characteristics of the item being measured.
•
Level
•
Cabinet Temperature
(refrigerated samplers)
•
Flow
•
Analog Channels 1–3
•
Flow Rate of Change
•
Analog Ch. 4 or D.O.
•
pH
•
Analog Ch. 5 or D.O. Temp.
•
ORP
•
Analog Ch. 6 or Conductivity
•
Process Temperature
•
Analog Ch. 7 or Conductivity Temp.
•
Rainfall
Goodnal STP ST041 Pre Treatment (Sigma 900 MAX All Weather Refrigerated Sampler) Vendor Manual
Q-Pulse Id VM373
Active 29/10/2013
Page 101 of 122
