Hach-Lange SIGMA SD900 Refrigerated Sampler and All Weather Refrigerated Sampler User Manual - Manual (Page 70)

68
Advanced sampling
5.3.3.1 Setpoint sampling with an SDI-12 device
When an SDI-12 device is connected to the SD900, its
measurements are available as setpoint sampling triggers (in
addition to the external inhibit.). A maximum of 2 measurement
triggers can be enabled independent of the external trigger. If
multiple triggers are enabled, the program will be activated when at
least one trigger is satisfied, and deactivated when all triggers are
cleared.
To enable measurement setpoint triggers, from the main menu
select
PROGRAM SETUP>MODIFY SELECTED>ADV
SAMPLING>SETPT SAMPLE>SETPT TRIGGER.
If an SDI-12 device is detected, a list of available measurements is
displayed along with the external trigger. Select a trigger source
from the list to define a setpoint.
Note: A check mark in the left most column indicates a specific channel is
already enabled as a trigger. In order to disable Setpoint Sampling, each
individual channel must be disabled.
Each measurement trigger can be defined as a high or low setpoint.
Additionally, an optional deadband value can be set. A deadband
prevents the trigger from rapidly changing between active and
inactive states when the trigger measurement value hovers near
the defined setpoint.
In figures 22 and 23, pH is the measurement parameter selected as
the trigger. The setpoint is set at 7.00 and the deadband value is set
to 0.10 pH.
In a HIGH SETPOINT condition ( Figure 30 ), the trigger becomes
active when the rising pH value reaches the setpoint value of 7.00.
The trigger condition does not clear until the pH measurement
value falls below 6.9 (the setpoint value minus the deadband
value.)
Figure 30 High Setpoint
1 pH values scale 4 Deadband
2 Setpoint trigger ON (Time-stamp recorded in event log) 5 Setpoint (7.00)
3 Setpoint trigger OFF (Time-stamp recorded in event log) 6 Scan intervals