Sentry Equipment Corp | Sample Sequencer
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SPD 5.5.15 35
5.3 Operating Modes
5.3.1 Continuous Mode
This mode is for continuous output analyzers such as sodium, conductivity, pH, O
2
, some
colorimetric, and many others.
Timing Considerations for the Continuous Mode
Figure 36 illustrates the timing diagram for the continuous mode. The following considerations
should be made when determining the timing for your system.
Analyzer Alarm: An analyzer alarm will immediately close the active sample valve and open
the next sample valve. That sample valve will remain open until the analyzer alarm clears or
one minute elapses. After one minute, the Sample Sequencer will open the next sample
valve. The Sample Sequencer will continue trying to establish flow every minute until the
analyzer alarm clears.
Calibration Hold: A calibration hold signal will cause the Sample Sequencer to wait at the
active sample with the valve open. Once the calibration indication clears, the Sample
Sequencer will resume operation entering the Flush state for the sample that was active
before the calibration hold indication was received.
Flush Time: After switching to a successive stream, there will be a settling time for the
analyzer to stabilize to the new sample. The analyzer analog output signal is ignored during
this time. The necessary Flush time depends on the valve manifold design, sample line
length from the manifold arrangement, sample velocity and analyzer response time.
Sample Time: Sample Time is the time period during which a valid analyzer signal is read.
Analog outputs are updated and point identification relay contacts are closed during this
time. The necessary Sample time should be set long enough to recognize stable readings
and to provide recording devices time to capture the data.
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