Inputs And Outputs - Sentry Sample Sequencer 6 Installation, Operation & Maintenance Manual

 NOTE
See Appendix C on page 37 for interface protocols and wiring for a number of typical analyzers . If using the Sample
Sequencer 6 with a Hach analyzer, see Appendix B on page 33 .

Inputs and Outputs

A variety of inputs and outputs are available on the Sample Sequencer 6. The Sample Sequencer 6 is a modular
design utilizing dedicated IO boards. Up to two IO boards can be fitted into each enclosure. Up to eight IO boards
can be equipped with one Sample Sequencer 6. This solution would utilize 4 enclosures, one with the CPU and
communication board and 3 IO extender enclosures. In general one IO board corresponds to one four output manifold.
Analog Inputs
ƒ Up to two analog inputs are located in the sequencer enclosure for reading 4–20 mA signals from up to two different
analyzers.
ƒ The sequencer converts 4–20 mA signals into engineering units for display, and outputs the same signals for the
track and hold analog outputs.
Analyzer Alarm Inputs
ƒ Alarm inputs are typically used to indicate a loss of sample flow to the analyzer.
ƒ Two analyzer alarm inputs are located in the sequencer enclosure.
ƒ Alarm inputs cause the digital alarm output for that sequencer to be set.
ƒ In Continuous mode:
1. An alarm immediately closes the active sample valve and opens the next sample valve.
2. The next sample valve remains open until one of the following occurs:
a. the alarm clears
b. one minute elapses
c. the timer expires
3. After the sample valve closes, the sequencer opens the next sample valve.
4. The sequencer continues trying to establish flow until the analyzer alarm clears.
ƒ In Batch mode:
1. An alarm starts a timeout timer. (The operator can adjust the timeout timer for all samples simultaneously by
setting the sample timer.)
2. If the sequencer does not receive an end-of-batch indication from the analyzer, or if the alarm does not clear
before the timer expires, the sequencer closes the current sample valve and opens the next valve in the
sequence.
3. If the end-of-batch indication is received before the timer expires, the sequencer assumes the alarm is not a loss
of flow and continues with normal operation.
Sentry Sample Sequencer 6 Controller 9