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Sample Sequencer
Operation
minute or more for stream switching. The analyzer analog output signal is ignored during
the delay time. The necessary delay depends on the valve manifold design, sample line
length from the manifold arrangement, sample velocity, analyzer response time, sample
constituents and differences between the amount of constituents for each sample point.
When switching sensors, the sensor signals are usually recognized quickly by an analyzer
and the delay time should be set accordingly, i.e., approximately 1-2 seconds.
DWELL Time
is the time period during which a valid analyzer signal is switched through the
Sample Sequencer during which time Sequencer alarms are commutated. The dwell time
required will depend on the destination device such as a data logger, computer, recorder,
etc., for both the analog data and the alarm output. The output signal must be valid for this
whole DWELL time.
For instance, if output is to an eight point recorder with a print-out cycle time of 3 seconds
per point, a minimum of 24 seconds plus would be the minimum DWELL time. Connecting
to a computer system could have a minimum DWELL time requirement of 3 to 5 seconds or
more. The only penalty for long dwell time is it may increase the cycle time and decrease
responsiveness.
The DWELL time can be left on until the next on sample begins to modify the result as
shown in Figure 8.
Alarms are evaluated only during the DWELL time.
The DELAY time and DWELL time must be at least one second less than the CYCLE time.
SENTRY Equipment Corp • P. O. Box 127 • Oconomowoc, WI 53066 • 262/567-7256 • FAX: 262/567-4523
Web: www.sentry-equip.com • e-mail: sales@sentry-equip.com
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