Envent 331S - Dual Sensor Analysis cycle (SDS)

Envent Engineering Ltd. Page 11 Revision 2.4
The first part of the RRA Analysis (2) to (3) completes when the mV value drops 100
mV. Once it drops 100 mV, stage (3) to (4) "Concentration Calculation" starts.
On this stage, the H
2
S slope is optimal for calculating the final H
2
S value for that
Cycle. Algorithms are used by the controller board to calculate as accurately as
possible the H
2
S final value. Once the final value is obtained, it will stay at that value
(shown in the display and 4-20 mA analog outputs) until the next cycle has finished
and updates the H
2
S current reading. This stage will always be 1/5 of the amount of
time it takes stage (2) to (3) to complete. Thus, if stage (2) to (3) took 600 seconds,
then stage (3) to (4) will take 120 seconds.
It is important that the analyzer is used for its calibrated H
2
S range. Do not use this
unit for an application that will require readings outside of its calibrated range. This will
cause the H
2
S sensing tape to run out faster and may cause less accurate readings.
The range is determined by the aperture strip in the sample chamber. For more
information analyzer ranges, refer to "Aperture Strip" on page 19.
Dual Sensor Analysis cycle (SDS):
Dual sensor analyzers have two sensors that read H
2
S from two different samples at
the same time, e.g. Sensor 1: 0-20 ppm H
2
S Sensor 2: 0-200 ppm H
2
S. The analysis
cycle process is the same per sensor as explained earlier in this section; however,
some extra algorithms have been implementing to help with the interaction between
the two sensors and their analysis cycles' timing.
Both analysis cycles for each sensor will always start at the same time. When the
motor moves and new H
2
S sensing tape area is exposed, a new analysis cycle has
started for both sensors. However, the analysis cycles from each sensor will finish at
different times. Either sensor 1 or sensor 2 will finish its analysis cycle first.
Regardless of which sensor finishes first, it will wait for the other sensor to complete
its analysis cycle. Once both sensors have completed their analysis cycles, the motor
will move and new H2S sensing tape area is exposed for a new analysis cycle.
It is important to clarify that when the first sensor has finished its analysis cycle, even
when it is waiting for the second sensor to complete its analysis cycle, it immediately
updates any outputs associated with that sensor (Analog output 4-20 mA, alarms,
display H2S value, etc.).