Non-Latching Alarm Option; Remote Trigger Option; Modification For Diisocyanate Monitoring In High Humidities - Honeywell SPM Technical Handbook

15 m
61 cm

5.12 Non-latching Alarm Option

The non-latching alarm option will automatically reset
any gas alarm when the current concentration has
dropped below the Alarm Level 1 set point. The SPM
will not reset or modify any alarm indication while the
detected gas concentration is at or above the Alarm
Level 1 set point.

5.13 Remote Trigger Option

The Remote Trigger option will control the instrument's
monitoring. Normally, Model SPM is a continuous-
monitor instrument. The Remote Trigger option allows
the SPM to monitor on command.
The SPM waits for a remote signal. When triggered, the
SPM monitors for one sample period. At the end of the
sample period, the instrument posts the results based
on the calculated gas concentration (display, 4-20 mA,
etc.). The SPM then looks for the next remote trigger.
If at the end of the sample period there is no remote
trigger, the SPM pauses to await another trigger. When
a trigger is sent, the SPM sets the 4-20 mA output to 4
mA, and shows (SAMPLING) on the display.
SPM Technical Handbook
15 m
SPM
SPM Single Point Monitor
If at the end of the sample period there is another remote
trigger request, the SPM shows the concentration of the
completed sample and begins another sample period.
The 4-20 mA output reflects the value of the last gas
sample.
5.14 Modification for Diisocyanate
Monitoring in High Humidities
At high relative humidities (>85% RH), moisture build-up
can occur in the optics of the monitor and subsequently
dampen the detection tape. The Diisocyanates
Chemcassette , normally yellow, becomes transparent
®
when dampened. This transparency is viewed by the
monitor's optics and can result in low but false ppb
readings in moist air, even though the typical reddish-
pink reaction stain will be absent.
An optional optics modification to accommodate this
moisture effect is available through Honeywell Analytics'
Service Department. It consists of a white, porous frit
which is fitted in the nose-piece behind the Chemcassette
and optics block. With this modification, the optics no
longer "see" through a moist tape, and false positives
are eliminated. Because the frit is porous, proper flow
rates are still maintained, as are accurate repeatable
readings in the presence of diisocyanates.
Caution
SPM units will not detect gas if no tape is present.
Therefore, you must be aware of the amount of
tape on the supply reel(s).
An end of tape condition will no longer be detectable by
the modified optics since the frit simulates the presence
of tape in the optics even when no tape is present. Since
there is no end-of-tape fault, you must be aware of the
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