Metek 920, Operator'S Manual With Essential Health And Safety Requirements

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3-46 | Model 920 Multi-Gas Analyzer
3. Record these signals in a log book every month.
It is important to record these values during a Manual Zero to
simulate the same conditions as during the original recordings. If the
values are recorded using the sample gas, the results may be skewed
because the composition of the gas can vary. All signals should return
to within 5 % of the values recorded the previous month.
Recording Initial Sample Response Time
The analyzer’s sample response time can be used for two functions:
• To help you set the sample gas flow rate.
• To help you determine if the typical response time is increasing, which
can indicate a plug in the sample system.
Typically, a good response time is approximately 30 seconds when the
sample system is clean and operating at peak efficiency (may vary due to
Sample Line length).
To check and record the initial sample response time:
1. Manually Zero the analyzer.
2. After the Zero is complete, view the RUN mode normal display
and observe the output concentration changes. Observe and record
the time it takes the analyzer to display the first reading after the
analyzer’s
Flow Control setting is switched from Continuous Zero
Gas mode – either “ 10 ” ( probe tip ) or “1 10 ” ( manual ) – to Analyzer
Control (“ 0 ”).
It is important to record the response time only after performing a
Manual Zero to simulate the same conditions during the original
recordings.
3. If the sample response time is adequate (first reading after a Zero and
after changing the Flow Control mode from “ 1 ” to “ 0 ” is approximate-
ly 30 seconds), no further adjustment is necessary.
The sample response time may vary, depending on Sample Line
length.
4. Record these signals in a log book every month.

NOTE

NOTE

See “Manually Zeroing
the Analyzer” in this chapter.

NOTE