10 3600 Analyzer for O
2
Measurement—Operator’s Manual
3600O2.OM.E9903
1.3.2 Oxygen Measurement
Typical 3600 instruments are delivered with the appropriate measurement and
membrane selections pre-set for your application. However, you can change these
settings if desired. Instructions for the various “options” included are found in
section 1.4, the Modify Options Menu.
The simplest way to check if your system is pre-set for the right measurement
units is to place the system in oxygen measurement mode. Switch on the
instrument (if necessary) to bring up the “Measurement” mode (or select it from
the “Measure Options Calibrate” menu by using the yellow “ñ” or “ò” key if
necessary). You should see a screen like this.
O2 = 00.00 xxx 3
T = 00.0° x ∞
(Note that your system will display actual numerical values in place of the zeros,
and units of measurements for the “x’s” shown here.) If the unit of measurement
on the top line is as expected—for example, in parts per million expressed as
“ppm”—and the appropriate temperature measurement value is expressed (°C,
°K, or °F), then you should be ready to begin to make measurements by placing
your sensor in the sample. (The infinity symbol “∞” only appears as shown when
the system is “busy”, that is, occupied with an internal operation for a few
seconds. Keyboard input will not be accepted during these interruptions.)
Range indication
The range indication appears at the rightmost position of the display’s top line. If
the last position in this line is blank, then you are operating in autoranging mode.
Otherwise, a single digit from 1 to 5 appears, to show which fixed range the
instrument is in. Pressing the “ñ” key will scan this digit upward (“ò” goes
downward) through the permitted “number of ranges” (see section 1.4.1), until it
goes blank, to show that the autoranging mode has been reached. You will also see
the “resolution” of the displayed concentration changing. For example, if you are
configured for three ranges, then you can scan upward through the sequence
...blank-1-2-3-blank... etc. You may see the following message on one or more
fixed ranges (shown here as “Range 3”) during this sequence:
OVERRANGE
RANGE 3
This means that the measured oxygen concentration exceeds the upper limits of
these ranges. Normal corrective action is to press the “ñ” key to reach a less
sensitive range, of which the upper limit exceeds the measured oxygen
concentration. Note that you may see an “Overrange Range 0” message as well.
This is an indication that you are measuring outside the normal limits while in
autoranging mode.
Before making measurements, you should familiarize yourself with the “Modify
Options” menus described in section 1.4. While your instrument is pre-set with
certain default values to anticipate your measurement conditions (for example,
number of ranges, dissolved vs. partial pressure), you may change these for your
application.
What to expect during oxygen measurement
Any sensor previously exposed to the air (or to air-saturated liquid) will, once
placed in a typical sample, generate a signal that decays rapidly at first, then more
slowly as it approaches the actual oxygen level.
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