Apogee MO-200 Series User manual

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Oxygen Meter
This sensor is a galvanic cell-type oxygen sensor that
measures oxygen gas (O2) in air. It has a lead anode, a gold
cathode, an acid electrolyte, and a uorine resin membrane.
The current ow between the electrodes is proportional to
the oxygen concentration being measure. An internal bridge
resistor is used to provide an mV output linearly proportional
to O2. Unlike polargraphic oxygen sensors, galvanic cells do not
require a power supply. The hand-held meter used to measure
the sensor uses a 3 V coin cell battery.
The mV output responds to the partial pressure of oxygen in
air. The standard units for partial pressure are kPa. However,
gas sensors that respond to partial pressures are typically
calibrated to read out in mole fraction of the gas in air, or units
of moles of oxygen per mole of air. These units can be directly
converted to % O2in air, or ppm O2in air. The concentration
of oxygen in our atmosphere is 20.95%, and this precise
percentage has not changed for decades. It is also constant
across changing temperatures or pressures. This allows for
precise calibration of the instrument.
Being a galvanic cell type sensor, a small amount of oxygen
is consumed in the reaction in order to produce the current
ow and subsequent mV output. The oxygen consumption
was measured to be 2.2 µmol O2 per day when the O2
concentration was 20.95% (3240 mmol) at 23 C.
Humidity Changes
The graph below shows an example of humidity dependency.
The sensor chemistry is not inuenced by humidity, but its
output decreases because O2 is displaced by water vapor
molecules in the air. The effect of humidity is larger at warmer
temperatures because there is more water vapor in the air. To
eliminate humidity effects, simply recalibrate.
For use in high humidity, such as soil, remove
the head and take the calibration measurement
over water in a sealed container as shown at
right.
Oxygen Meter
MO-200 Series
Effects on Output
For the most reliable measurements, the O2sensor is designed
to be used in a vertical position, as shown. A ow-through or
diffusion head is not required for making measurements.
Inuences from Various Gases
The sensor is unaffected by CO, CO2, NO, NO2, H2S, H2, and
CH4. There is a small effect (approximately 1%) from NH3, HCI,
and C6H6 (benzene). The sensor is sensitive to SO2 and can be
damaged by O3.

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(SMPL)
99 Sample
Measurements
(LOG)
99 Log
Measurements
(LOG)
99 Daily Averages
Measurements
Viewable on meter LCD & downloadable Downloadable Only
Cleaning
Debris on the meter is a common cause of low readings. Salt
deposits can accumulate on a sensor from evaporation of
sprinkler irrigation water and dust, which can accumulate
during periods of low rainfall. Salt deposits should be dissolved
and removed with vinegar and a soft cloth or q-tip. Dust and
other organic deposits are best removed with water, rubbing
alcohol or window cleaner.
Temperature Sensitivity
A change in temperature changes the amount of O2 available
to the sensor and therefore changes the mV output that
correlates to the atmospheric constant of 20.95%. Additionally,
the sensor electronics have a small temperature dependence.
To eliminate temperature effects, simply recalibrate.
Pressure Sensitivity
A change in barometric pressure changes the amount of O2
available to the sensor and therefore changes the mV output
that correlates to the atmospheric constant of 20.95%. To
eliminate pressure effects, simply recalibrate.
Using the Meter
1) Press the power button to start. The meter
will turn itself off two minutes after button is
pushed to conserve battery.
2) To calibrate sensor: While sensor is in
open air, press mode twice (RUN should be
blinking), then while pressing sample, press
mode once. Screen will display CAL during
calibration. Calibration can be done in either
SMPL or LOG mode. Recalibration should be done
when signicant changes in pressure, humidity,
or temperature occur. See page 3 for further
information about these effects on output. See
page 10 for life expectancy.
3) To choose mode: To choose
between SMPL and LOG modes
push mode once and use the up and down
arrows to make choice. Once desired mode is
blinking press mode two more times to begin.
4) For automatic measurements: Use LOG mode
(use step 3 to choose LOG mode). Meter will
power on and off to record a measurement every
thirty seconds.
NOTE: O2Meter units are % concentration.
5) For manual measurements: Use SMPL mode (use step 3 to
choose SMPL mode). Press sample when you want to take a
measurement. Store up to 99 manual measurements. When
99 measurements are taken in SMPL mode, no more SMPL
measurements can be stored.
6) To reset meter: From LOG or SMPL mode, press mode twice
(RUN should be blinking), then while pressing down, press
mode once. CAUTION, this will erase ALL measurements.
7) To review data: Press up/down. To exit and return to
present conditions and the capability to take measurements
press sample.
8) In LOG mode, every 30 minutes it will average the 60
30-second measurements taken and store the average. 99
30-minute averaged measurements can be stored. Every
48 measurements (making a 24 hour period) the meter will
also store a daily average. In addition, 99 daily averages
can be stored and are available for download only, these
measurements are not viewable on the meter LCD. All
measurements taken in LOG mode will continue to be stored,
eliminating the oldest measurement. To keep data, switch out
of log mode.

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Error Codes
The most common error code is Error 4. The meter will display
this error code on the screen if the battery voltage is too low.
To replace the battery, unscrew the back area on the meter.
Then use a pair of tweezers to gently remove the battery and
replace it with a new one. Screw the back cover back on the
meter, but be careful not to over-tighten as it can affect the
LCD screen.
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Memory
• 99 manually stored data
points
• Automatically store 99
consecutive 30 minute
averages
• 99 daily averages
Diffusion Head
• 3.5 cm tall; 3.5 cm diameter
• 125 mesh screen
• Creates air pocket
Flow-Through Head
• 3.2 cm long by 3.2 cm
diameter
• 1/8" barbed adapters
• For hose connections
Mass
• Meter: 80 g
• Sensor and wire: 175 g
Range
• 5 to 100% O2
Response Time
• 14 seconds
Stability
• ± 0.1% O2 under stable
atmospheric conditions
Repeatability
• ± 0.1% O2
Specications
Input Power
• CR2320 3 V coin cell battery
Operating Environment
• 0 to 50 C
• < 90% non-condensing
relative humidity up to 30 C
• < 70% relative humidity from
30 to 60 C
• 60 to 150 kPa
Display
• 4.2 by 2.8 cm
Meter Dimensions
• 11.8 by 5.9 by 1.4 cm
Gas Effect
• CO2, CO, NO, NO2, H2S, H2,
CH4- No effect
• NH3, HCI, C6H6 (Benzene) -
<1%
Cable
• 2 meters of shielded, twisted-
pair wire
• Foil shield
• Santoprene jacket
• Longer cable lengths are
available in multiples of 5
meters
Warranty
• 1 year against defects in
materials and workmanship
www.apogeeinstruments.com
[email protected]
435.792.4700
Fax: [phone]
Characteristics
Zero Offset
The mV output in ultra-pure nitrogen gas (0.000% O2)
is typically 2% of the output in 20.95% O2. Precise
measurements of hypoxic and anaerobic conditions can be
made by making a periodic zero calibration of the sensor with
ultra-pure nitrogen gas.
Life Expectancy
The life expectancy of the sensor is expressed in %-follows:
[Oxygen Concentration (%) x Exposure Time (hours)]
Accordingly, the life of an Apogee oxygen sensor is 900,000
hours or approximately 5 years of continuous use at 20.95%
oxygen at 20 C.
Storage Temperature
The life of the sensor can be extended by storage at a lower
temperature. For example, a sensor stored at 0 C will have a
life expectancy approximately twice that of a sensor stored
at 20 C. Below -20 C the electrolyte will freeze. This does
not damage the sensor, but to resume measurement the
electrolyte must be thawed. Maximum storage temperature is
60 C.
Shock and Vibration
The sensor is resistant up to 2.7 G of shock. However, vibration
may influence the sensitivity of the sensor and should be
minimized.