LaMotte DO 4000 Dissolved Oxygen Meter - Manual (Page 11)

CALIBRATION
The DO 4000 should be recalibrated daily using one of the following
methods to account for changing environmental conditions. For most
accurate results, calibrate as close to the temperature of the sample to be
tested as possible. DO NOT CALIBRATE WITH THE SHEATH
ON.
The saturated air calibration is easiest and generally considered to be a
very accurate and reliable procedure. Alternative methods are listed on
pages 12-16.
NOTE: If the DO 4000 has not been set on the constant polarization
mode, set constant polarization button to out position on top of meter
and wait 15 minutes before calibrating.
SATURATED AIR (RECOMMENDED PROCEDURE)
NOTE: It is very important that the membrane be completely dry
before starting air calibration. Vigorously shake the probe several times
to remove water droplets from the membrane. However, calibration
must be done in humid not dry air!
1. Hold the probe several inches above water surface.
2. Set “SALINITY COMP” knob to 0. Press “%SAT” button to turn
the meter on. Wait for display to stabilize.
3. Adjust the “SLOPE” control until display reads 100. The meter is
now calibrated for use. Turn off constant polarization unless meter is
to be used again shortly.
NOTE: If readings are erratic, or the meter can not be calibrated
see Troubleshooting on page 18.
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