LaMotte DO 4000 Dissolved Oxygen Meter - Manual (Page 10)

INITIAL/REPLACEMENT PROBE CALIBRATION
A precalibration procedure must be performed on a new meter and
probe or each time a new probe is attached to the meter. After the
precalibration procedure has been performed, the meter should be
calibrated following one of the calibration procedures on pages 11-14.
1. Assemble probe.
2. Attach the probe to the meter with the arrow on the connector
facing upward.
3. Set the salinity and slope knob to zero. Set the constant polarization
button to the out position. Wait 30 minutes.
4. Place the probe several inches above a container of water. The probe
must be calibrated in humid, not dry, air.
5. Press the "% SAT" button. Adjust the slope knob until the display
reads 100%. If the slope knob is between -1 to 1, the meter is ready
to use. Proceed to the section in the manual on testing.
6. If the slope knob is not within -1 to 1 range, set the slope knob back
to zero and continue with Steps 7-10.
7. For meters with serial numbers 375 or higher (meter case has two
holes on the side to access potentiometers), remove hole plug from
the Slope Adjustment Pot.
For meters with serial numbers 0-374 (meter case has one hole on
the side), remove the 4 screws and remove the case.
8. Turn the meter so that is aligned like the diagram on page 15. The
potentiometer, on the circuit board, closest to the probe jack at the
bottom of the meter, is the Slope Adjustment Potentiometer. Be sure
to identify the correct potentiometer before making any adjustments.
9. Adjust the Slope Adjustment Potentiometer with a slotted screw
driver (1/8” or smaller) until the meter reads approximately 100%.
10. Replace the hole plug or case. Use the slope knob to set the meter
display to exactly 100%. The meter is now ready to use. Proceed to
the CALIBRATION section.
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