Hach 366 Serie Manual Básico Del Usuario página 26

7.2 External pressure sensor calibration
If the optional external pressure sensor is used, instrument should be calibrated using the ATEX
3660 software, and an in-line certified pressure gauge. The calibration procedure first displays the
External sensor calibration dialog box.
Calibration procedure uses two pressure points. The currently measured barometric pressure,
labeled "First point", is displayed in the field "Measured value". In the First point entry box, enter the
actual pressure (in mbar) and click on Cal1 to store the first calibration point.
Increase the pressure to the pressure sensor and follow the same procedure for the Second point.
Click on Cal2 to store the second point.
• The pressure values for calibration points 1 and 2 must be above 500 mbar
• "Measured value" at point 2 must be at least 20% above the "Measured value" at point 1
• "Calibration value" at point 2 must be at least 20% above the "Calibration value" at point 1
The last field should now display the "Measured value" for the last calibration point. Choose Quit to
close the dialog box and to end this procedure.
7.3 Gas sensor calibration
7.3.1 Selecting the calibration mode
The sensor can be calibrated either in air, in line in the liquid sample, or using a calibration gas.
Select the applicable calibration mode from the instrument keyboard:
Note: The calibration mode can be selected either from the instrument or from the software.
1. Push "MODE" and "CAL" at the same time. The instrument display should show either "Air" for in
air calibration, "Li" for in line calibration, or "SPA" when using a calibration (span) gas.
2. Press either the arrow keys to select mode.
3. Press "STORE" key to confirm. The instrument displays "Sto" for a few seconds, then returns to
measurement mode. Selected calibration mode is stored and is valid until next modification.
7.3.2 Gas sensor calibration range check
When a calibration is performed, the sensor current is compared to the ideal current for the
membrane selected. The variation in sensitivity of the sensor is displayed as a percentage of the
expected value.
Calibration out of bounds
• If the current is not within 60% to 140% of the ideal current, the instrument displays "Er0". This is a
warning message telling that a sensor service is probably needed. The instrument will still calibrate
correctly
• If the current is below 25% or over 175% of the ideal current, the instrument displays "Er1" and the
system will not calibrate. Sensor may require servicing (see the Sensor Manual for details)
Note: This calibration range check can be disabled from the ATEX 3660 software. It is recommended to leave this
check feature enabled. However in specific situations it may be necessary to disable range checking. Contact your
Hach Lange representative before disabling this feature.
7.3.3 "Hold" feature: Avoiding false alarms during calibration
Press the "CAL" key twice, before taking the sensor out of sample to run the "Hold" feature. This
avoids triggering false alarm outputs when the sensor is in the air. The LCD and PC will still display
the actual readings.
Perform the gas sensor calibration as indicated in following paragraphs.
During calibration, the instrument holds the alarm outputs, and flashes a "hld" message alternately
with the measurement. When calibration is done, and sensor is back into sample, press "MEAS" to
quit the "Hold" feature, resuming normal measurements operations.
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