Hach-Lange ORBISPHERE 3650 - Manual (Page 43)

41
Section 6 Calibrations
6.1 Atmospheric pressure equilibrium
Since the instrument is sealed against moisture, you must open the barometric pressure sensor
relief valve switch on top of the instrument (see
Figure 1 on page 19 for actual location) to
permit the instrument to achieve atmospheric pressure equilibrium, and take an accurate
barometric pressure reading.
This must be done with every calibration. To open the relief valve, depress and hold down the
pressure sensor relief valve switch for five seconds, then release.
6.2 Pressure calibration
If you have access to an accurate barometer, you may wish to calibrate the instrument's internal
barometric pressure sensor. This is done using the PC WinLog97 program. Choose
Troubleshooting
, Pressure Calibration and an informational message will appear to warn you
that the instrument’s current pressure calibration will be lost.
Choose OK to continue. The calibration procedure then displays a Pressure Calibration dialog
box. The Measured Pressure value shows the current instrument pressure reading.
Note: Since the instrument is sealed against moisture, you must open the barometric pressure sensor relief
valve switch (location depicted in Figure 1 on page 19 ) to permit the instrument to achieve atmospheric
pressure equilibrium, and take an accurate barometric pressure reading.
Enter the current atmospheric pressure, in mbars, in the Calibration Pressure entry box.
Choose Calibrate to direct the instrument to read and display the Measured Pressure using
this calibration value.
Choose Quit when you are satisfied with the pressure calibration to return to normal operation.
6.3 Calibration range checking
When calibrating the sensor in air or in a span gas, as detailed in Sensor calibration below, the
new calibration current should be between 25% to 175% of the ideal current (which is stored in
the instrument's non-volatile memory for each membrane). If not, the instrument displays Err on
its LCD and the system will not calibrate. When the system will not calibrate, it is likely that a
sensor service will be required.
See also Troubleshooting on page 45 , if you suspect any problems with the analyzer.
Note: This calibration range checking can be enabled or disabled using the WinLog97 program (see Sensor
calibration range checking on page 39 ). It is recommended to leave this checking feature enabled. In
special measurement situations it may be necessary to disable range checking. This will allow calibration
between 0% to 999% of the ideal current. Contact a Hach Lange representative before disabling this range
checking feature.