Hach Orbisphere 51 Series User Manual Download

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Calibration menu

8.2

TC gas sensor calibration

Calibration of the measured gas

Start

Before initiating a calibration process, the calibration parameters must be
set by pressing on the

Modify

button. The last calibration parameters are

memorized, so this step can be ignored if the correct parameters are
already set.
Similarly, if only the calibration value has changed, then this can be updated
directly instead of pressing the

Modify

button.

Note:

When calibration is started, a calibration event is set, and the analog

output and relay are put on hold (if selected below) to avoid unwanted alarms
or potential process problems. This resumes when calibration is finished.

Modify calibration
parameters

•

Gas Phase

: Select

liquid

gas

(direct calibration only)

•

Gas unit type

Partial

fraction

dissolved

(dissolved is for

calibration in a liquid only)

•

Gas unit

: The list of available units depends on unit type selected

above.

•

Liquid

: Select as appropriate.

•

Enter the gas concentration according to the value in the calibration
media.

•

Hold during calibration

: On by default, this stops any output from the

instrument during the calibration process to avoid sending invalid
information to any connected device.

•

Automatic calibration stop

: If selected, when the stability criteria is

reached, the calibration process stops automatically.

•

Interferences enabled

: If selected, this takes into account the influence

of interferences during calibration. By default the same interferences as
during measurement are selected.

Press

to start calibration

Calibration results

A calibration screen will be displayed showing current measurement data
which is continually refreshed.
The value “

% ideal current

” is a percentage of the current against the ideal

current for the membrane type selected. If this percentage is not within the
accepted range, an error message is displayed and the calibration process
fails. Refer to

Calibration errors (TC sensors) on page 63

. A warning

message can be displayed when this value is close to the boundaries, but
when calibration can be accepted.
The message is first displayed in the result box. The dialog box with the
error message or the warning is displayed when the finish button is pressed.
The value “

% last calibration

” shows the ratio between the current

measurement and the previous sensor calibration.
The value “

% variation

” indicates the variation during the last 3

measurements, which is the stability of the measurements. A variation as
low as possible is needed for a precise calibration.
The display shows the actual calibration parameters, and the actual
readings (temperature, barometer, current).

Note:

In case of calibration failure, consider replacing the membrane. See

the sensor maintenance manual for details.

Verification

Similar to the calibration procedure, but for verification of the actual
calibration values. The result of the measurements made during the
verification is not stored and the actual calibration data is not modified.