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Geotechnical Instruments
CODAOM002 Iss.06
3
Advanced Features
3.1 Main
Menu
The main menu is pass-code protected to prevent access to the advanced features by un-trained
operators.
After pressing key 1-Menu from the main gas screen the analyser will prompt for a pass-code. Enter
‘0102’ and press key ‘0’ to confirm. If entered correctly the main menu will be displayed otherwise you will
be returned to the main gas screen. To exit this screen press key ‘0’. From the main menu you can select
from the following four options :-
1-Calibration
2-Alarm Settings
3-Battery
4-Data Logging
3.2 Calibration
The Geotechnical Instruments range of Gas Analysers are calibrated during manufacture and when
returned for service. However, to improve accuracy between services a user / field calibration can be
performed. This section sets out the correct procedures to achieve an accuracy user calibration. If this
calibration is completed incorrectly it may decrease the accuracy of the Gas Analyser.
Two important terms that are used within this section are “Zero” and “Span”.
Zero: The point at which the Gas Analyser is calibrated when there is none of the target gas present.
Span: The point at which the Gas Analyser is calibrated when a known quantity of the target gas is
present.
Prior to making a measurement, to achieve optimum performance, it is recommended that the zero and
span is checked.
It is recommended that a zero and span is performed on first receipt of the instrument
On receipt of the instrument, or when the instrument has not been used for some time, a zero and span
calibration
should not
be carried out until the VOC sensor has normalised. The instrument should be on
for a minimum of 1hour before calibration.
3.2.1 Zeroing
The Diveair analyser can be zeroed by using VOC free Nitrogen gas. All channels will be zeroed at the
same time. The instrument should be switched ON and fully warmed-up. If the instrument is still in it’s
warm-up phase with stars on the main reading screen the instrument will not allow calibration.
A flow adjuster will be required to set the flow to 300 ml/min.
1
Turn on the gas cylinder and adjust the flow.
2
If required, connect the exhaust port of the analyser to a suitable discharge point.
3
Connect the gas cylinder and flow adapter to the inlet port of the analyser.
4
Allow the gas to flow for 3 minutes.
5
While in the read screen check that the readings have stabilised
6
From the calibration menu Press key ‘1-Zero channels’. A brief warning screen is displayed
advising caution. Press key ‘1’ to acknowledge the caution and continue the calibration.
7
The message “Please wait...” is displayed while the instrument completes the calculations.
When complete a summary screen will be shown that displays the status for each channel
either okay or FAILED! There are a number of reasons for a particular channel to fail to zero
(see troubleshooting).
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Turn off the gas and remove the hoses when finished.