Teledyne 4020 – Hydrocarbon analyzer (special version for automatic background gas switching) - Manual (Page 83)

Total Hydrocarbon Analyzer Operation
Teledyne Analytical Instruments 65
4.7.2.2 A UTOMATIC B ACKGROUND G AS S ELECTION
For automatic background gas selection:
<▲▼> From the MAIN MENU, scroll to the BACKGROUND
GAS function using the UP/DOWN keys.
<Enter> Pressing activates the function and takes you to
the next screen.
<▲▼> Use the UP/DOWN keys to toggle between the options
until Auto is displayed.
Note: The currently selected background gas is displayed in
parenthesis next to
Auto.
<Enter> Use the key to place the instrument in Auto
mode where the 4020 will automatically use the
background sample/gas as determined from the remote
zero contacts. Note that the AL-2 contacts will switch
accordingly. See Section 4.7.2.3 Match/Invert.
4.7.2.3 M ATCH /I NVERT
The AL-2 relay (formerly Alarm-2 relay) is set up to reflect the
currently selected background gas. The relay is installed at the factory
such that the relay is energized when O
2
is selected as the background
gas. It is de-energized when N
2
is selected.
The relay output is available from the 50-pin equipment connector at
pins 42, 43 and 44 according to Table 3-4. The logic of the relay can be
changed using the Match/Invert function in the BACKGROUND GAS
menu.
Table 4-2 describes the AL-2 relay status for the selected
background gas under MATCH and INVERT options.