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Operating Instructions Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 94
6.8.5. Auto Range Mode (AUTO)
In AUTO range mode, the analyzer automatically switches the reporting range between two user-defined
ranges (low and high). The unit will switch from low range to high range when the CO
2
concentration
exceeds 98% of the low range span. The unit will return from high range back to low range once both the
CO
2
concentration falls below 75% of the low range span.
In AUTO Range mode the instrument reports the same data in the same range on both the A1 and A2
outputs and automatically switches both outputs between ranges as described above. Also, the RANGE
test function displayed on the front panel will automatically switch to show which range is in effect.
The high/low range status is also reported through the external, digital status outputs (Section 6.15.1.1).
To set individual ranges press the following keystroke sequence.
SAMPLE* RANGE = 500.000 PPM CO2 =X.XXX
< TST TST > CAL SETUP
SETUP X.X
PRIMARY SETUP MENU
CFG DAS RNG
E
PASS CLK MORE EXIT
SETUP X.X RANGE CONTROL MENU
MODE
SET UNIT EXIT
SETUP X.X RANGE MODE: SNGL
SNGL DUAL AUTO ENTR EXIT
EXIT x 2 returns
to the main
SAMPLE display
SETUP X.X RANGE MODE:
A
UT
O
SNGL DUAL AUTO ENTR EXIT
SETUP X.X RANGE CONTROL MENU
MODE
SET UNIT EXIT
SETUP X.X HIGH RANGE: 500.0 Con
c
0 0 5 0 0 .0 ENTR EXIT
SETUP X.X LOW RANGE: 500.0 Con
c
0 0 5 0 0 .0 ENTR EXIT
Toggle the numeral
buttons to set the
LOW and HIGH
range value.
ENTR accepts the
new setting, EXIT
ignores the new
se tting.
CAUTION
In AUTO range mode the LOW and HIGH ranges have separate slopes and offsets
for computing CO2 concentration.
The two ranges must be independently calibrated.
NOTE
Avoid accidentally setting the low range of the instrument with a higher span limit
than the high range. This will cause the unit to stay in the low reporting range
perpetually and defeat the function of the AUTO range mode.