9. Reference voltage # 4 ( about 2500 mV’s )
Options
Set the value of the reference voltage as read on a 3 3/4 digit multimeter (See Section 6.2 for further details).
2479.00 mV *
Set-up items 6 to 9 are used to calibrate the A/D of the instrument. This should be done 30 minutes or more after the
instrument has been on, approximately once every year. The calibration constants are retained in battery backed
memory unless a ‘COLD START’ is performed. Connect a 3 1/2 digit multimeter negative lead to the test point
marked ‘C’ to the right of the PCB on the inside of the door (labelled ‘REF VOLTS’). Measure the four voltages on
the test point marked 1 to 4 with the positive lead. Refer to Figure 6.2 in the 9070 manual. Enter the measured values
in set-up items 6 to 9. Whenever new values are entered the D/A section should be re-calibrated, Refer to Section 6.3.
10. AUTO OXYGEN SENSOR OFFSET
The sensor offset voltage is produced by small temperature differences within the oxygen sensor. The voltage is
normally between +3 to -3 mV. This error can be automatically removed by selecting ‘YES’.
The only time ‘NO’ should be selected is when the Analyzer is being used to measure gasses with between 16 and 26%
oxygen. The oxygen sensor offset should then be manually entered using set-up step 11.
Options
Yes *
No
11. SET O2 SENSOR OFFSET - MANUAL
The offset only needs to be set manually when the Analyzer is being used to measure gasses within 16 and 26% oxygen
content.
To check a sensor offset on site, the sensor must be sensing air and allowed to settle at the sensor operating temperature
for 30 minutes. Read the offset in ‘RUN’ mode in millivolts on the lower line. Enter the ‘SENSOR OFFSET’ value eg.
if offset value is -1.2 mV, enter -1.2 mV. The typical maximum is +/-3 mV.
If the manual entry method is being used, make sure that ‘NO’ to automatic entry is selected in set-up step 10 or the
manual value will be over written.
A new EMF offset must be entered whenever a new oxygen sensor is installed to calibrate for any offset an individual
sensor may have. This will have been set at the factory for a new or serviced instrument.
12. SELECT CO
2
CALIBRATION
Select either ‘ZERO’or ‘SPAN’ calibration of the CO
2
module by pressing the enter key in the usual way. Then return
to ‘RUN’ mode. The Analyzer will automatically enter the calibration mode. This will take up to 50 seconds. At the
end of the calibration, the mode selection in the menu will be returned to “CO
2
Cal Done ”. A 100% CO
2
gas bottle is
required for the ‘Cal Span’.
If ‘ZERO’ is selected, the CO
2
module will enter the automatic zero calibration mode. While the zero is being
calibrated, make sure that the sample gas is ambient air. If the sample is not stable during the 50 seconds zero
calibration period, the 9070 Analyzer will abort the calibration and instigate a “Co2 Gas Drift” alarm. If this occurs,
restart the zero calibration.
If ‘SPAN’ is selected, the CO
2
module will enter the automatic span calibration mode. While the span is being
calibrated, make sure that the sample gas is 100% CO
2
. If the sample is not stable during the 30 seconds span
calibration period, the 9070 Analyzer will abort the calibration and instigate a “Co2 Gas Drift” alarm. If this occurs,
restart the span calibration.
Options:
1. CO2 Cal Done *
2. Cal Zero
3. Cal Span
See also section 3.15, SENSOR CALIBRATION - CARBON DIOXIDE.
13. OUTPUT CHANNEL #1, 0-20mA or 4-20mA
Page 32 Teledyne Analytical Instruments 9070 Oxygen Analyzer
