Advanced Instruments, Inc.
The display will not shift automatically. Instead, when the oxygen reading (actually the sensor’s signal
output) exceeds 110% of the upper limit of the current range an OVER RANGE warning will be displayed.
Once the OVER RANGE warning appears the user must advance the transmitter to the next higher range
via the menu and keypad Press MENU, select MANUAL SAMPLING, press ENTER, select the appropriate
MANUAL RANGE and press ENTER again.
Start-Up is Complete…Proceed to Calibration
Zero Calibration
In theory, the oxygen sensor produces no signal output when exposed to an oxygen free sample gas.
However, the transmitter will generate an oxygen reading when sampling oxygen free sample gas due to:
Contamination or quality of the zero gas
Minor leakage in the sample line connections
Residual oxygen dissolved in the sensor’s electrolyte
Tolerances of the electronic components
Recommendation
Zero calibration is recommended for measurements below 0.1% on the 0-1% range only. At ranges
above 0-1%, the overall zero offset is negligible and does not contribute any error in measurements.
Procedure
•
Zero calibration should precede the span calibration and once performed should not have to be
repeated with subsequent span calibrations. Normally, zero calibrations are performed when a
new sensor is installed or changes are made in the sample system connections.
•
The overall zero offset from oxygen dissolved in the sensor electrolyte and or from the
electronics is typically less than 0.05% (on 0-1% range). This offset can be nulled by using the
zero calibration. Since the magnitude of zero offset is low, it is not necessary to perform zero if
the measurements are to be made on ranges above 0-1% range.
Caution: Prematurely zeroing the transmitter can cause a negative reading in both the
ZERO
•
Access the MAIN MENU by pressing the MENU key.
•
Advance the reverse shade cursor using the ARROW keys to highlight CALIBRATE.
•
Press the ENTER key to select the highlighted menu option.
12.5%
OVER RANGE
Manual Range
0-10%
77 F
100 KPa
22
