Analytical Industries GPR-3500 MO Portable Oxygen Analyzer - Manual (Page 19)

Advanced Instruments Inc.
19
Span Calibration
Maximum drift from calibration temperature is approximately 0.11% of reading per °C. The analyzer has been calibrated at the factory.
However, in order to obtain reliable data, the analyzer must be calibrated at the initial start-up and periodically thereafter. The
maximum calibration interval recommended is approximately 3 months, or as determined by the user’s application.
Calibration involves adjusting the portable oxygen purity analyzer electronics to the sensor’s signal output at a given oxygen standard.
As mandated by the FDA, calibration requires the use of certified zero (99.9% nitrogen minimum purity) and span (99.2% oxygen
minimum purity). For optimum accuracy and to take advantage of the portable oxygen purity analyzers’ inherent accuracy of 0.1%,
perform the zero and span calibration before each certification. Otherwise calibrate every eight (8) hours.
Recommendation: Initiate the DEFAULT SPAN procedure before performing either a ZERO or SPAN CALIBRATION.
Caution: The user must ascertain that the oxygen reading (actually the sensor’s signal output) has reached a stable value within the
limits entered below before entering the span adjustment. Failure to do so will result in an error.
Caution: Do not attempt to span the portable oxygen purity analyzer with air or 21% oxygen and then operate it for either elevated
or high purity oxygen measurements.
Medical grade oxygen:
The FDA requires the use of certified gases for zeroing and calibrating analyzers used in certifying medical grade oxygen. Advanced
Instruments Inc. recommends zeroing and calibrating the analyzer before each certification.
The analyzer zero gas must be a certified cylinder of nitrogen with a minimum purity of 99.9%. Once the analyzer has been zeroed
(described below), calibrate (described below) with a certified cylinder of oxygen with a minimum purity of 99.2%.
Non-medical grade oxygen applications:
In non-medical grade oxygen applications the analyzer does not require zeroing before every calibration. It is recommended the
analyzer be calibrated at least monthly. In most cases nitrogen zero gas of 99% minimum purity and a span gas of 95-100% oxygen
purity is sufficient.
Default Span
The software will set the SPAN adjustment based on the average oxygen reading (actually the sensor’s signal output) at a specified
oxygen concentration. For example, when a span gas is introduced, the micro-processor will display an oxygen reading within +50% of
the span gas value. This feature allows the user to test the sensor’s signal output without removing it from the sensor housing.
1. Access the MAIN MENU by pressing the MENU key.
2. Advance the reverse shade cursor using the ARROW keys to highlight CALIBRATE.
3. Press the ENTER key to select the highlighted menu option.
4. The following displays appears:
MAIN MENU
AUTO SAMPLE
MANUAL SAMPLE
CALIBRATE
24.5 C 100 KPA
>>>
CALIBRATION
SPAN CALIBRATE
ZERO CALIBRATE
DEFAULT SPAN
DEFAULT ZERO
OUTPUT SPAN
OUTPUT ZERO
Required components: Refer to Installing Span Gas section above.
Procedure – Span Calibration:
This procedure assumes a span gas under positive pressure and is recommended for a portable oxygen purity analyzer without an
optional sampling pump, which if installed downstream of the sensor should be placed in the OFF position and disconnected so the
vent is not restricted during calibration.