Analytical-industries GPR-3100 Series Oxygen Purity Analyzer Manuel d'utilisateur télécharger pdf (Page 26)

Advanced Instruments Inc.

5 Operation

GPR-3100 Rev 2/05 19

Calibration - General Guideline

Zeroing the analyzer is recommended for oxygen measurements requiring accuracy greater than +/-

0.5% oxygen and when the analysis is carried out on 0-100% range. The ZERO OFFSET is not required if

the analysis is carried out on the suppressed ranges.

Caution: Do not attempt to calibrate the unit in the atmosphere air (20.9% oxygen) and use the

analyzer for either elevated or high purity oxygen measurements.

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.

Certifying Medical Grade Oxygen:

The FDA requires the use of certified gases for zeroing and calibrating analyzers used in certifying

medical grade oxygen.

The analyzer zero gas must be a certified cylinder of nitrogen with a minimum purity of 99.9%.

Once the analyzer has been zeroed (as described below), calibrate (as described below) with a

certified cylinder of oxygen with a minimum purity of 99.2%.

Advanced Instruments Inc. recommends zeroing and calibrating the analyzer at least every 8 hours or

before each certification.

Non-medical grade oxygen applications:

In non-medical applications the analyzer does not require zeroing before every calibration. It is

recommended the analyzer be calibrated at least monthly. In most cases a nitrogen zero gas of 99%

minimum purity and a span gas of 95-100% oxygen purity is sufficient.

Zero Calibration

In theory, the oxygen sensor produces no signal output when exposed to an oxygen free sample gas.

However, the analyzer will generate an oxygen reading when sampling oxygen free sample gas due to:

¾ Contamination or quality of the zero gas

¾ Minor leakage in the sample line connections

¾ Residual oxygen dissolved in the sensor’s electrolyte

¾ Tolerances of the electronic components

Zero calibration is recommended for very low percentage measurements on the 1% range only. It is not

practical on higher ranges, such as ambient monitoring, because of the low value, normally < 0.1%, is

not material to the accuracy of higher level measurements.

Procedure:

In the event the user desires to conduct a zero calibration, with a few differences a zero calibration

follows the same procedure as the span calibration described above. Differences include substituting a

suitable zero gas for the span gas and allowing the analyzer 24 hours with flowing zero gas to determine

the true zero offset (a stable reading evidenced by a horizontal trend on an external recording device) of

the system before conducting the zero calibration. A minimum of 24 hours is required for the sensor to

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Analytical-industries GPR-3100 Series Oxygen Purity Analyzer Manuel d'utilisateur Page 26