Servomex xendos 1800 Series, Quick Start Manual

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xendos 1800 Series
12
4 CALIBRATION
4.1 Zero and Span adjustment
CAUTION
The pressure and flow rates of the zero and span gases used to
calibrate the xendos analysers must not exceed the values detailed in
the table in
Section 2.5 Sample Gas Connection .
The analyser should have been running for at least four hours before carrying
out calibration. It is recommended that the sample outlet from the xendos
analyser be vented directly to atmosphere.
In oxygen purity applications changes in atmospheric pressure can affect the
measurement. Fitting the Back Pressure Regulator option will reduce this effect.
(See the table in Section 7.1)
The zero and span calibration gas can be introduced into the analyser via a 3-
way valve fitted into the sample inlet pipework or directly into the analyser
sample inlet by disconnecting the sample pipework and isolating the sample
flow elsewhere.
1. Open the hinged front left cover using a 5mm allen key.
2. To set the zero, introduce zero calibration gas, this should be high purity
nitrogen (99.9% min.). Once the reading has stabilised, adjust the zero
control so that the display reads 0.0% oxygen.*
3. To set the span, introduce span calibration gas, normally this can be good
quality clean dry instrument air (nominally 20.95% oxygen) is recommended
for all ranges except where the sample will have an oxygen content greater
than 21%. For samples with oxygen content above 21%, a suitable certified
calibration gas is essential. Once the reading has stabilised, adjust the span
control so that the display reads 20.9 % oxygen* or the actual level of
oxygen in the calibration gas cylinder.
* with the optional 4.5 digit display board, the zero can be set to 0.00% and
span to 20.95%
The calibration should be checked either weekly, monthly or 3 monthly
depending on application.