© 2014 All rights reserved. Data subject to change without notice.
47
Rev. E | 2014.10
GEM-II - Operation Manual
8 CalIbRaTIon
8.1 Calibration specifications
8.1.1 Gas
Calibration span gases should be at least ± 5% accuracy and have a current date stamp. Gas
generators should have a current dated cell installed. Service personnel should flow zero
emissions air or 20.9% volume Oxygen (O
2
) before attempting to null adjust toxic gas sensors. In
some cases Nitrogen (N
2
) can be substituted for zero air. Contact CETCI for clarification. Nitrogen
(N
2
) is required to null (zero) Oxygen (O
2
) and Carbon Dioxide (CO
2
) sensors.
If an inappropriate concentration of span gas is applied during calibration, calibration may
succeed but it does not mean the equipment has been calibrated properly. CETCI is not
responsible for improperly calibrated transmitters. Follow manual instructions carefully.
8.1.2 Exception
Flow Nitrogen (N
2
) over Oxygen (O
2
) sensors before attempting to null adjust them. If the service
person is confident of air quality and is careful (do not exhale in the direction of the Oxygen
sensor being serviced while span adjusting). Oxygen in the breathing environment can be used
as a fairly accurate source of span gas (20.9% volume) “in a pinch”. It is not recommended to use
this procedure for all span adjustments of Oxygen sensors.
8.1.3 Regulators & Flow
Calibration gases that are lighter than or the same weight as air (CO, O
2
, etc.) should be flowed at
0.5 LPM. Gases heavier than air (NO
2
, Cl
2
, etc.) should be flowed between 0.5 and 1.0 LPM. Fixed
flow regulators provide more accuracy. Gases should be flowed over the sensor for at least 2.5 - 4
minutes. Carbon Monoxide sensors settle out very quickly, but sensors for reactive gases (NH3,
etc.) will take longer to stabilize to the calibration gas. All cylinder regulators supplied by CETCI
use a fixed flow orifice.
8.1.4 Adapters
The proper calibration adapter should be utilized to allow the gas to properly diffuse around the
sensor. They are available from CETCI. A humidification chamber is recommended to be utilized
for all catalytic and solid state sensors except Ammonia. This is also available from CETCI.
Содержание GEM-II
Страница 1: ...Operation Manual www critical environment com GEM IISelf Contained Gas Detector Rev E 2014 10...
Страница 58: ...58 2014 All rights reserved Data subject to change without notice GEM II Operation Manual Rev E 2014 10 NOTES...
Страница 59: ...2014 All rights reserved Data subject to change without notice 59 Rev E 2014 10 GEM II Operation Manual NOTES...
