H74.0.14.6C-05
Operating Manual GMH 3692
page 8 of 12
6
Oxygen Measuring in Gases- Please Note
The GMH 369x is designed for measuring the oxygen partial pressure or the oxygen concentration (%vol,
calculated from partial pressure and ambient pressure) in gases. Please keep in mind:
The sensor hast o calibrated regularily, e.g. at fresh ambient air
The calibration and the measuring are pressure depending!
The instrument automatically measures the ambient pressure, be sure, that instruments pressure is
the same like the pressure at the sensors membrane. For the full automatic compensation a precision
pressure sensor is integrated in the instrument.
The sensor temperature has to be the same like the gas temperture!
Temperature differences may falsify the results!
Please have in mind that temperature adoption of the sensor and the air may take several hours.
A suitable ventilation or gasflow around the sensor would speed up this process significantly.
The sensor consists of a sensing element (GOEL xxx) enclose in a sensor housing (GGO/ GGA/GOO).
When purchasing a Sensor GGO/GGA/GOO xxx, a sensor element is already integrated, e.g. a GGO 370:
contains housing GGO and a sensor element GOEL 370.
6.1 Choice of Sensing Elements#
GOEL 370:
Universal sensor element with special protection measures especially for diving application (“Nitrox”).
Very long life time, also suitable for application with larger CO
2
concentrations.
GOEL 380:
Fast responding for
low oxygen concentration
e.g. protection atmosphere below 1%, max 25%.
For application without larger CO
2
concentration.
Sensors are not allowed to used in „under-Water-Diving-Application (e.g. Rebreather)
DANGER
6.2 Application of the different sensor types GGO ..., GOO ... and GGA
GGO (closed sensor)
For measurements at atmosphere
and in systems without over or under pressure the GGO... is sufficient.
Additionally the GGO can be screwed tightly into systems with small over or under pressure.
Attention! Mind the maximum pressure and the maximum pressure difference at the membrane.
If instrument and sensor pressure are different, it will be compensated wrong!
GOO 370 / 380 (open sensor)
The sensor is equipped with drillings at the end and because of its special construction the measuring gas
streams optimally around the sensor. No pressure can appear while gas blows to the sensor, which
otherwise would result in erroneous measures. The temperature compensation speed of the sensor also is
optimised by this design.
Especially the measuring of gases from compressed gas bottles
, where the expansion of the gas
leaving the bottle lowers the temperature, is optimised with regard to the temperature compensation and
pressure errors. The gas flow should be chosen in a suitable range, where no overpressure can happen,
esp. if the sensor is connected directly to the source e.g. by means of a tube.
GGA (closed sensor with pressure port)
Not suitable for GMH 3692
