Vaisala GMP343 - Manual (Page 18)

User’s Guide ______________________________________________________________________
16 ___________________________________________________________________M210514EN-E
Optics Heating
Two heating elements are placed in the optics; one behind the mirror and
one behind the window of the sensor. Heating should always be turned on
when there is a risk of dew formation on the optics surface. The heating
maintains the surface temperature of the optics a few degrees above the
ambient temperature.
The heating is disabled by default. For instructions on how to control the
optics heating, refer to section
Setting the Optics Heating ON/OFF on page
60 .
Gas Sampling
There are two GMP343 models available: a flow-through model and a
diffusion model.
Diffusion Sampling
No sampling system is needed with the GMP343 diffusion model. The
diffusion filter and the plastic filter cover protect the measuring chamber
from dirt, water, and contaminants.
In order to have a quick measurement with very short response time the
filter can be removed; see section
Response time (90 %) on page 77 . In this
case the optics are openly exposed to contamination and cleaning of optics
may be necessary more often. For instructions on cleaning the optics, refer
to section
Changing the Filter and Cleaning the Optics (Diffusion Model
Only) on page 70 . Removal of the filter is not recommended if there is a
risk of getting water or dirt particles on the optics.
Flow-Through Sampling
The maximum gas flow rate is 10 liters/min. When using high flow rates,
please note how the flow rate affects the accuracy, see Specifications
Response time (90 %) on page 77 (flow dependence). The volume of the
internal measurement chamber is 59 ml ± 1 ml.
The gas sample must not include acidic gases.
NOTE The optics heating is automatically disabled when you connect the
GMP343 to a MI70 indicator.