testo 6621 - Product description 9
testo 6621-A02 (duct):
A = length of sensor protection cap used
Sensor protection cap Order code Length A in mm
Sintered stainless steel filter M 01 33
Wire mesh filter M 02 40.3
Sintered PTFE filter M 03 35
Metal protection cap (open) M 04 35
Plastic protection cap (open) M 05 25
Choice of filter dependent on exposure to particles:
Velocity Exposure to particles
none fine coarse
< 7 m/s M04/05 M02 M03
> 7 m/s M 01 M02* M01*
* also use condensation protection 0554 0166, serves as flow protection
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