Norsonic Nor1212, Instruction Manual

6 

Technical description 

further protection, the ports are covered with a water-repellent mesh. This 
also prevents the microphone from dust and insects. 

The tube is made of polyacetal (POM). The material is durable and has a 
low thermal conductivity compared to metal. This low thermal 
conductivity will have the effect of raising the temperature of the 
microphone and preamplifier above the ambient temperature. This heat 
gain is caused by the power consumption of the preamplifier. Even a 
small temperature rise will prevent condensation of water within the 
microphone during humid weather conditions. 

For applications in extremely humid conductions, the preamplifier Nor 
1201 or Nor1206 may be further heated by applying power to the internal 
heating element. See the handbook for Nor1201 for further details. 
Alternatively, a desiccator type TA202 may be placed between the 
microphone and the preamplifier. The desiccator absorbs water and hence 
provides dry air to the microphones back vent. The desiccator needs to be 
regenerated from time to time; see section 5 for information about this 
maintenance operation. 

Placing the microphone inside a long rod results in the acoustic 
directional response being almost symmetrical above and below the 
horizontal plane through the acoustic ports. This makes the microphone 
system applicable for monitoring of aircraft overhead as well as industry- 
and traffic-sources on the ground. 

Access to the microphone is achieved by removing the upper part which 
is simply unscrewed from the main body. 

The base of the main body is sealed by means of the base screw. This 
base screw also contains a threaded hole for mounting the microphone 
system on a mast.

Figure 2.2 Microphone system 
Nor1212