5
Weatherproof Microphone Unit Type 4184 (Type 3639-G)
Fig. 3
Weatherproof
Microphone
Type 4184 with
adaptor, fitted on the
top of a water pipe
The weatherproof microphone is the ultimate outdoor microphone for permanent
installation in all environmental conditions, while ensuring that the NMT complies with
IEC 61672 Class 1 requirements.
It ensures accurate noise measurements in most humid and corrosive atmospheres with
rain protection according to IEC 529 IP44, and operation all the way up to 100% RH.
The microphone has excellent omnidirectional characteristics, allowing high accuracy with
fixed orientation and less dependency on the operator’s expertise. The CIC function is
complemented by a built-in test sound source (at 1 kHz) for actual calibration. For more
information see Product Data
.
Environmental Protection
Fig. 4
Noise Monitoring
Terminal Type 3639-E/
G – the electronics
inside the NMT are
well protected
The NMT has been specifically designed to operate unattended in inhospitable
environments, protecting the contents from weather and unwanted
interruptions due to tampering, vandalism, theft, etc.
All equipment is protected inside two interlocking cabinets. This dual cabinet
construction ensures optimal protection of the equipment, while securing a
growth path for future NMT solutions from Brüel & Kjær. A low-temperature
protection kit is available for continuous operation of the NMT under extreme
weather conditions
*
when running with mains power supply. The NMT also
includes a watchdog function that ensures that, in the rare event of the NMT
not operating (such as loss of power), it automatically restarts and continues
measuring.
The robust, durable, weatherproof cabinet includes a kit for fastening the
cabinet to a wall, a box-sectioned or tubular mast, a lamp post or similar
(diameter 40 – 200 mm, more if required) and the door seals the cabinet from
the outside environment and helps prevent tampering. The cabinet is well-
protected by a weatherproof locking mechanism on the door, and a padlock
can be mounted for security. The NMT also sends a signal to the remote
software when the door is open, allowing unauthorised intrusion to be detected and recorded. In
addition, protection is provided for cabling to reduce the risk of tampering or accidental damage.
The system includes one or two batteries for independent operation, and as a backup in the event of
power loss. It is possible to change the battery during operation for ease of maintenance and increased
independence. The batteries are charged whenever external AC or DC is applied to the NMT and charging
the batteries completely will take up to 24 hours.
Brüel & Kjær can supply External Charger ZG-0453 for charging the batteries, once they have been
removed from the NMT. The batteries can be fully charged in ten hours and one charger is needed per
battery.
* Contact your local Brüel & Kjær representative for more information.
