BRUEL & KJAER 2206 - 3 Operation; General Considerations; Batiery Considerations; Mounting of Microphone

3. OPERATION
3.1. GENERAL CONSIDERATIONS
When connecting or disconnecting to microphone be certain that the power is switched
off. In dry weather static electricity should be discharged from one's body before one fits
or removes the microphone. Only light finger torque should be applied when connecting
the microphone and extension rod together. Dust and foreign bodies should be kept off
the diaphragm, which must not be touched with any object. If the diaphragm must be
cleaned then the task should be done extremely carefully using cotton wool . Dry and
preferably warm conditions are recommended for storing the instrument.
3.2. BATTERY CONSIDERATIONS
The 2206 is powered by a single 1 ,5 V battery ("C" Cell, or Type RT4 in IEC publica-
tions). To insert the battery, unscrew the battery housing cover using a coin then place
the battery inside with the central (+) contact pointing outwards. Replace the housing
cover, but do not screw it back too tightly.
A good quality dry cell gives ten hours of continuous operation. The battery should be
removed, if the instrument is not going to be used for a long time, to prevent possible
battery leakage.
3.3. MOUNTING OF MICROPHONE
The condenser microphone normally supplied with the 2206 is the 4148. This micro-
phone has a nominal capacitance of 1 7pF.
A
high impedance Input Adaptor (UA 0208) is necessary to match the small capacitance
of the microphone to the rest of the circuitry. The UA 0208 contains a high impedance
(2000 M 0 in parallel with 50pF) field effect transistor (FET) input circuit. A special
cable,
AO 0063, is available for insertion between the meter and adaptor UA 0208 so
that the microphone can be used well away from the meter if required.
Cables cannot be used between the microphone cartridge and the adaptor because of
the large capacitance of a cable compared to that of the microphone. A flexible swan
neck extesion (UA 0196) can be used, however, after first removing the insulating
washer on the 4148, which is there to prevent the microphone from being inadvertently
connected to the wrong polarisation voltage via one of 8 & K preamplifers designed to
supply 200 volts polarisation. ·
In all
applications where there is a risk of water condensing inside the microphone a De-
humidifier UA 0308 should be inserted between the microphone and the Input Adaptor
UA 0208.
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