Bosch Appliances LBC 325X LBC 3262/00 Ambient SPL Temperature sensor, Description, Wiring

Intellivox DDC Installation Manual Appendix EN 20

Notes for type RS-232 to RS-485 adapter:

•Both ends of the RS-232 to RS-485 connector have the same 9p female sub-d connector. Be careful to install it in the proper way.

•The +9 V (pin 9) at the RS-232 side of the adapter should be connected to an external + 9 V / 50 mA DC power supply in case the power delivered by the PC (RTS or DTR) is insufficient. This might be the case with large cable lengths.

•RTS and CTS are internally connected, DTR and DSR are also internally connected.

3.4 LBC 3262/00 Ambient SPL and

temperature sensor.

Description.

The Intellivox electronics module is equipped with an external terminal (labeled ambient noise / temp) to connect a sensor for the ambient SPL and temperature measurement. Although the unit is able to operate normally without the sensor, it is needed when the auto gain function or the frost protection is used.

The temperature is measured by a NTC resistor. By means of a software correction table the non-linear resistance characteristics of the NTC are compensated and converted into a degree scale. The SPL is measured by an electret microphone, rectified and converted to a dB scale. The microphone is powered by the amplifier module through the connector.

Location of the sensor.

Both NTC and microphone are mounted in a single compact enclosure which can be located at a certain distance from the column. In most situations the best location is determined by the microphone (see also chapter 2.2). The auto gain will only work correctly if the diffuse ambient noise level is used as a reference. This means that the microphone should be kept away from direct sound sources such as talking people, outlets of the air conditioning system or other loudspeakers.

The implemented software protocol freezes the volume setting when an audio signal is present in order to prevent ‘hunting’ of the column’s gain setting caused by its own radiated acoustical energy.

•Although the circuit of the combined sensor is not complex, the specific characteristics are very important for a correct interpretation of the measured values. For this reason it is strongly advised to use the appropriate factory tested sensor (see chapter 3.1 for order codes).

Wiring.

For reasons of RFI immunity and optimum noise characteristics two different ground terminals are implemented. The terminal labeled GND is connected directly to the chassis, while the terminals labeled AGND are reference ground terminals.

•GND and AGND should be kept apart under all circumstances!

For correct wiring an asymmetrical shielded 2 way cable with overall shield is advised. Alternatively the twin twisted cable, which is also optionally in use for the RS-485 network interface, can be used. Reference source not found. (next page) show the correct wiring diagram for both cables.

Fig 16 Wiring configuration using asymmetrical cable type

Bosch Security Systems July 2003