Instruction Manual MIC type EC-912
Revision no.4
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General description
The smoke measuring equipment EC-912 comprises a measuring ionization chamber, a control
cabinet and a vacuum pump as shown in Fig. A.1.1 in Annex 1
.
The 19” control cabinet (CC) comprises either an Analog MIC Control Unit (AMCU) or an Intelligent
MIC Control Unit (IMCU) for the measuring ionization chamber, a flow control unit and a power supply.
The measuring ionization chamber (MIC) is placed in the location where the smoke density is to be
measured. The MIC is provided with a wind shield which makes the measurements of the device
independent of air movement in the location where it is mounted. This wind shield, however, makes it
difficult for the smoky air to merge into the measuring volume, so air is sucked through the MIC by a
vacuum pump (VP).
The air passes the flow control unit (FCU) on its way from the MIC to the VP. In the FCU the air can be
set to a flow rate with needle valve. An exchangeable filter is inserted before the flow meter in order to
reduce smoke deposits in this instrument.
The current in the MIC, which is proportional to the smoke density, can be measured with either an
Analog MIC control unit (AMCU) or an Intelligent MIC Control Unit (IMCU). The current in the MIC is
transformed into a proportional voltage in a built-in amplifier in the MIC. This voltage is fed to the MCU
and transformed to an expression for smoke density which can be presented on the display of the
AMCU. Furthermore, a recorder output is provided. The AMCU is provided with an electrical
calibration facility for check and setting of zero point and full scale deflection of the measuring system.
The IMCU gives you full control of the MIC via a standard Ethernet connection and can directly
replace the Analog MIC Control Unit placed in the 19” control rack without any modifications to the
existing hardware or cabling.
Applications
As mentioned in the introduction, the MIC smoke measuring equipment EC-912 is intended for
reference measurements of smoke density in type approval tests of smoke detectors. The following
two applications are typical in this area:
a)
Smoke tunnel (box) measurements.
The smoke measuring equipment is used to measure the actual smoke density in the
smoke tunnel where the detector under test is subjected to a slowly increasing smoke
density. The sensitivity of the detector is expressed in terms of the value of smoke
density measured at the moment of response. The detector sensitivity under specific
reference conditions and the change in sensitivity due to variations in the operating
parameters environment etc., are measured in this way.
b)
Measurements during fire sensitivity tests.
The smoke measuring equipment is used to measure the smoke density under the
ceiling in the fire test laboratory, where the detectors under test are subjected to
different test fire categories. The smoke readings are used for determining if the test
fires are correctly reproduced.