Instruction Manual MIC type EC-912
Revision no.4
5 / 38
General information
WARNING
THE MEASURING IONIZATION CHAMBER EC-912-10
CONTAINS A WEAK RADIOACTIVE SOURCE. DO NOT
ATTEMPT TO DISMOUNT THE MIC WITHOUT FOLLOWING
THE SAFETY PRECAUTIONS GIVEN IN SECTION 5.1.1 .
Introduction
Smoke density can be measured using several different techniques. However, for reference
measurements of smoke density in connection with testing of ionization smoke detectors for automatic
fire detection systems, it is advantageous to use a measuring instrument based on the ionization
chamber principle. This is because of the complex nature of smoke, which means that measuring
errors are likely to occur if the reference measuring instrument reacts to other properties of the smoke
than the detector under test.
Different reference ionization chambers have been developed in the past. See ref. [1][3][4]. However,
since the measuring characteristics of the ionization chamber depend on several parameters,
including the design of the ionization chamber, it is important to reach international acceptance of one
particular ionization chamber design in order that measuring results may be comparable in general.
The measuring ionization chamber (MIC) which is the smoke sensor in smoke measuring equipment
EC-912 has reached this status. The chamber, which is originally designed by Cerberus AG,
Switzerland [2][3], has been included in the European standards for smoke alarms EN14604 [5] and
smoke detectors EN54-7 [6] issued by CEN
1
and the UL
2
standards UL 217 and UL 268 [8][9].
Furthermore, the chamber is also specified in “ISO
3
7240-
7 Fire detection and alarm systems” for point
smoke detectors.
The MIC instrument can be used alone or in combination with different types of optical smoke
measuring equipment.
1
CEN:
European Committee for Standardization
2
UL:
Underwriters Laboratories Inc.
3
ISO:
International Organization for Standardization