The apparatus uses an optical bench to allow the distance between the source and the detector to be adjusted while maintaining the relative alignment of the optical axes of the source and the detector. In order to allow for variations in response point the bench shall have an effective working length of at least 2,5 m.

　

The mounting stands used for the specimen and for other parts of the test equipment shall be constrained to move in a direction parallel to the axis of the bench. Means shall be provided to measure the distances between the individual bench-mounted items to an accuracy of ± 10 mm.

　

The detector mounting stand shall allow adjustment of the height and orientation of the detector such that its optical axis can be made coincident with the source optical axis. The detector mounting stand shall also allow the detector to be rotated about its optical axis and, independently, about a second axis perpendicular to the optical axis, and passing through the point of inter section of the optical axis and the plane of the detector sensing element(s). Means shall be provided to measure the angular rotations with an accuracy of ±5°.

　

An example of a suitable optical bench arrangement is shown in Figure A.1.

　

　

The radiation shall be produced by a gas burner, burning methane of not less than 98% purity, whose flame gives a stable (flicker-free) radiation output in the wavelength band in which the detector under test is intended to operate. The flicker in these bands shall be measured using an appropriate method. The root mean square (RMS) amplitude modulation of the radiation shall not exceed 5 %.

　

The effective radiation output shall be set by an aperture placed in front of the flame in such a position that the complete area of the aperture is filled by the flame when viewed from any allowable-position of the detector under test. For the purposes of this test method the aperture shall be considered as the source of radiation. The perpendicular axis through the center of the aperture shall be considered to be the optical axis of the source.

　

A gas burner suitable for use as a source is described in annex B.

　

　

A shutter shall be provided such that the specimen can be shielded from the radiation source. The shutter shall allow the duration of the exposure of the detector to the source to be controlled with an accuracy of ±2s.

　

　

The radiation from the source shall be modulated by suitable means (e.g. a rotating chopper disc) to provide the form of modulation specified by the manufacturer for the detector under test. The modulation frequency specified may be zero. If the manufacturer does not specify the modulation then measurements shall be carried out on a specimen chosen at random to determine the frequency corresponding to the peak of the detector's response. This frequency shall be noted and used for all subsequent measurements.

　

　

　

A radiometer shall be provided to monitor the irradiance produced by the source. The sensitive element of the radiometer shall be positioned at a point on the source optical axis at a distance in the range 1400 mm to 1600 mm from the aperture. The radiometer shall be fitted on a stand on the optical bench such that the distance from the aperture can be set within the specified range with a repeatability of ± 5 mm.

　

The wavelength response of the radiometer shall be appropriate to the detector under test and may be specified by the manufacturer. If the manufacturer does not specify a wavelength range then the radiometer shall respond to radiation only in the range 4,0μm to 4,8μm for IR detectors and 160 nm to 280 nm for UV detectors.

　

　

B.1 Figure B.1 shows an example of a burner (Maker burner) which is suitable for the source in A.2. The burner should be supplied with gas at a constant pressure to maintain constant radiated output.

　

　

　

　

　

　

　

A fire meeting the following parameters is intended to represent a fire burning with a yellow (sooty) flame:

　

a) Fuel:

　

Approximately 500 ml of n-heptane (pure) with approximately 3 % toluene (pure) by volume. The quantity of fuel used shall be sufficient to ensure that the complete base area of the tray is covered by fuel for the complete duration of the test(s). For safety, approximately 2 000 ml of water may be added to the tray before adding the fuel.

　

b) Arrangement:

　

The heptane/toluene mixture shall be burned in a square tray made from 2 mm thick sheet steel, with dimensions 330 mm x 330 mm x 50 mm deep.

　

c) Initial temperature:

　

The initial temperature of the fuel shall be (20 ± 10)℃.

　

d) Ignition:

　

Ignition shall be by any convenient means which does not affect the initial temperature or composition of the fuel.

　

e) End of test:

　

30 s after exposure of detectors to fire.

　

　

D.1 The test apparatus described in this annex and shown in Figure D.1 shall be manufactured so that it may be installed on the optical bench shown in Figure A.1 , without impeding the determination of response points. The light source shall consist of two identical 25 W tungsten incandescent lamps having clear glass envelopes and conforming to IEC 60064. The light source shall be supplied with 50 Hz AC.

　

The light source shall be mounted so that the direct line of sight from the detector sensor to the radiation source on the apparatus shown in Figure D.1 is maintained. The light source and the detector sensor shall be connected in such a way that the distance between the lamp stand and the detector is approximately 500 mm and is maintained at this fixed distance when the detector stand is moved.

　

The voltage supply shall be adjusted so that the colour temperature of the lamps is 2850 K ± 100 K. The distance between the lamps and the detector shall then be adjusted so that the lamps provide an illuminance in the plane of the detector sensor(s) of 100 lux.