1、BRITISH STANDARD BS 6809:1987 Method for Calibration of radiometers for use in fire testing UDC 535.214.4.089.6:536.468.001.4BS6809:1987 This British Standard, having been prepared under the directionof the Fire StandardsCommittee, waspublished under the authorityof the Board ofBSIand comes into eff
2、ect on 27February1987 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference FSM/1 Draft for comment84/40208DC ISBN 0 580 15699 0 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Fire Standards C
3、ommittee (FSM/-) to Technical Committee FSM/1, upon which the following bodies were represented: Association of British Roofing Felt Engineering Equipment and Materials Users Manufacturers Association Association of Building Component Eurisol (UK) Association of Manufacturers of Manufacturers Ltd. M
4、ineral Insulation Fibres Association of Structural Fire Protection Fibre Building Board Organization (FIDOR) Contractors and Manufacturers Fibre Cement Manufacturers Association British Coal Limited British Fire Services Association Fire Insurers Research and Testing British Floor Covering Manufactu
5、rers Organisation (FIRTO) Association Fire Offices Committee British Plastics Federation Fire Protection Association British Railways Board Flat Glass Manufacturers Association British Rigid Urethane Foam Manufacturers Flat Roofing Contractors Advisory Board Association Gypsum Products Development A
6、ssociation British Wood Preserving Association Home Office Cement and Concrete Association Institution of Fire Engineers Chemical Industries Association Mastic Asphalt Council and Employers Chief and Assistant Chief Fire Officers Federation Association National Council of Building Materials Concrete
7、 Society Producers Constructional Steel Research and National Grp Construction Federation Development Organisation Rapra Technology Ltd. Department of Education and Science Royal Institute of British Architects Department of the Environment for Northern Timber Research and Development Association Ir
8、eland United Kingdom Antimony Oxide Department of the Environment (Housing and Manufacturers Association Construction Industries) United Kingdom Atomic Energy Authority Department of the Environment (Property Warrington Fire Research Centre Services Agency) Wood Wool Slab Manufacturers Association D
9、epartment of Transport (Marine Directorate) Yarsley Technical Centre Ltd. Electricity Supply Industry in England and Wales The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Department of the Environment Building Greater London Council Resea
10、rch Establishment (Fire Research Station) Amendments issued since publication Amd. No. Date of issue CommentsBS6809:1987 BSI 10-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Principle 1 4 Apparatus 1 5 Test environment 2 6 Setting up procedure
11、 2 7 Calibration 2 8 Calculation of results 3 9 Report 3 Appendix A Accuracy of calibration 4 Appendix B Care of radiometers 4 Appendix C Guidance notes 5 Appendix D Suitable apparatus 6 Appendix E Procedure recommended for maintenance of a secondary standard of irradiance at a test laboratory 11 Fi
12、gure 1 Plan of track arrangement for calibration of radiometers showing extent of parallel and perpendicular travel 8 Figure 2 Isometric view showing arrangement of radiometer mounting assembly 9 Figure 3 Detail of positioning device for radiometers 10 Figure 4 Side elevation of apparatus showing me
13、thod of positioning radiometers 11 Publication referred to Inside back coverBS6809:1987 ii BSI 10-1999 Foreword This British Standard has been prepared under the direction of the Fire Standards Committee and describes a method for the calibration of radiometers used in fire testing. It should be of
14、value to those working in industry and research who are concerned with the measurement of heat transfer by thermal radiation. A number of fire tests described in British Standards and International Standards published by the International Organization for Standardization (ISO) require test specimens
15、 to be exposed to specified levels of irradiance. It is therefore necessary for fire test laboratories to be able to maintain working-standard radiometers to measure irradiance. This standard describes a method for the calibration of radiometers for use as working standards by comparison with a radi
16、ometer of known sensitivity referred to as a secondary standard. The latter will have been calibrated by reference to a defined primary standard of irradiance. Since the standard is intended to apply to radiometers for use in fire tests, the radiator employed is limited to a surface temperature in t
17、he range of800 C to1000 C. NOTEA suitable primary standard of irradiance is maintained by the Fire Research Station, Boreham Wood, Herts WD62BL. The calibration of radiometers for use as primary and secondary standards requires considerable expertise and equipment outside that normally available in
18、a fire testing laboratory and is not covered by this standard. For information on the calibration of primary standards and for a detailed account of the principles of the measurement of thermal radiation reference should also be made to J. Sci. Inst., 40, pp216220, May1963, Simms, D.L. seeC.6), and
19、that they do not become entangled in any mechanism when it is moved. If a water-cooled or forced air-cooled radiometer is to be tested, then connect the appropriate supply and ensure that the flow rate is in accordance with the manufacturers recommendations. 6.2.2 Adjust the radiometers in turn hori
20、zontally, vertically and in angular orientation so that when brought into the test position their receivers lie in the same plane parallel to the plane of the radiant panel, with the centres of the receivers on the normal from the centre of the panel. Ensure that the receivers of the radiometers are
21、 clean and not obstructed in a sight line to the radiator when in the test position. Place small screens in front of the radiometers to shield them from the radiator. NOTEAs far as possible, the radiometers should be screened from radiation except during actual readings. 6.2.3 Connect the secondary-
22、standard and working-standard radiometers independently to the recording instrumentation using appropriate leads. Turn on the radiator and adjust its control to give an operating temperature in the range800 C to1000 C. Allow the radiator to reach a steady state before commencing measurements. NOTELa
23、boratories supplying instruments for calibration should be aware that with a new working-standard radiometer or one which has not been previously used, it is advisable to age the receiver artificially before a calibration is carried out to avoid, or reduce, initial drift in sensitivity. It is recomm
24、ended that this be done by exposing the receiver to radiation for20h to25h in a series of exposures of several hours duration, at an irradiance approximating to the maximum at which it is likely to be used. With some types of radiometer it may be advisable to monitor sensitivity and continue ageing
25、until it has stabilized. 7 Calibration 7.1 Switch on the recording instrumentation, allowing any necessary time for warming up.BS6809:1987 BSI 10-1999 3 7.2 Remove any screens shielding radiometers from the radiator. 7.3 Set the secondary-standard radiometer at its central position on the mounting a
26、pparatus and lock it in this position. 7.4 Move the radiometer towards the radiator to a suitable position and lock it in this position. 7.5 Continue the exposure in this position until the value recorded from the radiometer is essentially constant over a period of1min. Note the radiometer output (S
27、 1 ). 7.6 Move the working-standard radiometer to the position occupied by the secondary-standard radiometer. 7.7 Continue the exposure in this position until the value recorded from this radiometer is essentially constant over a period of1min. Note the radiometer output (W). 7.8 Return the secondar
28、y-standard radiometer to its central position and repeat7.5, obtaining an output (S 2 ). 7.9 Repeat the measurements, alternating the working-standard and secondary-standard radiometers until two successive measurements from the latter differ by less than1% (seeC.6). 7.10 Repeat7.2 to7.9 with the mo
29、unting apparatus at decreasing distances from the radiator until at least five different levels of irradiance have been used (seeAppendix A). Ensure that the actual distances used result in irradiance levels that cover the required calibration range of the working-standard radiometer and are evenly
30、spread over that range. From the final position, repeat7.2 to7.9 with the mounting apparatus at increasing distances from the radiator until at least five different levels of irradiance have been used making a total of at least10. 8 Calculation of results 8.1 General Derive the irradiance correspond
31、ing to an output of W from the working-standard radiometer from the arithmetic means of those two consecutive values of S bracketing this reading (see7.9) and the calibration data available for the secondary-standard radiometer. Present the results either graphically (see8.2) or mathematically (see8
32、.3). 8.2 Graphical presentation 8.2.1 Tabulate the irradiance and the output of the working-standard radiometer at each distance from the radiant panel used. 8.2.2 Construct a graph of irradiance as ordinate against output voltage from the working-standard radiometer as abscissa. 8.2.3 The graph now
33、 represents the calibration of the working-standard radiometer with reference to the secondary-standard radiometer used. 8.3 Mathematical presentation 8.3.1 Express the calibration in the form of a regression equation of irradiance on millivolt output, using the usual statistical techniques. For man
34、y instruments a linear regression equation will be suitable but some instruments require second-order regression techniques to express adequately the relationship between output and irradiance. 8.3.2 Before subjecting the data to statistical or other analysis, examine them for outlying observations;
35、 readings occasionally arise which appear to be substantially out of line with the main body of the readings, and which could affect substantially an overall calibration obtained, for example, by regression techniques. If such readings are noticed at the time of the laboratory work repeat them and d
36、iscard them if they are not confirmed. Discard outlying readings where a physical explanation exists for questioning their validity, for example where some disturbance is known to have occurred. NOTEWhere no physical reason exists for suspecting the accuracy of an outlier then an objective statistic
37、al test may be required to decide whether to retain or to exclude it. 9 Report The report shall include the following. a) Reference to this British Standard. b) Reference to the source of calibration of the secondary-standard radiometer and the date of its last calibration. c) Identification of the calibrated working-standard radiometer (e.g.manufacturer, model, serial number). d) Irradiance range employed. e) Date of calibration. f) Results as detailed in clause8. g) Name of calibrating laboratory. h) Name of sponsor.
