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1038 CHAPTER 49 1951 Guide with a microscope, and the method yields important results when the nature or constituents of the dust are of interest. For a weight determination, a known volume of air is drawn through a porous crucible or thimble, and the weight gained by the thimble during the operation is the weight of the dust captured from the air sample.58 For precise work, the thimble must be dried in a desiccating chamber before weighing each time. The test method specified in the A.S.H.V.E. Code for Testing and Rating Air Cleaning Devices Used in General Ventilating Work is based on a weight method for evaluating the cleanliness of air after pass ing through an air cleaner.59 The Code has not filled all needs for an air cleaner testing method and the subject is now under investigation by the A.S.H.V.E. Research Laboratory. At the Nationcd Bureau of Standards a test method was developed for interested Government agencies, under which measured samples of the un cleaned air and of the air cleaned by a device under test are passed through filter papers.59 The ratio of the flow rates through the two filter, papers is adjusted during successive tests, until the resulting dust spots approach equality in density as shown by a photometer. The ratio of the flow rates is then indicative of the effectiveness of the cleaner in arresting dust. A statement of an air cleaner's efficiency by any test method, is meaningless unless the test dust is specified. Other instruments for determining gaseous and particulate air con taminants are described in industrial hygiene literature.57 61 62163 Sound and Vibration Measurements . . Approximate measurements of sound intensity can be made by aural methods. The ear is used to compare the measured noise with sounds of known strength. Electrical devices, in which the ear plays no part, furnish the most satis factory means of measuring noise intensities. The sound-meter consists essentially of a microphone coupled to an amplifier designed with an ear-like response. The output of the microphone is read on a sensitive direct current millia.Tnmet.er graduated to read directly in decibels. Instruments of this type, if connected with suitable band pass filters, can be used to study the intensity of the sound over its entire range of frequencies. Electrical instruments are available for measuring the frequency, ampli tude and acceleration of a vibrating mass. They are usually more con venient and accurate than the vibrating reed tachometer, the seismic type displacement meters or-the accelerometers which, can also be .used for this purpose. Sound level meters are discussed in several text books64- " and standards.66 REFERENCES Standard Code for Testing and Rating Steam Unit Heaters, adopted January, 1930, by A.S.H.V.E., revised 1950. ., AJ3.H.V.E. Standard Code for Testing and Rating Steam Unit Ventilators (A.S.H.V.E. Transactions Vol. 35, 1933, p. 25), adopted June, 1932. < A^.RU. Standard Methods of Rating and Testing Air Conditioning Equipment, A.S.R.E. Circular No. 13. ... A Survey of Testing Methods and Rating Limits for. Domestic Heating Devices, by. R. S. Dill (AJS.H.VJ3. Transactions, Vol. 51, 1945, p. 185). For a comprehensive treatment of temperature measurement the reader is referred to .Temperature,- Its Measurement and Control in Science and Industry, a symposium sponsored by the 'American Institute of Physics and published by Reinhold Publishing Corp. Errors in the Measurement of the Temperature of Flue Gases, by P. Nicholls&nd W. E. Rice (A.S.H.V.E Transactions, Vol. 35,1929, p. 473). ' J Temperature Measurement (AJSMJS. Power Test Code, Part 3). Investigation of Warm Air Furnaces and Heating Systems, by A. C. Willard, A. P. Krais and V. S. Day, {Illinois Engineering Experiment Station, Bulletin No. 120). Instruments and Measurements 1039 Measuring Heat Transmission in Building Structures and a Heat Transmission Meter, by P. NichoQs (A.S.H.V.E. Transactions, Vol. 30,1924, p. 94). io Parallel-Connected Thermocouples for the Testing of Gas Appliances, by Walter B. Kirk and George J. Pacanovsky (Gas, September, 1939, p.'51). u iTnarican Standard for Indicating Pressure and Vacuum Gages, Round Dial Type, with Elastic Pres sure Chamber, B. 40.1 1939-(Amricon Standards Association). n standard Test Code for Centrifugal and Axial Fans, 1938 (AJ5M.VJ3. and N.AJFJd.) published by NJAJP-M. as Bulletin No. 110. u Fan Engineering, Buffalo Forge Company, 5th Edition, p. 165. i* Illinois Micromanometer (University of Illinois, Engineering Experiment Station Bulletin No. 120, p.91). t*The Weathertightness of Rolled Steel Windows, by J. E. Emswiler and W. C. Randall (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 527). > Pressure Measurement (AJ5.MJ2. Power Test Code 1936, Part 2, Chapter 2). n The Measurement of Static Pressure, by C. J. Fechheimer (Mechanical Engineering, August, 1927). is Pgychrometric Tables for Vapor Pressure, Relative Humidity and Temperatures of the Dew-Point (U. S. Department of Agriculture, Weather Bureau, Washington, D. C.). i* For fr*1^TM*** data refer to Fluid Meter Reports, Parts 1--1937,2--1931, and 3--1933 (American Society of Mechanical Engineers). so Technical Notes No. 546 (National Advisory Committee for Aeronautics, November, 1935). ti The Characteristics of Double Pitot Tubes, by F. R. Ingram, E. Diez-Canseco and L. Silverman (A.S.H.VJ3. Journal Section, Heating, Piping and Air Conditioning, November, 1942, p. 708). ts Discharge Coefficients of Square Edged Orifices for Measuring the Flow of Air, by H. S. Bean, E. Buck ingham and P. S. Murphy (Bureau of Standards Journal of Research, Vol. 2, 1929, p. 561). o plow Measurement by Nozzles and Orifice Plates (A.S.MJ5. Power Test Codes, Chapter 4 of Part 5, 1940). , m Air Flow Measurement in the Laboratory, by D. D. Wile (Refrigerating Engineering, June, 1947, p. 515) u A.S.H.VJE. Research Report No. 1204--Entrainment and Jet-Pump Action of Air Streams, by. G. L. Tuve, G. B. Priesterand D. K. Wright, Jr. (AJ5.H.VJE. Transactions, Vol. 48,1942, p. 241). * AJS.H.VJ3. Research Reports Nos. 857,911 and 966--Measurement of the Flow of Air Through Reg isters and Grilles, by L. E. Davies (AJS.H.V.E. Transactions, Vol. 36,1930, p. 201, Vol. 37,1931, p. 619, and Vol. 39, 1933, p. 373). A.S.H.Vil. Research Report No. 1162--Air Flow Measurements at Intake and Discharge Openings and Grilles, by G. L. Tuve and.D. K. Wright, Jr. (A.S.H.VJ2. Transactions, Vol. 46, 1940, p. 313). * AJS.H.VJE. Research Report No. 1092--The Flow of Air Through Exhaust Grilles, by A. M. Greene, Jr. and M. H. Dean (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 387). if AJS.H.VJE. Research Report No. 936--Investigation of Air Outlets in Class Room Ventilation, by G. L. Larson, D. W. Nelson and R. W. Kubasta (AJ3.H.V.E. Transactions, Vol. 38,1932, p. 463). *o A.S.H.V.E. Research Report No. 1076--Air Distribution From Side Wall Outlets, by D. W. Nelson and D. J. Stewart (A.SJI.VJ3. Transactions, Vol. 44, 1938, p. 77). ti Measuring Air Flow, by G. L. Tuve (Heating, Piping and Air Conditioning, December, 1941). **AJS.H.V.E. Research Report No. 1140--The Use of Air Velocity Meteia, by G. L.Tuve, D. K. Wright, Jr. and L. J. Seigel (A.S.H.V.B. Transactions, Vol. 45, 1939, p. 645). a Temperature, Humidity and Air Motion Effects in Ventilation, by O. W. Armspach and Margaret Ingels (A.S.H.V.E. Transactions, Vol. 28, 1922, p. 103). u A.S.H.VJ3. Research Report No. 1165--Development of Instruments for, the Study of Air Distribu tion in Rooms, by A. P. Kratz, A. E. Hershey and R. B. Engdahl (A.S.H.V.E. Transactions, Vol. 46,1940, p. 351). m Development of Testing Apparatus for Thermostats, by D. D. Wile (AJS.H.VJ3. Transactions, Vol. 42, 1936, p. 349). u The Heated Thermometer Anemometer, by C. P. Yaglou (Journal Industrial Hygiene and Toxicology, Vol. 20, October, 1938, No. 8). A Simple Heated-Thermocouple Anemometer, by H. B. Nottage (AJ3.H.V.E. Journal Section, Heating, Piping and Air Conditioning, Vol. 22, September 1950, p. 146). "A.S.H.V.E. Research Report No. 959--Indices of Air Change and Air Distribution, by F. C. yrmighton and J. L. Blackshaw (A.SJ0LVJ). Transactions, Vol. 39, 1933, p. 261). s Measurement of Ventilation Using Tracer Gas Technique, by J. B. Dick (AJ5.H.V.E. Journal Section, Heating, Piping and Air Conditioning, May 1950, p. 131). The Temperature of Evaporation, by Willis H. Carrier (A.S.H.VJE. Transactions, Vol. 24,1918, p. 25). i Psychrometric Tables for Vapor Pressure, Relative Humidity and Temperatures of the Dew-Point (U. S. Department of Agriculture, Weather Bureau, Washington, D. C.). A Review of Existing Psychrometric Data in Relation to Practical Engineering Problems, by W. H. Carrier and C. O. Mackey (A.S.MJS. Transactions, January, 1937, p. 33; Discussion AEMM. Transactions, August, 1937, p. 528). a Divided Flow Low Temperature Humidity Test Apparatus, by Arnold Wexler (National Bureau of Standards, Research Paper No. 1894). *4 Gas Analysis by Measurement of Thermal Conductivity, by H. A. Dayneg (Cambridge Press, 1933). ** Standard Method of Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate, adopted July, 1942, by A.S.H.V.E. (AJS.TM. Designation C177 - 42T). * Guarded Hot Plate Apparatus Complying With the Requirements of Section 4 of AE.TM. Method of Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate, AJ3.T.M. AJS.H.VJ3. Standard Test Code for Heat Transmission Through Walls (A.S.H.V.E. Transactions, Vol. 34, 1928, p. 253), adopted 1928. A.S.H.VJE. Research Report No. 685--Measuring Heat Transmission in Building Structures and a Heat Transmission Meter, by P. Nicholls (AJS.H.V.E. Transactions, Vol. 30,1924, p. 65). Instruments and Methods for Recording Thermal Factors Affecting Human Comfort, by C. P. Yaglou, A. P. Kratz and C.-E. A. Winslow (Year Book, American Journal Public Health, 86-37).