(The following PDF file is quite large, and the internet link moderately slow, so you may have to be patient for it to download) (Chapters 1 to 11, and 19) of "Laboratory Instruments, Their Design and Application" (1960) by A. Elliott and J. Home Dickson as an Adobe PDF file of the JPG images

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(Chapters 1 to 11, and 19) "Laboratory Instruments, Their Design and Application" by A. Elliott and J. Home Dickson (Second Edition revised, 1960)

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Title page

Title page [cont'd] and Preface to the Second Edition

PREFACE TO THE SECOND EDITION

THE demand for a second edition has given us the opportunity to revise the book very completely, correct some doubtful points, bring the matter up to date and add much new material. The chapter on properties of materials has been expanded to include a fuller account of plastic materials, in which field there have been important developments. The same chapter also introduces the subject of corrosion-resisting metals, and a complete new chapter has been added on the subject of corrosion in laboratory instruments. Personal experience has shown how troublesome corrosive agents may be in some laboratories, and it is hoped that this chapter will be of value to many.

Some new figures have been prepared to amplify the section on cross-spring pivots, which are finding new applications as they become better known, and additional figures have been added to illustrate the subject of errors in instruments. The appendix on optical crystals has been enlarged into a chapter with the latest possible information on the refractive index of materials useful in infra-red spectrometry. A complete new section on radiation has necessitated another new chapter which includes the section on photometry. Some new matter has been added on colour vision, to the diagrams of photographic lenses, and in the chapter on photography. Photographic resolution has been treated much more fully.

Some new information on glass protection against radiation hazards which arrived too late for incorporation in Chapter 12 has been added as Appendix IV.

As in the first edition, we have confined ourselves almost wholly to mechanical and optical matters, since any adequate treatment of electronic instruments would have made the scope of the book much too wide.

The revisions and additions have been prompted by the many helpful criticisms and suggestions of friends and colleagues to whom we are very grateful. Research units and establishments in many parts of the world and many firms have also suggested improvements

Preface to the Second Edition [cont'd] and Preface to the First Edition

which we have endeavoured to include and have provided us with much interesting new matter. We hope that this new edition will prove to be a considerable improvement on the first edition.

A. ELLIOTT
J. HOME DICKSON

PREFACE TO THE FIRST EDITION

THE present-day trend towards specialisation is making it more difficult for students in Universities and Technical Colleges to obtain the wider general training which is so necessary for successful research work.

In any research organisation the worker is often called on to design and construct his own instruments or to guide others in their construction, and he finds his training inadequate to cover the many ramifications involved in this aspect of the work.

It is especially to provide some guide to these ancillary processes and components that this book has been written. The chief aim has been to present the principles on which good design is based, and many examples of the application of the principles have been given. No attempt has been made to cover the entire field of instrument design, but the authors have endeavoured throughout to show the interrelation of good design, material, and method of construction, so that the best results may be obtained with moderate or limited means.

The first few chapters deal with the properties of various materials and their treatment and use in the construction of instruments. A number of workshop processes are described and the accuracy attainable in the various processes is discussed. There is a chapter on the preparation of drawings for workshop use and their reproduction. Succeeding chapters are devoted to methods of construction to suit special requirements and in particular the kinematic design of instru- ments is treated at some length. Chapters on vibration insulation, sensitivity and methods of measurement follow.

Since optical instruments of many kinds and photography play such a large part in modern research work the remainder of the book is concerned with such instruments and methods. Chapters on glass and on the uses and working of glass are followed by a description of a number of optical instruments and devices. There are many tables and diagrams illustrating the uses of lenses, mirrors and prisms and there is much information which is not generally included in books on optics or in the normal college courses. Finally there is a chapter on the applications of photography and several appendices containing miscellaneous information.

Preface to the First Edition [cont'd] and Acknowledgements

In compiling such a book, based as it is on the accumulated experience of the authors, during many years of research work, there must necessarily occur many items of information collected from a number of sources. Copious references and acknowledgements have been made throughout the book and there has been added a collected list of acknowledgements but the authors must repeat here that they are indebted to many others whose names may not occur in these lists and we take this opportunity of thanking all those whose help, through the years, has made this book possible.

A. ELLIOTT
J. HOME DICKSON

Acknowledgements [cont'd]

Contents

Preface to Second Edition (Page v)

Preface to First Edition (Page vii)

Acknowledgements (Page ix)

1. GENERAL CONSIDERATIONS (Page 1)

2. THE ACCURACY ATTAINABLE IN MACHINING OPERATIONS (Page 4)

Nominal size, tolerance, limits, allowance. Limits of accuracy to be expected in turning. Plain milling. Surface grinding. Centre grinding. Lapping. Spinning. Location of holes with respect to other holes and to edges and surfaces.

3. PROPERTIES OF MATERIALS USED FOR GENERAL CONSTRUCTION OF INSTRUMENTS (Page 17)

Wood: pine, mahogany, teak, afrormosia, iroko, boxwood, plywood. Metals: wrought iron, mild steel, Case hardening: hard or carbon steel, Grades of Carbon Steel: Stabilization: Alloy Steels. Cast iron: grey cast iron, white cast iron, nodular or spherulitic graphite cast iron. Internal damping. Stainless steel and iron. Staintess cutlery steel. Austenitic steels, Iron-nickel alloys-"Invar". Copper alloys: cartridge brass, Munts metal, turning brass, clock brass, Admiralty gunmetal, porous bronze. Aluminium and aluminium alloys: aluminium, aluminium alloys, duralumin, Y-alloy, Hiduminiurn R.R.50, D.T.D. 424. General remarks on the use of light alloys. Corrosion-resistant metals (non-ferrous). Plastic materials: phenol formaldehyde resin, polymethyl methacrylate, polystyrene, polyethylene, polytetrafluorethylene, polyvinyl chloride, silicone elastomer. Materials for springs: elastic properties, steel, phosphor bronze, beryllium copper, fused silica.

4. CASTING AND JOINTING OF METALS (Page 56)

Casting, jointing, soldering and brazing. Welding: electric welding, flame welding, flame cutting. General observations on welding. Resin-bonded construction: Araldite Type L Cold-setting Araldite. Jointing by mechanical means: rivets, screws, locking of screws and nuts. Relative advantages of cast and built-up work.

5. PREPARATION OF DRAWINGS (Page 7l)

Materials for drawing. Assembly and detail drawing. Method of projection: types of lines, scale, sections, screw threads. Dimensions and tolerances. Reproduction of drawings.

6. CONSTRAINED MOTION AND CONSTRAINTS (Page 79)

Kinematic or geometric Design: degrees of freedom, motion of translation, body without freedom. General remarks on geometric design. Accuracy of performance of geometrically constrained mechanism. Modifications to geometric design. Constrained motion employing elastic deformation. The cross-spring pivot. Effect of large deflections: strips giving parallel motion. Springs and clamps.

7. THE MAGNIFICATION OF SMALL DISPLACEMENTS (Page 109)

Mechanical methods: lever magnification. Rolling cylinder and related methods. Parallel deformable strips. Ratchet and toothed wheels: dial gauges, liquid levels. Conditions affecting liquid levels, mounting of levels. Liquid levels for magnifying small movements. Magnification by optical methods: magnification by optical lever, observation of angular movement of light beams. Telescope and scale. The auto-collimator. Moir6 fringes. Interference methods. The thermal relay. Photo-electric relay. Electrical methods.

8. SENSITIVITY AND ERRORS OF INSTRUMENTS (Page 135)

Sensitivity of instruments. Errors. Systematic errors. Errors due to imperfections of the constraints. Errors of screws. Parallax error.

9. ISOLATION OF APPARATUS FROM DISTURBING INFLUENCES (Page 146)

Effect of disturbances on instruments. Means for reducing sensitiveness to disturbances. Isolating apparatus from mechanical disturbances. The Julius suspension. Millier's mounting. Haringx antivibration mounting. Methods of employing special properties of materials. Temperature variation.

10. DAMPING (Page 171)

Theoretical considerations. Best conditions for damping. Methods of applying damping forces.

11. TESTS FOR STRAIGHTNESS, FLATNESS AND SQUARENESS (Page 179)

Inclination of the surface. Light beam as straightness gauge. Dis- placement from material reference surface. Optically worked glass reference surface (interference method). Liquid reference surface. Standard reference surfaces. Tests for squareness. squareness tests for two flat surfaces, testing two rectilinear motions for squareness.

12. GLASS (Page 192)

Types of glass: window or sheet glass, plate glass, safety glass, fibre glass, chemical glass, optical glass. Optical plastics. Transmission and reflection. Absorption. Detection of defects in glass. Physical properties of glass: density, strength, hardness, elasticity, coefficient of expansion, specific heat, thermal conductivity, thermal endurance, electrical properties.

13. NATURAL AND SYNTHETIC OPTICAL CRYSTALS (Page 233)

Refractive indices of crystalline materials. Instruments.

14. THE WORKING OF GLASS (Page 248)

Cutting, sawing and drilling. Abrasives for glass working: grinding sands, emeries, carborundum, pure alumina (corundum), diamond powder, pumice stone, roughing, trueing and smoothing. Polishing powders: rouge, cerium oxide, white tripoli, putty powder. Trueing tools. Polishers. Making a polisher. Centring and edging. Cementing of glass parts. Cementing of glass to metals. The production of graticules.

15. LENSES, MIRRORS AND PRISMS (Page 270)

General remarks. Thin lenses. Combinations of leases. Spherical aberration. Coma. Astigmatism. Curvature. Distortion. Chromatic aberration. Stops, diaphragms and pupils. Magnifiers. Eye-pieces. Telescope objectives. Microscope objectives. Reflecting microscope objectives. Camera lenses. Condense:rs, Cylindrical lenses. Aplanatic systems: (i) ellipse, (ii) hyperbola, (iii) parabola, (iv) sphere. Lens-rnirror systems. Prisms. Specification of optical parts: plane mirrors, glass windows and filters, prisms, lenses.

16. OPTICAL INSTRUMENTS (Page 346)

The eye. Colour of light. Colour rendering. Defects of the eye. Telescopes. Microscopes. Projectors. Stereoscopic projection.

17. RADIATION AND PHOTOMETRY (Page 377)

Radiation. Thermal radiation. Laws of thermal radiation. Colour temperature. Sources of infra-red radiation. Radiation measurement. Photo-conductive devices. Photo-emissive cells. Photo-multipliers. Photo-voltaic cells. Transistors. Relative sensitivity of detector with any radiator. Ultimate sensitivity of radiation detectors. Photometry. Photometry of optical instalments. Photometric instruments. Some atomic and molecular constants.

18. PHOTOGRAPHY IN RESEARCH (Page 418)

The emulsion. Characteristic curve. Colour film. Exposure. Methods of obtaining increased speed. Grain. Resolution. Processing. Light sources. Exposure meters. Filters. Shutters. Lenses. Cameras. Infra-red and ultra-violet photography. Applications.

19. CORROSION IN INSTRUMENTS AND ITS PREVENTION (Page 469)

The general problem. Reduction by improving local conditions. Use of inhibitors in aqueous solution. Yapour-phase inhibitors. Use of suitable materials: bimetallic corrosion, corrosive chemicals. Protection by means of paints, lacquers and enamels. Epoxide resins for finishes. Silicone tinishes. Anti-corrosive finishes for metals (other than paints): zinc, cadmium, nickel, chromium. Various processes for protecting iron and steel. Chemical polishing of steel. Oxide coatings on aluminium and its alloys. Magnesium and its alloys. Polyethylene protective coatings on metals.

Appendix

I. COMPUTATION OF A CORRECTOR PLATE FOR A SCHMIDT CAMERA (Page 491)

II. NOTES ON RAY-TRACING (Page 495)

III. ANGULAR MEASUREMENT (Page 499)

IV. NUCLEAR RADIATION, PROTECTION AND STABILIZED GLASS (Page 501)

V. TABLE FOR USE WITH SAYCE RESOLUTION CHART (Page 504)

INDEX (Page 505)

CHAPTER 1

GENERAL CONSIDERATIONS

RECENT years have seen a great extension in the use of physical methods in widely differing fields. In all branches of industry, in medical and biological research and in the defence services such methods are used, while many who received their first training as chemists find themselves using the tools of the physicist during the greater part of their working time. The various needs of such workers are partly met by the output of the scientific instrument firms, but new fields of research demand new methods, and much routine test equipment is so specialised that it must be designed for a particular purpose. Some instrument manufacturers undertake the design and construction of special apparatus and in certain classes of work this is undoubtedly the best solution. It is, however, not always satis- factory, unless there is very close co-operation. In every research establishment, a considerable amount of equipment is made by the workshop, usually to the design or instructions of the research worker. It is chiefly to meet the needs of such cases that this book has been written, though it is hoped that it may be of use to the professional instrument designer as well. Apparatus for teaching purposes in universities and technical colleges is often of poor design, and not always suited to its purpose. In this field, too, the apprecia- tion of the principles of good design are important.

Good design will take into account the imperfections of current workshop practice and the limitations imposed by the properties of the materials available. For this reason, we have put these two sub- jects first and have tried to present a picture of what can be expected of a good workshop, and how design can keep the inevitable errors of performance within acceptable limits. The design of many com- mercial instruments is capable of considerable improvement in this respect, though the work of the best firms is above reproach. The subject owes much to the early work of Kelvin, Clerk Maxwell and Darwin, but has been greatly extended and ably expounded by the late Professor A. F. C. Pollard, who died while the first edition of this book was being written.

Since the eye is the organ chiefly used in accurate perception, the majority of instruments are made for visual observations. Accord- ingly, we have considered the properties and manufacture of optical components as well as the properties of the eye. In many instruments the optical parts may play only a subsidiary rble (often to provide an enlarged image for observation) but are nevertheless very im- portant.

World War II brought home to many academic scientists the importance of the human observer and his relation to the instruments he used. The services rightly insisted that an uncomfortable observer was an inefficient observer, and much attention was paid to comfort. Faulty observation in the laboratory is not deadly as, for instance, in the cockpit of a night fighter plane, but it should be avoided if possible, and instruments should not cause strain or fatigue. It is, however, difficult to reach this ideal at the first attempt, and usually re-design is needed to achieve the best results.

When the principles of sound design are understood, a good deal of work can be done on paper with the assurance that the instrument will function properly when made. Many instances arise, however, when it is impossible to visualise the arrangement and forecast how it will work. This is often the case when a mechanism depends on the action of springs, for instance. In such cases it often saves time if a rough model of such a part is made. Sometimes a " space model " of a part is useful. This is a model, usually made in wood, having the external dimensions of the actual instrument which it represents, but not capable of working. It is useful when the part has to be fitted in some larger assembly.

Optical arrangements are often set up in rough form, using simple components such as spectacle lenses, before the mechanical parts are designed. It is often found, contrary to expectation, that the mechanical parts of an optical instrument are the most difficult to design and make satisfactorily.

Opinions differ as to the extent to which apparatus constructed in the laboratory should be of a makeshift character when it is only to be used for a short time. If the apparatus is made with the least possible expenditure of work, it is true that workshop time may be saved, but a great deal of time may be wasted later by the experi- menter who has to try to make defective apparatus work. It usually pays to have research apparatus soundly constructed, and this is true of the smaller parts of research equipment such as mountings, stands, adjustable holders, etc.. as well as of the larger instruments. At the same time, it will be realised that nothing is gained by a super- the finish. and the condition of rnuch of the material surfaces used in research apparatus is of no importance whatever. This is hardly the case with apparatus used in teaching, for it seems that in many cases students produce better work if they feel that they are using good instruments. Elementary students are only able to judge the per- fbrniance of an instrument to a limited extent, and appearances count for something. For this reason, some attention may be given to finish as well as to function in apparatus for teaching. It is, however, useful to have apparatus in which the difference can be seen between those parts which require accuracy in manufacture and those which do not, provided that the difference is made clear.

Chapter 2: THE ACCURACY ATTAINABLE IN MACHINING OPERATIONS

Nominal size, tolerance, limits, allowance

Fig. 2.1: chief parts of intrument maker's lathe. The drive for the spindle at the left hand side is not shown. Work is held in a 3-jaw check

Fig. 2.2: Work supported between centres, driven by dog

Limits of accuracy to be expected in turning

Plain milling

Figure 2.3.: Chief parts of plain miller, showing flat face being milled on work. Motion is in direction OZ for this operation.

Surface grinding.

Fig. 2.4: Essentials of a surface grinder

Centre grinding

Lapping

Spinning

Location of holes with respect to other holes and to edges and surfaces

Table 2.1: Accuracy of Holes

References

General References

Chapter 3: PROPERTIES OF MATERIALS USED FOR GENERAL CONSTRUCTION OF INSTRUMENTS

Wood

Pine

Mahogany

Teak

Iroko

Plywood

Metals

Wrought iron

Mild Steel

Case Hardening

Hard or carbon steel

Table 3.1: Tempering of Carbon Steel

Grades of Carbon Steel

Stabilisation

Alloy steels

Cast Iron

Grey cast iron

White cast iron

Nodular or spherulitic graphite cast iron

Internal damping

Stainless Steel and Iron

Stainless cutlery steel

Austenite steels

Iron - Nickel alloys - "Invar"

Copper Alloys

Cartridge brass

Muntz metal

Turning brass

Table 3.2: Properties of Metals for Construction

Clock brass

Admiralty gunmetal

Porous bronze

Aluminium and Aluminius Alloys

Aluminium

Aluminium alloys

Duralumin

Y-alloy

Hiduminium R.R. 50.

D.T.D. 424

General remarks on the use of light alloys

Corrosion-resistant metals (non-ferrous)

Table 3.3: Corrossion Resistance of Some Metals

Plastic Materials

Phenol formaldehyde resin

Polymethyl methacrylate

Polystyrene

Polyethylene

Table 3.4: Properties of some plastics

Polytetraflourethylene (P.T.F.E.)

Polyvinyl chloride

Silicon elastomer

Materials for Springs

Elastic properties

Fig. 3.1: Typical endurance limit curves for Mallory 73 Beryllium Copper in reversed bending. Arrow heads indicate unbroken test pieces. (Mallory Metallurgical Products Ltd.)

Fig. 3.2: Tensile stress-strain curves for spring materials in strip form. (Mallory Metallurgical Products Ltd.)

Steel

Phosphor bronze

Fig. 3.3: Torsional stress-strain curves for spring materials in the form of 0.10 in. diameter wire. (Mallory Metallurgical Products Ltd.)

Beryllium copper

Table 3.5: Heat Treatment of Mallory 73 Beryllium Copper

Fig. 3.4: Elastic properties of fused silica fibres (Reinkober) : (a) Modulus of elasticity (old fibres); (b) Modulus of elasticity (etched fibres); (c) Modulus of torsion (old fibres); (d) Modulus of torsion (etched fibres)

Fused silica

Table 3.6: Strength of Silica Fibres

References

Chapter 4: CASTING AND JOINING OF METALS

Casting

Fig. 4.1: (a) Pattern from which a casting is to be made, and (b) Moulding box filled with sand, showing mould formed by removal of pattern.

Fig 4.2: Pattern and core required to make a casting with a hold right through

Jointing

Soldering and brazing

Welding

Electric Welding

Frame welding

Flame Cutting

General observations on welding

Resin-Bonded Construction

Araldite Type 1.

Table 4.1

Cold-setting Araldite

Table 4.2: Dimensions of Small Rivets (See Fig. 4.3) Data from British Specification 641, 1935)

Jointing by mechanical means

Rivets

Fig 4.3: Various rivets. The relative dimensions of rivets according to B.S.S. 641, 1935, are given in Table 4.2.

Screws

Fig. 4.4.: Types of screw heads and plain nuts

Fig. 4.5.: Use of taper pins to secure accurate location of a removable part. The counterbored holes are used wen screw heads must not project.

Fig. 4.6.: Hexagon socketed cap screw and wrench

Fig. 4.7.: Showing the use of socketed cap screws in a situation inaccessible to a screwdriver or spanner.

Locking of screws and nuts

Fig. 4.8.: Methods of locking screws and nuts. The Simmonds nut is self-locking.

Relative advantages of cast and built-up work

References

Chapter 5: PREPARATION OF DRAWINGS

Material for drawing

Assembly and detail drawings

Fig. 5.1.: Relative positions of various views of an object using British standard projection (B.S. 308: 1943)

Method of projection

Fig. 5.2.: Relative positions of views in American projection. (B.S. 308: 1943)

Types of line

Scale

Sections

Screw threads

Types of Lines

Fig 5.3: Types of line. (B.S. 308: 1943)

Fig 5.4: Section in one plane not on centre lines. (B.S. 308: 1943)

Fig 5.5: Section in one plane along centre line. (B.S. 308: 1943)

Fig 5.6: Section in two planes. (B.S. 308: 1943)

Fig 5.7: Superimposed cross sections. (B.S. 308: 1943)

Fig 5.8: Cross section places to one side (B.S. 308: 1943)

Fig 5.9

Fig 5.10

Fig 5.11.

Fig 5.12.

Fig 5.13.

Fig. 5.9-5.13: Conventional representation of screw threads. (B.S. 308: 1943)

Dimensions and tolerances

Fig 5.14: Method of indicating dimensions and tolerances

Additional instructions

Fig 5.15: Conventional "breaks" (B.S. 308: 1943)

Reproduction of drawings

Reference

Chapter 6: CONSTRAINED MOTION AND CONSTRAINTS

Kinematic or Geometric Design

Degrees of freedom

Fig 6.1: Kinematic slide allowing movement of a carriage in a straight line.

Fig 6.2: Kinematic design employing cylindrical surfaces as guides. Such surfaces can be accurately made.

Fig 6.3: Kinematic slide. The spheres are fixed to the carriage.

Fig 6.4: Carriage of Wickman gauge, giving very free motion by the use of rolling spheres D and E.

Fig 6.5: Symmetrically opening slit for optical instruments. Rolling motion of spheres is employed. The figure is drawn in American projection; the side view shows the end plates removed.

Fig 6.6: Simple kinematic arrangement giving rotation about a vertical axis.

Fig 6.7: Micrometer movement for rotating a vertical shaft, using kinematic principles.

Fig 6.8: Arrangement for rotating carriage round an arc of large radius.

Fig 6.9: Rotatory motion using rolling spheres.

Body without freedom

Fig 6.10: Accurate locatino of removable part obtained with vee-grooves for ball-ended feet.

Fig 6.11: Adjustable mirror mount or levelling table.

General remarks on geometric design

The accuracy of performance of a geometrically constrained mechanism

Modifications to geometric design

Fig 6.12: Semi-kinematic element, with bearing surfaces of appreciable area.

Fig 6.13: Semi-kinematic slide of Sartorius microtome

Constrained motion employing elastic deformation

Fig 6.14: Strip hinge, giving rotation about a fixed axis and using elastic deformation

The Cross-Spring Pivot

Effect of large deflections

Strips giving parallel motion

Fig. 6.15.: Stiffness of a symmetrical cross-spring pivot consisting of two pairs of spring strips intersecting at 90 deg. at their mid-points. Width of each spring = 1/4 in. (Nickols and Wunsch(10).) (Crown Copyright Reserved.)

Fig. 6.16.: Shift of axis of rotation of symmetrical cross-spring pivot consisting of two pairs of spring strips intersecting at 90 deg. at their mid-points. (Nickols and Wunsch(10).) (Crown Copyright Reserved.)

Fig 6.17: Use of spring strips to give motion in a straight line (for small displacements)

Springs and clamps

Fig 6.18: Good (a) and bad (b) forms of springs for holding moving parts in contact with their guides.

Fig 6.19: Spring washer for preventing backlash in screw and nut

Fig 6.20: Spring-loaded plunger for adjusting screw

Clamps

Fig 6.21: Self-adjusting foot for clamping screw.

Fig 6.22: Retort stand boss with springs to allow regulation of clamping force

Fig 6.23: Clamping arrangement for plane mirror (Hilger spectrometer)

Fig 6.24: Clamping of plane mirror in Perkin-Elmer spectrometer

References

Chapter 7: THE MAGNIFICATION OF SMALL DISPLACEMENTS

Mechanical Methods

Lever Magnification

Fig 7.1: Lever using cross-spring pivot to give rotation about a fixed point and hence to magnify plunger movement by a constant factor.

Rolling cylinder and related methods

Fig 7.2: Differential roller mechanism

Parallel deformable strips

Fig 7.3: Magnification of movement by use of deformable perallel strips

Ratchet and toothed wheels. Dial gauges

Fig 7.4: Dial gauge (Mercer). A similar gauge is shown in use in Fig 11.7.

Liquid levels

Fig 7.5: Principle of liquid level.

Conditions affecting liquid levels

Mounting of levels

Liquid levels for magnifying small movements

Magnification by Optical Methods

Fig 7.6: Fiduciary mark and scale, as used in Watts level.

Magnification by optical lever

Fig 7.7: Optical lever for high magnification (Dye)

Observation of angular movement of light beams

Fig 7.8: Lamp and scale to read deflections of optical lever

Fig 7.9: Contours of geometrical and of diffraction images of a narrow wire

Fig 7.10: Observation of mirror deflection by means of telescope and scale.

The Auto-collimator

Fig 7.11: Auto-collimating telescope for observing mirror deflection. If no condensor is used between lamp and graticule, a frosted bulb should be used to illuminate the required field of view.

Moire fringes

Fig 7.12: Moire fringes for superposted gratings

Interference methods

Fig 7.13: Arrangements for viewing interference fringes formed in thin air film between two semi-reflecting surfaces.

Fig 7.14: Arrangement using parallel light to produce interference fringes between well-separated surfaces.

The thermal relay

Fig 7.15: Thermo-couple (Moll and Burger for thermal relay)

Photo-electric relay

Fig 7.16: Arrangement of optical parts in photo-voltaic relay.

Fig 7.17: Grids for more sensitive photo-voltaic relay.

Fig 7.18: Photo-voltaic arrangement with feed-back (Preston) (optical arrangement not shown, but similar to Fig. 7.16)

Electrical Methods

References

Chapter 8: SENSITIVITY AND ERRORS OF INSTRUMENTS

Sensitivity of instruments

Fig 8.1: Suspended system of Moll galvanometer

Errors

Systematic Errors

Errors due to imperfections of the constraints

Fig 8.2: Illustrating errors introduced by lack of straighness of constraints.

Errors of screws

Fig: 8.3: Plain thrust bearing in which the faces are not perpendicular to the axis of rotation.

Fig 8.4: Ball ended strut for coupling two colinear movements

Parallax error.

Fig 8.5: Use of mirror to avoid parallaz error.

Fig 8.6: Arrangement for projecting virtual image of illuminated pinhold on object to be measured, so avoiding parallaz errors.

References

Chapter 9: ISOLATION OF APPARATUS FROM DISTURBING INFLUENCES

Effect of disturbances on instruments

Fig 9.1: Rigid body suspended by single fibre

Fig 9/2: Rigid body held between stretched fibres

Means for reducing sensitiveness to disturbance

Isolating apparatus from mechanical disturbances

The Julius suspension

Fig 9.3: Julius anti-vibration suspension

Table 9.1: Damping of Pendulum

Muller's mounting

Fig 9.4: Muller's anti-vibrational support

Haringz anti-vibration mounting

Fig 9.5: Diagram (a) and frequency characteristic (b) of an undamped, vibration-free system.

Fig 9.6: Diagram (a) and frequency characteristic (b) of a vibration-free system with "relative" damping.

Fig 9.7: Diagram (a) and frequency characteristic (b) of a vibration-free system with "absolute" damping.

Fig 9.8: Vibration-free system with auxiliary mass M.

Fig 9.9: Frequency characteristic of the system shown in Fig. 9.8 for the two extremes of damping with k= infinity and k=0.

Fig 9.10: Frequency characteristic of an undamped system (curve 1), a system with auxiliary mass and "optimum" parameters chosen for u = 0.5 (curve 2) and a system with relative damping (curve 3). It is assumed that the total mass and also the rigidity of the spring c is the same in all three systems. Further, for curve 3 the damping was the same in all three systems. Further, for curves 3 the damping was so chosen that the maximum amplitude ratio is the same as in case 2.

Fig 9.11: The decay of the free vibrations after a given initial displacement for a system according to Gif. 9.8a and u = 0.5 and the optimum parameters p = 0.5 and q = 0.62.

Fig 9.12: Three different arrangements for making an apparatus vibration-free where multi-dimensional disturbing vibrations exist. The mounting are all symmetrical with respect to two perpendicular vertical planes.

Fig 9.13: Model of vibration-free mounting with auxiliary mass.

Fig 9.14: Example of a vibration-free mounting. The dimensions are 60 x 60 x 15 cm. ; its weight is 110 kg. The two plates a and b together form the main mass. They are connected by twelve rods c. The main mass rests upon four helical sprigs d. The auxiliary mass e is coupled to themain mass by eight springs f. The cup g is one of four damping elements.

Methods employing special properties of materials.

Fig 9.15: "Silentbloc" anti-vibration support, using rubber (shown black) bonded to metal.

Fig 9.16: Anti-vibration support using inflated rubber tyres (Gehrcke and Voight)

Temperature variation

Fig 7.19: Toluene thermostat with large surface for air temperature control

General Reference

References

Chapter 10: DAMPING

Theoretical considerations

Fig 10.1: Damped harmonic motion

Best conditions for damping

Fig 10.2: Damped harmonic motion in neighbourhood at first minimum (on large scale). n=1/2

Methods of applying damping forces

Fig 10.3: Variation in viscosity with temperature for some fluids suitable for damping. The full lines show curves for silicones, the broken curves refer to hydrocarbon oils. (Dow Corning Corporation)

Fig 10.4: Oil damping for the movement of a pen recorder.

Fig 10.5: Air damping arrangement on a chemical balance

Reference

Chapter 11: TESTS FOR STRAIGHTNESS, FLATNESS AND SQUARENESS

Inclination of the surface

Fig 11.1: Use of optical lever for measuring flatness of surface

Fig 11.2: Curvature of surface revealed by astimatism

Light beam as straightness gauge

Displacement from material reference surface

Optically worked glass reference surface (interference method)

Fig 11.3: Interference bands formed between flat and test object.

Liquid reference surface

Fig 11.4: Method of using liquid reference surface for checking flatness of plate. The micrometer is electrically insulated from the mercury cup.

Standard reference surfaces

Fig 11.5: Checking surface plate against straight-edge by means of dial gauge.

Tests for Squareness

Squareness tests for two flat surfaces

Fig 11.6: Standard square (to be replaced by test piece) on surface plate with dial gauge on kinematic slide.

Fig 11.7: Checking a square whose opposite sides are known to be accurately parallel, be reversal through 180 deg.

Fig 11.8: Use of auto-collimating telescope in test for squareness.

Testing two rectilinear motions for squareness

References

Chapter 19: CORROSION IN INSTRUMENTS AND ITS PREVENTION

The general problem

Reduction by improving local conditions

Use of inhibitors in aqueous solution

Vapour-phase inhibitors

Table 19.1: Saturation Vapour Pressures (in mm. Hg)

Use of suitable materials

Bimetallic Corrosion

Table 19.2: Degree of Corrosion at Bimetallic Contacts

Table 19.2: Notes

Corrosive chemicals

Protection by means of paints, lacquers and enamels

Epoxide resins for finishes

Epoxide Ester REsins

Epoxide Resins Cross-Linked with Phenolic or Amino Resins

Epoxide Resins CRoss-LInked with Amines

Silicon finishes

Anti-corrosive finishes for metals (other than paints)

Metallic Coatings

Zinc

Cadmium

Nickel

Chromium

Various processes for protecting iron and steel

Chemical polishing of steel

Oxide coatings on aluminium and its alloys

Magnesium and its alloys

Polyethylene protective coatings on metals

References

INDEX

ABERRATIONS

• astigmatic, 282--4
• chromatic, 286-8
• coma, 281-2
• effect of lens shape on, 283
• effect on image, 299
• spherical, 280

• of centre grinding, 13
• of geometric constraints, 90 -91
• of holes, 16
• of lathe turning, 9
• of milling, 11
• of squares (testing), 187--91
• of surface grinding, 13
• of surface plate (tosting), 179--87

• refractive index, 242

• of magnesium, 489

• anodic oxidation, 488-9
• metallic coatings, 483-6
• oxide coatings (iron), 486-7
• paints, etc., 478-83
• polyethylene coatings, 489-90

• Gehrcke and Voigt, 164 3
• Haringx, 155-63
• Julius, 151-3
• Miller, 153-5

• refractive index, 236, 244

• used in testing, 182

BACK CENTRE, USC Of in turning, 7-8
Back-lash, prevention of, 104
Bakelite, 38
Balancing of galvanometer, 149
Balls, accuracy of, 85
Barium fluoride, 235

• refractive index, 242, 246

• physical properties, 51-53

• cartridge, 29
• clock, 31
• physical properties, 31
• turning, 30

Brazeing, 58-59
Brewster's law, 211
Briggs, H. B., 246
Brightness (Luminance)

• apparent, 400
• borrowed, 404

CADMIUM COATINGS, 484
Cadmium fluoride, refractive index, 242
Cadmium sulphide cell, 386
Caesium bromide, 235

• refractive index, 236, 242, 245

• refractive index, 201, 236, 242, 243

• index, 242, 243

• diagrams of, 329-33
• table of, 334-7

• high speed, 457-8, 463, 466

• physical properties, 30

• diagram, 354
• film, 424, 426
• rendering, 356, 426
• temperature, 350, 382-3

• glass, 231
• metals, 30
• plastics, 43

DAMPED HARMONIC MOTION, 172-4
Damping

• best condition for, 174-5
• forces, 175-8
• internal, 25
• of instruments, 171-8
• of vibrations, 152-3

• use of, 186 -8

• for glass cutting, 248--50
• powder, 257
• refractive index of, 236, 242
• tools, 9

• reducing effect of, 149-65

ECLAIR COMPANY, 462
Edging lenses, 263
Elastic deformation, 95-102
Elasticity

• of glass, 230
• of metals, 30
• of plastics, 42

• of glass, 230-1
• of metals, 30
• of plastics, 42

FABRY-PEROT INTERFEROMETER, 129
Fastax high speed camera, 463
Fatigue in photo-cells, 132
Fechner fraction, 349
Fechner's law, 349
Fernico, 29
Fibre glass, 196-7
Fibres, fused silica, 53
Film speeds, 418, 421-7, 464--5
Films, non-reflecting, 211-12, 306, 461
Filters for mercury lines, 453, 454
Filters for photography, 447-54
Filters, interference, 214-18
Filters, testing, 227
Firth-Vickers Ltd., 30
Fizeau, H., 126
Flame cutting and welding, 60
Flatness