1、UDC 681.2 : 53.085.4 : 621.31 7.7.085.3/.4 DEUTSCH E N O R M January 1991 1 I Basic principles for the design of line scales and pointers I I DIN I 43790 1 / Grundregeln fr die Gestaltung von Strichskalen und Zeigern The field of application of this standard is not covered elsewhere in regional or i
2、nternational standards In keeping with current practice in standards published by the International Organization for Standardization (/SO), a comma has been used throughout as the decimal marker. Content Page Page 1 Scope and field of application 1 8 Pointer . . 1 9 Basic scale designs . nsions and
3、principles of scale graduation 3 Appendix A 4 Calculation of scale geometry . 5 12 Appendix B 5 Reading distances . 5 Standards referred to 13 6 Graduation and num 5 7 Recommendations on scale design . 6 Index . . 14 1 Scope and field of application This standard specifies basic rules for the design
4、 of line scales and pointers. These rules do not cover length measuring devices which also embody material measures and are subject to special requirements (e.g. graduated steel rules for inspection purposes as specified in DIN 865). Scales as dealt with in this standard comprise linear and non-line
5、ar single and multiple range scales which may be set out as straight, sector, or quadrant scales in horizontal or vertical alignment, or as full circular scales. When scales are to be constructed for measuring, testing and control instruments, even in those cases where modern technology is to be use
6、d for the display, due consideration must always be given in their design to the laws and limits of visual perception in order to minimize the errors of observation and interpolation.The implementation of the design crite- ria given here for line scales and pointers for use with different types of i
7、nstrument and for various applications will be the subject of separate standards. Nominal range 2 Concepts -4 cl I Measuring range II Major scale mark Notional mark for interpolation I/ Scale numbering o/ 50 Scale division I -t-r- I Numbering base Scale graduation Auxiliary. scale r Figure 1. Nomenc
8、lature -I Continued on pages 2 to 14 DIN 43 790 Eng/. Price group 7 ith Verlag GmbH, Berlin, has the exclusive right of sale for German Standards DIN-Normen). 09.91 Sales No. O110 Page 2 DIN 43790 2.1 Scale ranges and their identification 2.1.1 Nominal range The nominal range is the set of values of
9、 a measurand for which a measuring instrument gives values within that scale range at a particular setting of its controls. *) Note. The nominal range is normally stated in terms of its 2.1.2 Measuring range The measuring range of an indicating measuring instru- ment is the set of values of a measur
10、and for which the limits of error specified or agreed for that instrument are not to beexceeded (quoted from DIN2257 Part 1, November1982 edition). Note. If nominal range and measuring range are not coincident, design of the scale shall be based on the nominal range. lower and upper limits. 2.1.3 Me
11、asuring span The measuring span is the difference between the mini- mum and maximum scale values of the measuring range (quoted from DIN 2257 Part 1). 2.1.4 Nominal span The nominal span is the difference between the two limits of the nominal range. Example: nominal range: -lOV to +1OV; nominal span
12、: 20V. 2.2 Line scale, index 2.2.1 Lhe scale A line scale is a sequence of marks on a dial. The marks forming the scale may be numbered. As a rule, the number- ing will correspond to the units of measurement concerned (quoted from DIN 2257 Part 1). 2.2.2 Scale division Scale division is the part of
13、a scale between any two successive scale marks. *) 2.2.3 Scale spacing The scale spacing is the distance between any two succes- sive scale marks measured along the same line as the scale length; it is expressed in units of length or angle. *) 2.2.4 Scale graduation Scale graduation consists of a nu
14、mber of marks which enable thevalue of a measurand to be established from the position of the index (e.g. pointer) of a measuring instru- ment relative to them. 2.2.5 Scale interval The scale interval is the difference between the scale values corresponding to two successive scale marks.*) It is exp
15、ressed in the units marked on the scale. 2.2.6 Scale length The scale length is the length of the straight or curved line running between the first and the last scale marks and passing through the centres of all the shortest scale marks. It is expressed in units of length. Note. If a measuring instr
16、ument has more than one scale, each has its own scale length. As a rule, the longest scale is deemed to be the scale length of the instru- ment concerned. 2.2.7 Scale mark base The scale mark base is the actual or notional reference line from which one end of all scale marks emanates. 2.2.8 Numberin
17、g base The numbering base is the notional line on which the num- bers stand. 2.2.9 Scale numbering The scale numbering is the set of numbers that is co- ordinated with the scale marks. 2.2.10 Linear scale A linear scale is one in which each scale spacing is related to the corresponding scale interva
18、l by a constant factor. Note. A linear scale having constant scale intervals is also referred to as a regular scale. 2.2.1 1 Non-linear scale A non-linear scale is one in which each scale spacing is related to the corresponding scale interval by a factor that is not constant throughout the scale. No
19、te. Some non-linear scales have special designations, such as logarithmic scale or square-law scale. 2.2.12 Index An index is the fixed or movable part of an indicating device whose position with reference to the scale marks serves to define the value of a given reading. 2.3 Scale graduation and des
20、ign 2.3.1 Scale graduation 2.3.1.1 Fine graduation Fine graduation is used for precision tasks (close reading) where optimal conditions must be provided in terms of lighting, reading distance, and the time available for read- ing. 2.3.1.2 Coarse-fine graduation Coarse-fine graduation is used for ind
21、ustrial measurement applications (reading from two defined distances). The ba- sic layout of the scale equals that of the fine graduation. 2.3.1.3 Coarse graduation i) Coarse graduation is used for applications where readings are to provide approximate information at a glance, and where difficult co
22、nditions in terms of lighting, reading distance and the time available for reading may be assumed. 2.3.2 Design 2.3.2.1 Single scale A single scale is one that is set out on a notional scale mark base. 2.3.2.2 Dual scale A dual scale consists of two scales lying on opposite sides of an actual scale
23、mark base. 2.3.2.3 Auxiliary scale A scale is referred to as an auxiliary scale if the actual measurand is not identical with the input quantity and both measurand and input quantity are to be displayed on the same scale. 2.3.2.4 Multiple scale A multiple scale consists of a number of scales set out
24、 one above the other. *) Quoted from International Vocabulary of Basic and 1) Coarse scales are not suitable for interpolation. General Terms in Metrology. DIN 43 790 Page 3 2.3.2.5 Sequential scale A sequential scale consists of a number of scales arranged in series. 2.3.2.6 Single unit division In
25、 single unit division, the scale interval corresponds to the unit of the measurand or to decimal multiples or fractions of the same. 2.3.2.7 Two unit division In two unit division, the scale interval corresponds to twice the unit of the measurand or to decimal multiples or fractions of the same. 2.3
26、.2.8 Five unit division In five unit division, the scale interval corresponds to five times the unit of the rneasurand or to decimal multiples or fractions of the same. 2.4 Interpolation and resolution 2.4.1 Interpolation Interpolation involves establishing the value of the meas- urand by a notional
27、 division of the space between two consecutive scale marks in accordance with the required interpolation mode and the assignment of the index to the next visible or notional scale mark (interpolation by eye),as the position of an index is not always coincident with a scale mark. 2.4.2 Interpolation
28、mode The interpolation mode is the method selected for dividing the space between two consecutive scale marks. The following interpolation modes are to be distinguished: a) interpolation into halves of a scale division (two inter- polated divisions), used for single, two and five unit divisions: . b
29、) interpolation into quarters of a scale division (four inter- polated divisions), used for two unit division; c) interpolation into fifths of a scale division (five interpo- lated divisions), used for single and five unit divisions; d) interpolation to tenths of a scale division (ten inter- polated
30、 divisions), used for single unit division. 2.4.3 Interpolated divislon The interpolated division is the estimated fraction of a scale division. 2.4.4 Resolution The resolution is the smallest change in the measurand cor- responding to an interpolated division that can be read on the scale,expressed
31、 in the unit of the measurand (absolute resolution) oras a percentage of the nominal span (relative resolution). 3 Minimum dimensions and principles of scale graduation The following specifications refer to minimum dimensions. Where required for a given application (e.g. to allow for such factors as
32、 pointer travel and case size), or to ensure com- patibility with adjacent scales, the dimensions shall be increased proportionally. 3.1 Shape of scale marks All scale marks shall be straight, square-edged, clean cut and with opposite faces parallel. The ends of the scale marks may be rounded or squ
33、are, depending on the manu- facturing method used. To facilitate reading of the scale, some scale marks are to be emphasized by elongation. In the case of scales with fine graduation, all scale marks shall be of equal thickness. The upper half of the major scale marks of scales with coarse-fine grad
34、uation (.e. the half furthest from the scale mark base) shall be drawn thicker so as to facilitate reading of the scale from two reading distances. For scales with coarse graduation,either all scale marks may be drawn uniformly thick orthe minor, intermediate and major scale marks may be drawn in di
35、fferent thicknesses. 3.1.1 Fine graduation b I a Scale spacing b Thickness of scale mark Figure 2. 3.1.2 Coarse-fine graduation =2,5b 11 12 13 II Minor scale mark Intermediate scale mark Major scale mark Ill Figure 3. Page 4 DIN 43 790 3.1.3 Coarse graduation Figure 4. 21.7 b II -i1- lilllltllill Fi
36、gure 5. 3.2 Scale spacing The minimum scale spacing is to be calculated on the basis of the reading distance and the interpolation, using the following equation: (1) amin - 0,0007. d. n where a is the scale spacing; 0,0007 is a factor corresponding to an observation angle of 2,4 minutes of arc; d is
37、 the reading distance; n is the number of interpolated divisions within a scale division. Scale spacing of less than 1 rnrn should be avoided in prac- tice. Under difficult reading conditions, ami, shall be multi- plied by a factor of at least 2. Note. For scales with interpolation into tenths, ami,
38、 may be reduced by half. 3.3 Thickness of scale marks The minimum scale mark thickness is to be calculated from the following equation: bmin = 0,08 ami, (2) where amin is the minimum scale spacing. The maximum scale mark thickness,b,is obtained as 0.2 a for interpolation into quarters and fifths (3)
39、 and as 0.12 a for interpolation into tenths (4). 3.4 Length of scale marks The minimum length ofthe minorscale marks shall be equal to the minimum scale spacing, .e. li min = amin (5) In the case of interpolation into quarters, fifths, or tenths, the final scale spacing a shall be used for amin. Th
40、e following equations apply for the length of the inter- mediate (/*) and the major (13) scale marks: 12 = 15 * 11 (6) l3 = 2.2, (7) Note. For 11, the final dimension selected shall be entered. 3.5 Character height The minimum height of charactersshall be calculated using the following equation: hmi
41、n = 0,0035 d (8) where d is the reading distance. Note. The factor 0,0035 corresponds to 12 minutes of arc. 3.6 Lettering style The following lettering styles shall be given preference: a) lettering as specified in DIN 1451 Parts 3 and 4 (cf. Explanatory notes); b) lettering as specified in DIN 18 7
42、00; c) lettering as specified in DIN 30640 Part 2. Specifications relating to other suitable lettering styles are currently being prepared. 3.7 Illumination 3.7.1 External lighting External lighting is here understood to mean daylight or artificial room lighting. It is assumed that the light is suff
43、iciently bright to ensure that the scale can be read accurately. The following conditions are to be avoided: a) heavy shadow, glare and fluctuating illumination; b) reflections in the instrument glasses from light sources or from bright objects. 3.7.2 Integral lighting If scales are to be read in th
44、e dark (e.g. in vehicles), they shall be provided with integral lighting. DIN 43790 Page 5 Such lighting shall be provided by way of concealed edge lighting or by concealed vertical illumination of the scale. The reduced acuity of human vision in the dark may be partly compensated for by the followi
45、ng measures: a) provision of optimal contrast conditions (e.g. white scale against black background); b) the scale which appears as white against a black back- ground in daylight should preferably shine red in the dark. 3.8 Parallax Normally, scale and index (e.g. pointer), do not lie in the same pl
46、ane.This may lead to errors of observation due to parallax (angle of sight is not normal to the point of reading on the scale). These errors may be reduced or precluded by supplemen- tary design measures, e.g. a) designing pointer with bevelled tip (cf. DIN 16102 or DIN 16103); b) providing scale wi
47、th anti-parallax mirror (cf.DIN 16117); c) arranging for scale and pointer to lie in the same plane. 4 Calculation of scale geometry 4.1 Calculation of span As specified in subclauses 2.1.3 and 2.1.4, the measuring span or nominal span, m, is obtained as the difference between the maximum and minimu
48、m scale values. 4.2 Calculation of scale length Calculation of the minimum scale length on the basis of the following equation applies both for straight scales and for scales with a circular or part circular scale mark base: (9) t,in = amin . z where a is the scale spacing; z is the number of scale
49、divisions within the nominal range. Depending on the requirements of the application,?. is to be calculated from one of equations (10) to (13): m 2 =- (13) S (1 2) ntot 2=- n where n is the number of interpolated divisions within a scale division; ntot is the total number of interpolated divisionswithin the nominal range; m is the nominal or measuring span; s is the scale interval; vabs is the absolute resolution; v, is the relative resolution; Example 1: O 100 Note. Where a given relative resolution is prescribed (e.% urel =1,5%), it shall be checked whether the equa- tion m .
