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The fibre optic sensor in the in-process measurement of surface roughness
The fibre optic sensor in the in-process measurement of surface roughness Z. Dinghai, L. Haibao and Y. S h e n g h u a
Department of Precision Instrument Engineering, Tianjin University, Tianjin, P.R. China In the paper, a NFF type fibre optic displacement sensor is proposed, which now has been adopted to measure surface roughness. The system with this sensor is designed to be suitable for in-process measurement, in which a Z8 single-chip microcomputer is matched. The whole system is supported by assembly programs and is automatic, intelligent and flexible. The output changes of the sensor are discussed respectively for several special cases, and some necessary measures are described for the real operational environments. Keywords: Fibre optic sensor, in-process measurement, surface roughness
1. Introduction In future machining and manufacturing, quality evalution is a necessary part for a factory. Detecting or dimensional control has taken a decisive role in directing and examining the machining ability. The in-process measurement of surface roughness of workpieces is one of the main difficulties. Many methods have been proposed by some researchers in several previous papers (Wolf et al, 1983; Almarzouk, 1983; Ruffing, 1986). The traditional method - a contact method with a needle s e n s o r - has been thought the most reliable. But in practical applications there are some problems, as follows. First, it is a contact measurement and the measured surface may be touched and spoiled. Second, the measurement resolution is limited to the diameter size of the top of the needle. Finally, the measuring range is not wide and the efficiency is low. It is clear that the system by this method cannot be exploited for inprocess measurement. Church (1983) has done research on the comparison of optical and mechanical measurement for a precision-machined surface. The results show that the two methods are identical to each other after appropriate processing. Our work deals with the development of a non-contact sensor for possible use in on-line measurement. The purpose of the sensor is to enable our system to obtain the parameters of surface. One method often invoked to accomplish the task is a direct optics method, which can be used to measure the fine shape of rough surface, and includes light-spot displacement, interferometer, focusing and critical angle of complete reflection, etc. The main difficulty encountered here, however, is the finprocess" problem; it does not operate well in adverse environments. One can alleviate this problem to a great extent by another method, the indirect optics method, in which the statistical parameters of the measured surface can be acquired. It includes light scattering, speckle pattern, etc. The speckle pattern method is based on the fact that the light is scattered and a speckle pattern is produced in the spatial field when the 'rough' surface is radiated by coherent light, and the root-mean-square
172
value of the fine shape radiated can be seen by the photoelectric device. The light scattering method is in the base of the electromagnetic wave scattering theory developed by Beckmann and Spizzichino (1963), in which the rough surface is proposed as a smooth Gaussian random process. The results deduced show that the scattered power is related to the root-mean-square and correlation length of the surface. We have chosen the light scattering method to fit a system with simple configuration and low cost. In the following sections we will discuss respectively the principle of the sensor, the system configuration, the experimental results and summary.
2. O p e r a t i o n a l principle of the s e n s o r Fig l shows the configurations of the sensor. The optic fibres are divided into two parts: the internal circle filled with incident fibres and the external circular ring with receiving fibres. The distribution of fibres is uniform in each area. In Fig 1, the surface is specular so that the model can be analysed by a geometrical method. Assume that the diameter of the internal fibre-bundle is D l, that of the external fibre-bundle is D2, and the distance from the bundle end to the surface is d. Presume that angled incident light is coupled into the incident bundle without loss and scattering, and that the thickness of its wrapper is neglected. When the incident angle is ~b (less than the critical angle 0c), according to geometric relation, we have x = 2,
d,
...(1)
tgch
q =x+Dl/2
...(2)
and use two factors k and m defined as m = 2 * q/D1
. . . (3)
k = DZ/D1
. . . (4)
In the case of the sensor used here, k = 3, and the
Measurement Vol 9 No 4, Oct-Dec 1991
Dinghai, Haibao and Shenghua efficient area receiving the reflected p o w e r is Sa = ~'* ( m - l )
* 0 n + l ) * D1/4
Sa = ~ * ( r e + l ) * ( 5 - m ) * D1/4
1.7.
m <~ 3
3 < m <~ 5 . . . (5)
Consider the angular incidence and suppose all the ray is meridian and is distributed uniformly within the incident fibres. The relation between the irradiance Ir obtained by the receiving fibres and Io at the end of the incident fibres is h" = p • 1o * ( 5 - m ) / 4 * ( r e + l )
m ~< 3
Ir = p • 1o/4 * ( m - l )
m > 3
. . . (6)
where p is the coefficiency relative to the loss of fibres and the albedo of surface. T h e r e f o r e , the light p o w e r in the receiving fibres can be d e d u c e d . . . (7)
P = Ir • Sa
1.11
I
.8 .6
.,! .?.. o0
i
!
I
2.0
3.0
4.0
-
1.0
m
Fig 2 Diagrams o f Sa, Ir, and P in angular incidence
If we replace Ir and Sa by Eqns (5) and (6) respectively, the following equation can be derived as P = Po * ( m - l )
* (5-m)
m ~< 3
P = Po * ( m + l )
* (5-m)/(rn-1)
3 < rn <- 5 ...
(8)
where Po = P • rr • D1 • lo/16. Fig 2 shows the results
of Eqn (8) calculated and normalised by c o m p u t e r . In the case of uni-angular incidence 4~ which is distributed uniformly from 0 to Oc, when the angle 4~ varies a mini-angle dO, the c o r r e s p o n d i n g changes of q and Sa are given by dq = (2 • x/(sin 4~ * cos 4~)) d~b . . . (9)
dSa = 2 • ~ • ( x + D l / 2 ) dq
and Sa = I dSa
•
(10)
o
3
41
replacing dSa by E q n (9) Sa = 1 6 , 7 r . (tgOc* d ) 2 + 4 .
7 r . D1 * tgOc* d , . . (11)
d <~ doc
W h e n d = D I / 2 . tgOc, Sa reaches the m a x i m u m value equivalent to 6 • 7r • D12, thus Sa = 1 6 , ~ r . (tgOc* d ) 2 + 4 .
7 r . D1 * tgOc* d
d <~ doc Sa = 6 * rr • D12
. . . (12)
d > doc
Sa. Ir and P curves normalised are shown in Fig 3. The practical characteristic curve P will change in the declining segment c o r r e s p o n d i n g to the different incident
1.2
1.0
Sa
\It
.8 .6 "
-
dog
.4 .Z
0.0 Fig 1 Sensor structure and model. (top) View o f bottom," (lower) geometric analysis Measurement Vol 9 No 4, Oct-Dec 1991
Z
I
|
!
l.O
2.0
3.0
4.0
!
5.0 nt
Fig _7 Diagrams o f Sa, h', and P in uni-angular incidence 173
Dinghai, Haibao and Shenghua matched, including the A/D converter, interface and expanded board, and Z8 system board. In Fig 5 the additional reference fibre-bundle is exploited to eliminate the intensity fluctuation of the laser source. The beam splitter separates the light from a He-Ne laser into two parts: one is coupled into the incident bundle and another into the referent bundle. The intensity modulator converts the constant intensity into an alternative signal with a central f r e q u e n c y f = 3.75 kHz. Its purpose is to remove the effect of the ambient lighting on the measurement results. Two photocells receive the power from the output ends of the incident bundle and reference bundle. The sensor is equipped on a guide, which is driven by a 3-phase step motor. We have set up the experimental system mentioned above in our laboratory. From driving the step motor and changing the distance d between the sensor and the workpiece, we can obtain the characteristic curve P dependent on d. The experimental results show that the variation at the crest value point (d = doc) gets most obvious when the surface roughness varies. Fig 6 gives the results of five rough samples (plane) machined by grinding. In addition, we get the relational curve between the crest value Pm and the corresponding contour average value Ra from a set of parts (cylindric). The diameter of the part is about 43 ram. The curve is illustrated in Fig 7. With the help of this curve, we therefore
1.2
1.0 .8
.8 d .4
,,
C
.2, 0.0 0.0
1.0
2.0
3.0
4.0
5.0 6.0
d
Fig 4 Comparison of the characteristic P-diagrams in different incidence: (a) angular; (b) uni-angular; (c) quasi-isotropic; (d) isotropic
cases, which includes angular, uni-angular, isotropic and quasi-isotropic incidence. Their differences are illustrated in Fig 4. In general, the common expression of P can be expressed as follows
P = ~(o',T) • K(d) * Io
. . . (13)
1.Z
where 13(or, T) expresses the total coefficiency dealing with the loss of fibre, the root-mean-square o-and correlation length T of real surface. The interesting characteristic curve P always reaches the maximum value Pm at certain point d = doc, and the magnitude of the crest value only depends on o- and T of the surface when d is constant in terms of the scattering theory (Beckmann and Spizzichino, 1963) and Eqn (13). The statistic parameters from the crest value can therefore be derived.
P I
1.0 .8 .6 .4
.Z 3. S y s t e m c o n s i d e r a t i o n s resu Its
and experimental
0.0
,
,
i
!
i
i
do<.
The system configuration with a fibre optic sensor is demonstrated in Fig 5. In order to control and calculate, the Z8 microcomputer system of Zilog Corporation is
0.0 I.O ?...0 3.0
d
4.0 5.0 6.0 7.0
Fig 6 P-curves of five rough samples (plane)
3
8
~
11--
i3
7
I
5 !5
174
Fig 5 System configuration: (1) laser; (2) modulator; (3) beam splitter; (4) incident fibre-bundle; (5) sensor head; (6) measured surface; (7) referent fbre-bundle; (8) receiving fibre-bundle; (9) guide; (10) step motor; (11) photocells; (12) amplifier; (13) A/D converter; (14) interface and expanded board; (15) Z8 system board; (16) driving system Measurement Vol 9 No 4, Oct-Dec 1991
Dinghai, Haibao and Shenghua 4. Discussion and conclusion
PI
1130
150 140 130
II0
0.0
0.2
0.4
0.6
0.8
1.0~
We have described some important operational considerations and experimental results required to utilise a NFF type fibre optic sensor in measuring the surface roughness. So far, our efforts have concentrated on the mathematical models and several measures taken for ambient lighting, fluctuation of light source and so on. Beside, it must be noted that the different machine methods and machined materials have some effects on the albedo of the surface. Further work, therefore, should be done in the future to make the system more suitable for operation in-process. With the further sorting of the shape features of the surfaces and the accumulation of data, the system will be adopted more commonly.
Fig 7 The relational diagrams of Pm and Ra for 10 cylindrical parts
5. References
can derive the Ra from the Pm measured by the said system. In the whole system the 2K assembly programs harmonise efficiently its control and processing. We have acquired a system repeatability superior to 0.3%, a measurement stability superior to 0.1% in a static tracing doc for plane samples, the measurement range of Ra from 0.08 to 0.90 p,m for cylindrical parts. These results are relatively satisfactory.
Almarzouk, K. 1983. "Three-beam interferometric profilometer', Appl Opt,22 (12). Beckmann, P., and Spizzichine, A. 1963. The scattering of electromagnetic waves from rough surface. Pergamon Press Ltd, New York. Church, E. L. 1983. 'Direct comparison of mechanical and optical measurement of the finish of precisionmachined surface'. Proc of SPIE, 429. Ruffing, B. 1986. 'Application of speckle-correlation methods to surface roughness measurement'. J Opt Soc Am A, 3(8). Woff, W. L. etal, 1983. "Scatter measurements on LAK9 and SF1 glasses at 0.91 p,m', Proc of SPIE, 429.
Slovak Metrological Society The Slovak Metrological Society (SMS) was established last year in D T 2:ilina, to help in developing metrology and measurement in Slovakia. The director and coordinator of the society is the Czechoslovak Metrological Institute (QSMI~I) - the centre of Czechoslovak metrology. Together with the Federal Weights and Measures Office (FUNM), State metrological centres, centres of calibration service and production plant metrological centres, it co-ordinates the main areas of present metrology in the (~SFR. The proceedings of the opening congress began with a paper by Dr- Ing Weidlich on the aims and tasks of the SMS. Next were papers entitled 'Future arrangement of the Czechoslovak Metrology and Calibration Service', 'Legal adjustment of metrology after 1990 and its impact upon users organisations', 'Metrology - a tool for proving conditions of permanent securing of production and service quality'. These papers were read by Ing Brezina director of CSMU and member of the commission I M E K O TC-14 and others.
MeasurementVol 9 No 4, Oct-Dec 1991
The main attention was paid to: cooperation with organisations of WECC, E U R O M E T , C E N / C E N E L E C , or others, as well as how to participate on activities in the framework of ISO, ISO/IEC; the unfinished state of the law "On Metrology (parts I - VI)'; choice of models securing quality; problems of educating metrologists in (~SFR, etc. The presented papers together with the list of participants of the congress are given in the proceedings: "Foundation Congress of the Slovak Metrological Society, D T Zilina, 1990.' The congress approved rules for the SMS and a program of activity for three years. The principles of management and undertaking were approved and a committee of 15 members with Dr- Ing Weidlich at its head, and a control board with three members, have been elected. Those interested in membership, cooperation or sponsorship activity are asked to write to Assoc Prof Josef Mandak, SMS, Tr. L. Novomesk6ho IV/487,842 55 Bratislava, (~SFR.
175
Department of Precision Instrument Engineering, Tianjin University, Tianjin, P.R. China In the paper, a NFF type fibre optic displacement sensor is proposed, which now has been adopted to measure surface roughness. The system with this sensor is designed to be suitable for in-process measurement, in which a Z8 single-chip microcomputer is matched. The whole system is supported by assembly programs and is automatic, intelligent and flexible. The output changes of the sensor are discussed respectively for several special cases, and some necessary measures are described for the real operational environments. Keywords: Fibre optic sensor, in-process measurement, surface roughness
1. Introduction In future machining and manufacturing, quality evalution is a necessary part for a factory. Detecting or dimensional control has taken a decisive role in directing and examining the machining ability. The in-process measurement of surface roughness of workpieces is one of the main difficulties. Many methods have been proposed by some researchers in several previous papers (Wolf et al, 1983; Almarzouk, 1983; Ruffing, 1986). The traditional method - a contact method with a needle s e n s o r - has been thought the most reliable. But in practical applications there are some problems, as follows. First, it is a contact measurement and the measured surface may be touched and spoiled. Second, the measurement resolution is limited to the diameter size of the top of the needle. Finally, the measuring range is not wide and the efficiency is low. It is clear that the system by this method cannot be exploited for inprocess measurement. Church (1983) has done research on the comparison of optical and mechanical measurement for a precision-machined surface. The results show that the two methods are identical to each other after appropriate processing. Our work deals with the development of a non-contact sensor for possible use in on-line measurement. The purpose of the sensor is to enable our system to obtain the parameters of surface. One method often invoked to accomplish the task is a direct optics method, which can be used to measure the fine shape of rough surface, and includes light-spot displacement, interferometer, focusing and critical angle of complete reflection, etc. The main difficulty encountered here, however, is the finprocess" problem; it does not operate well in adverse environments. One can alleviate this problem to a great extent by another method, the indirect optics method, in which the statistical parameters of the measured surface can be acquired. It includes light scattering, speckle pattern, etc. The speckle pattern method is based on the fact that the light is scattered and a speckle pattern is produced in the spatial field when the 'rough' surface is radiated by coherent light, and the root-mean-square
172
value of the fine shape radiated can be seen by the photoelectric device. The light scattering method is in the base of the electromagnetic wave scattering theory developed by Beckmann and Spizzichino (1963), in which the rough surface is proposed as a smooth Gaussian random process. The results deduced show that the scattered power is related to the root-mean-square and correlation length of the surface. We have chosen the light scattering method to fit a system with simple configuration and low cost. In the following sections we will discuss respectively the principle of the sensor, the system configuration, the experimental results and summary.
2. O p e r a t i o n a l principle of the s e n s o r Fig l shows the configurations of the sensor. The optic fibres are divided into two parts: the internal circle filled with incident fibres and the external circular ring with receiving fibres. The distribution of fibres is uniform in each area. In Fig 1, the surface is specular so that the model can be analysed by a geometrical method. Assume that the diameter of the internal fibre-bundle is D l, that of the external fibre-bundle is D2, and the distance from the bundle end to the surface is d. Presume that angled incident light is coupled into the incident bundle without loss and scattering, and that the thickness of its wrapper is neglected. When the incident angle is ~b (less than the critical angle 0c), according to geometric relation, we have x = 2,
d,
...(1)
tgch
q =x+Dl/2
...(2)
and use two factors k and m defined as m = 2 * q/D1
. . . (3)
k = DZ/D1
. . . (4)
In the case of the sensor used here, k = 3, and the
Measurement Vol 9 No 4, Oct-Dec 1991
Dinghai, Haibao and Shenghua efficient area receiving the reflected p o w e r is Sa = ~'* ( m - l )
* 0 n + l ) * D1/4
Sa = ~ * ( r e + l ) * ( 5 - m ) * D1/4
1.7.
m <~ 3
3 < m <~ 5 . . . (5)
Consider the angular incidence and suppose all the ray is meridian and is distributed uniformly within the incident fibres. The relation between the irradiance Ir obtained by the receiving fibres and Io at the end of the incident fibres is h" = p • 1o * ( 5 - m ) / 4 * ( r e + l )
m ~< 3
Ir = p • 1o/4 * ( m - l )
m > 3
. . . (6)
where p is the coefficiency relative to the loss of fibres and the albedo of surface. T h e r e f o r e , the light p o w e r in the receiving fibres can be d e d u c e d . . . (7)
P = Ir • Sa
1.11
I
.8 .6
.,! .?.. o0
i
!
I
2.0
3.0
4.0
-
1.0
m
Fig 2 Diagrams o f Sa, Ir, and P in angular incidence
If we replace Ir and Sa by Eqns (5) and (6) respectively, the following equation can be derived as P = Po * ( m - l )
* (5-m)
m ~< 3
P = Po * ( m + l )
* (5-m)/(rn-1)
3 < rn <- 5 ...
(8)
where Po = P • rr • D1 • lo/16. Fig 2 shows the results
of Eqn (8) calculated and normalised by c o m p u t e r . In the case of uni-angular incidence 4~ which is distributed uniformly from 0 to Oc, when the angle 4~ varies a mini-angle dO, the c o r r e s p o n d i n g changes of q and Sa are given by dq = (2 • x/(sin 4~ * cos 4~)) d~b . . . (9)
dSa = 2 • ~ • ( x + D l / 2 ) dq
and Sa = I dSa
•
(10)
o
3
41
replacing dSa by E q n (9) Sa = 1 6 , 7 r . (tgOc* d ) 2 + 4 .
7 r . D1 * tgOc* d , . . (11)
d <~ doc
W h e n d = D I / 2 . tgOc, Sa reaches the m a x i m u m value equivalent to 6 • 7r • D12, thus Sa = 1 6 , ~ r . (tgOc* d ) 2 + 4 .
7 r . D1 * tgOc* d
d <~ doc Sa = 6 * rr • D12
. . . (12)
d > doc
Sa. Ir and P curves normalised are shown in Fig 3. The practical characteristic curve P will change in the declining segment c o r r e s p o n d i n g to the different incident
1.2
1.0
Sa
\It
.8 .6 "
-
dog
.4 .Z
0.0 Fig 1 Sensor structure and model. (top) View o f bottom," (lower) geometric analysis Measurement Vol 9 No 4, Oct-Dec 1991
Z
I
|
!
l.O
2.0
3.0
4.0
!
5.0 nt
Fig _7 Diagrams o f Sa, h', and P in uni-angular incidence 173
Dinghai, Haibao and Shenghua matched, including the A/D converter, interface and expanded board, and Z8 system board. In Fig 5 the additional reference fibre-bundle is exploited to eliminate the intensity fluctuation of the laser source. The beam splitter separates the light from a He-Ne laser into two parts: one is coupled into the incident bundle and another into the referent bundle. The intensity modulator converts the constant intensity into an alternative signal with a central f r e q u e n c y f = 3.75 kHz. Its purpose is to remove the effect of the ambient lighting on the measurement results. Two photocells receive the power from the output ends of the incident bundle and reference bundle. The sensor is equipped on a guide, which is driven by a 3-phase step motor. We have set up the experimental system mentioned above in our laboratory. From driving the step motor and changing the distance d between the sensor and the workpiece, we can obtain the characteristic curve P dependent on d. The experimental results show that the variation at the crest value point (d = doc) gets most obvious when the surface roughness varies. Fig 6 gives the results of five rough samples (plane) machined by grinding. In addition, we get the relational curve between the crest value Pm and the corresponding contour average value Ra from a set of parts (cylindric). The diameter of the part is about 43 ram. The curve is illustrated in Fig 7. With the help of this curve, we therefore
1.2
1.0 .8
.8 d .4
,,
C
.2, 0.0 0.0
1.0
2.0
3.0
4.0
5.0 6.0
d
Fig 4 Comparison of the characteristic P-diagrams in different incidence: (a) angular; (b) uni-angular; (c) quasi-isotropic; (d) isotropic
cases, which includes angular, uni-angular, isotropic and quasi-isotropic incidence. Their differences are illustrated in Fig 4. In general, the common expression of P can be expressed as follows
P = ~(o',T) • K(d) * Io
. . . (13)
1.Z
where 13(or, T) expresses the total coefficiency dealing with the loss of fibre, the root-mean-square o-and correlation length T of real surface. The interesting characteristic curve P always reaches the maximum value Pm at certain point d = doc, and the magnitude of the crest value only depends on o- and T of the surface when d is constant in terms of the scattering theory (Beckmann and Spizzichino, 1963) and Eqn (13). The statistic parameters from the crest value can therefore be derived.
P I
1.0 .8 .6 .4
.Z 3. S y s t e m c o n s i d e r a t i o n s resu Its
and experimental
0.0
,
,
i
!
i
i
do<.
The system configuration with a fibre optic sensor is demonstrated in Fig 5. In order to control and calculate, the Z8 microcomputer system of Zilog Corporation is
0.0 I.O ?...0 3.0
d
4.0 5.0 6.0 7.0
Fig 6 P-curves of five rough samples (plane)
3
8
~
11--
i3
7
I
5 !5
174
Fig 5 System configuration: (1) laser; (2) modulator; (3) beam splitter; (4) incident fibre-bundle; (5) sensor head; (6) measured surface; (7) referent fbre-bundle; (8) receiving fibre-bundle; (9) guide; (10) step motor; (11) photocells; (12) amplifier; (13) A/D converter; (14) interface and expanded board; (15) Z8 system board; (16) driving system Measurement Vol 9 No 4, Oct-Dec 1991
Dinghai, Haibao and Shenghua 4. Discussion and conclusion
PI
1130
150 140 130
II0
0.0
0.2
0.4
0.6
0.8
1.0~
We have described some important operational considerations and experimental results required to utilise a NFF type fibre optic sensor in measuring the surface roughness. So far, our efforts have concentrated on the mathematical models and several measures taken for ambient lighting, fluctuation of light source and so on. Beside, it must be noted that the different machine methods and machined materials have some effects on the albedo of the surface. Further work, therefore, should be done in the future to make the system more suitable for operation in-process. With the further sorting of the shape features of the surfaces and the accumulation of data, the system will be adopted more commonly.
Fig 7 The relational diagrams of Pm and Ra for 10 cylindrical parts
5. References
can derive the Ra from the Pm measured by the said system. In the whole system the 2K assembly programs harmonise efficiently its control and processing. We have acquired a system repeatability superior to 0.3%, a measurement stability superior to 0.1% in a static tracing doc for plane samples, the measurement range of Ra from 0.08 to 0.90 p,m for cylindrical parts. These results are relatively satisfactory.
Almarzouk, K. 1983. "Three-beam interferometric profilometer', Appl Opt,22 (12). Beckmann, P., and Spizzichine, A. 1963. The scattering of electromagnetic waves from rough surface. Pergamon Press Ltd, New York. Church, E. L. 1983. 'Direct comparison of mechanical and optical measurement of the finish of precisionmachined surface'. Proc of SPIE, 429. Ruffing, B. 1986. 'Application of speckle-correlation methods to surface roughness measurement'. J Opt Soc Am A, 3(8). Woff, W. L. etal, 1983. "Scatter measurements on LAK9 and SF1 glasses at 0.91 p,m', Proc of SPIE, 429.
Slovak Metrological Society The Slovak Metrological Society (SMS) was established last year in D T 2:ilina, to help in developing metrology and measurement in Slovakia. The director and coordinator of the society is the Czechoslovak Metrological Institute (QSMI~I) - the centre of Czechoslovak metrology. Together with the Federal Weights and Measures Office (FUNM), State metrological centres, centres of calibration service and production plant metrological centres, it co-ordinates the main areas of present metrology in the (~SFR. The proceedings of the opening congress began with a paper by Dr- Ing Weidlich on the aims and tasks of the SMS. Next were papers entitled 'Future arrangement of the Czechoslovak Metrology and Calibration Service', 'Legal adjustment of metrology after 1990 and its impact upon users organisations', 'Metrology - a tool for proving conditions of permanent securing of production and service quality'. These papers were read by Ing Brezina director of CSMU and member of the commission I M E K O TC-14 and others.
MeasurementVol 9 No 4, Oct-Dec 1991
The main attention was paid to: cooperation with organisations of WECC, E U R O M E T , C E N / C E N E L E C , or others, as well as how to participate on activities in the framework of ISO, ISO/IEC; the unfinished state of the law "On Metrology (parts I - VI)'; choice of models securing quality; problems of educating metrologists in (~SFR, etc. The presented papers together with the list of participants of the congress are given in the proceedings: "Foundation Congress of the Slovak Metrological Society, D T Zilina, 1990.' The congress approved rules for the SMS and a program of activity for three years. The principles of management and undertaking were approved and a committee of 15 members with Dr- Ing Weidlich at its head, and a control board with three members, have been elected. Those interested in membership, cooperation or sponsorship activity are asked to write to Assoc Prof Josef Mandak, SMS, Tr. L. Novomesk6ho IV/487,842 55 Bratislava, (~SFR.
175