Apparatus for controlling deformations of elongated object
SUBSTANCE: apparatus consists of a basic direction selector (BDS), sighting targets (ST), radiator control devices (RCD), a preprocessing unit (PPU) a unit interfacing device (UID) and a processing unit (PU), whose first inputs and outputs are connected to the RCD. The second output is connected to a display, the second, third and fourth inputs are connected to a keyboard, a temperature sensor and a reference temperature sensor mounted on the housing of the BDS, respectively. The fifth input of the PU is connected to a BDS amplifier through series connected PPU and UID, and the third input of the PU is connected through the UID to the second input of the PPU. The BDS includes series-arranged power supply and control unit (PCU), optical image coordinate receiver (OICR), which is in form of a matrix-type photosensitive charge-coupled device, the output of which is connected to an amplifier, a lens, which is optically interfaced through a prism block with sighting targets which are located at the controlled points of the object within the field of vision of the lens in corresponding optical channels formed by said prism block. Each sighting target is placed on the perimeter of the object, wherein the number of sighting targets is not less than the number of points determining the geometric shape of the object, and has a radiator connected to the first output of the corresponding RCD, and an air temperature sensor whose output is connected to the second input of the corresponding RCD. Special cases of the design of the apparatus are characterised by that, each radiator is in form of a semiconductor emitting diode; the processing unit, the keyboard and the display are merged into a unit which is in form of a portable computer; the lens, OICR, PCU and amplifier merged into a unit which is in form of a television camera.
EFFECT: providing the possibility of controlling the deformation profile of an elongated object, maximum angle of torque of the structure, as well as high accuracy of measurements while maintaining high speed of operation of the system.
4 cl, 1 dwg
The invention relates to a measuring and control technique, namely, devices for remote contactless control of the spatial position of the parts of the extended object optoelectronic methods, and can be used to control flatness, neveretheless, aperpendicular large extended structures in engineering, construction, aircraft and shipbuilding (e.g., tankers, icebreakers, docks, oil platforms, roofs of buildings and the like), the values of their deflection and angle of maximum twisting during operation.
A device for measuring deformations transport floating docks (A.S. 346573, MKI G01B 11/16, publ. 01.01.1972), which allows you to record the deformation of the dock with a length up to several hundred meters. It contains unit base areas containing consistently placed on the lens and prismatic block, forming two optical channel, and installed in each channel targets. And targets established in controlled points of the dock and the unit base direction between the controlled points.
Significant disadvantages of this device include the low accuracy of the measurements, due to the influence of the observation conditions and the subjectivity of visual measurements, the inability to control what iformatsii nose and hull individually and using prohibere as sensor alarms and automatic alignment of the dock. This is caused by the presence of prohibere only visual information about the deflection and the absence of electrical signals associated with the deformation values for controlled points.
Known optical programer, essential features which is the closest to the claimed invention and adopted for the prototype (U.S. Pat. Of the Russian Federation No. 2095755, from 06.06.95, IPC G01B 21/32, publ. 10.11.1997), which has the capacity to control deformation of the bow and stern separately, to use programer as sensor alarms and automatic alignment of the dock and register only the mechanical component of the deflection. The device includes sequentially arranged prismatic block and lens, designed for the education of the two optical channels, targets, placed at controlled points in the respective optical channels. In addition, the device comprises a series-connected coordinate the receiver of optical radiation (CPOE), mounted in front of the lens and the power amplifier, the programmable controller unit in the form of a keyboard, power supply and control coordinate receiver of optical radiation that is connected to the receiver, controls the emitter (CID), the input of each of which is connected to the programmable controller, and the output from sootvetstvujushej target goal made in the form of emitter display device and a temperature sensor are also connected to the programmable controller.
Significant disadvantages of this device include the fact that it is not possible to measure the profile deformation of the extended object, and record the maximum twisting angle of the surface, since the amount of information provided by placing only two target goals along the structure is insufficient to determine the magnitude of these deformations extended object.
Another disadvantage of the considered optical prohibere is the lack of possibilities to take into account the contribution of refraction of radiation in the final measurement result. Many years experience of carrying out measurements of optical methods shows that the refraction of the rays along the extended optical line can make a significant systematic error in the measurement result. The absolute value of the error made regular refraction, determined by the expression
where n is the refractive index of the propagation medium,
T1, T2the temperature at the beginning and the end of the track, respectively,
z is the length of the route.
The obstacles to achieve the desired technical result is the absence of the sensor is the information about the temperature at the endpoints of the optical channel between the target goal and the radiation receiver.
In addition, in this optical prohibere information from the photodetection parts in the computer, has redundancy, and because the control of large extended objects it is often necessary to distance from each other above-mentioned parts of the device, in this case the need arises to use the communication channels with high bandwidth, which can significantly increase the cost of embodiment of the device. This disadvantage can be eliminated by the implementation of distributed computing with application of the preprocessing unit, designed to reduce the redundancy of the video signal received in the processing unit and converting it to a form convenient for processing. In addition, this implementation of the calculations allows programmable controller to calculate the coordinates of a greater number of sighting targets without increasing the capacity of the latter with the speed of operation of the system.
The problem to which the invention is directed, is the ability to control the profile deformation of the extended object, the maximum twisting angle design, as well as increasing the measurement accuracy, while maintaining system performance.
This problem is solved due to the fact that the device for controlling the deformation the Nations of the extended object, containing unit basic directions, including connected to the power supply and control and mounted in front of the lens axis receiver optical radiation, optically coupled through a lens and prismatic block placed in controlled points of the object within the field of view of the lens in the respective optical channels formed this prismatic block, target goals, made in the form of emitters, each of which is connected to the first output of the control device of the emitter, the second output of each of which is connected to the first input of the processing unit and the first input of each of the control devices emitter is connected to the first output of the processing unit, to the second output of which is connected the indicator device, and the second and the third inputs of the processing unit connected to the keyboard and the temperature sensor, new, targets placed along the perimeter of the object, and the number of sighting targets is not less than the number of points defining the geometric shape of the object, with each sighting target further comprises an air temperature sensor, the output of which is connected to the second input of the corresponding control device emitter, to the fourth input of the processing unit connected to the sensor reference temperature, fixed to the body for which Attica basic directions, the latter contains an amplifier, an input connected to the output coordinate of the receiver of optical radiation, made in the form of a matrix of photosensitive charge-coupled device, and the output being the output of the unit base direction, is connected to the fifth input of the processing unit connected in series through the preprocessing unit and the interface unit blocks, and a third output of the processing unit is connected through the interface unit blocks with the second input of the preprocessing unit.
In addition, each of the emitters is made in the form of a semiconductor emitting diode. In addition, the processing unit, keyboard and display device are combined in a unit made in the form of a portable electronic computing machines. In addition, the lens axis receiver optical radiation, power supply and control and amplifier are combined in a unit made in the form of TV cameras.
The invention is illustrated in the drawing, which shows a block diagram of the device control deformation of extended objects. The device consists of a sighting goals 1, made in the form of radiators located around the perimeter of the measured object extended (the minimum number of sighting targets equal to the number of points that uniquely defines the geometric shape of the object), is troist management emitters 2, the base unit direction 3, the preprocessing unit 4, the device of the pair of blocks 5, the processing unit 6. The first inputs of each CID 2 is connected to the first output of the processing unit 6, and the second outputs of each CID 2 connected to the first input of the processing unit 6, the second output of which is connected an indicating device 7, to the second, third and fourth inputs of the processing unit 6 connected to the keyboard 8, the temperature sensor 9 and fixed to the body of the base unit direction 3 sensor reference temperature 10 respectively, the fifth input of the processing unit 6 is connected to the output of the amplifier 11 of the base unit direction 3 connected in series through the preprocessing unit 4 and the device blocks 5, and the third output processing unit 6 is connected through the interface unit 5 blocks to the second input of the preprocessing unit 4. Unit basic directions 3 contains consistently located prismatic unit 12 that generates optical channels, the lens 13, KOI 14 connected to the power supply and control KOI 15 and the amplifier 11, the output of which is connected to the input of the preprocessing unit 4, and the entrance to the exit KOI 14. Each target goal 1 is connected to the first output of the corresponding CID 2 emitter 16, optically coupled with the lens 13 through the prism block 12, and the air temperature sensor 1, connected to the input of the corresponding CID 2.
Device for controlling deformation of the extended object works as follows. Targets 1 are installed along the perimeter of the object (the minimum number of sighting targets equal to the number of points that uniquely defines the geometric shape of the object). Unit basic directions 3 is installed between them so that all the finer points were in the field of view of the lens 13. The command processing unit 6 each CID 2 produces sequential switching of the respective emitters 16, optical radiation which passes through the prism block 12, is sent to the lens 13, which generates a distribution of oblojennosti in the image plane. The received optical signal under the control of the power supply and control KOI 15 is converted coordinate the receiver of optical radiation 14 into an electrical signal passing through the amplifier 11, to the input of the preprocessing unit 4. The latter carries out the conversion signal to a digital mind and calculates the positions of the images of the emitters 16 in the coordinate system KOI 14. The calculated coordinates are sent to the input processing unit 6 through the interface unit 5 blocks. After you enable another emitter 16, simultaneously with the process of processing information about the state the targets 1, the processing unit 6 through the corresponding CID 2 requests data about the temperature in the optical channel. At this point, CID 2 polls the air temperature sensor 17, and sends the received data to the processing unit 6, and then to the other input of the latter receives information about the temperature from the sensor reference temperature 10 attached to the housing of the base unit direction 3. Next, in the processing unit 6 calculates the refractive component of the systematic error by the formula:
where n is the refractive index of the propagation medium;
T1T2- the temperature measured by the air temperature sensor 17, and the temperature measured by the sensor reference temperature 10, respectively;
zi- the distance from the sensor reference temperature to the i-th target goal 1;
and recalculation of the image coordinates of the source in space objects by the formula:
where hithe absolute deviation of the i-th controlled point;
- the vertical coordinate of the image of the i-th emitter on KPOI 14;
f' is the focal length of lens 13;
h0- the start position of the coordinate system.
The value of temperature of deformation is calculated by the processing unit 6 according to the data obtained from the temperature of the second sensor 9, installed in the environment of the location of the base structure according to the formula:
where ht- temperature deformation;
tPthe surface temperature of the controlled object;
tBthe substrate temperature of the controlled object, measured by temperature sensor 9;
k - coefficient of thermal deformation, defined by the structure;
and the size of the mechanical component of the deflection by the formula:
where- mechanical component of the deflection of the i-th controlled point;
hi- the total deflection of the i-th controlled point.
On detected values array deformationscontrolled points after approximation of the values of the deviations of the points situated on each side of the object, a polynomial of the fourth degree is the profile deformation. The values of the deformation of the points defining the geometry of an object at a known ratio of linear algebra is the angle of maximum twisting surface. Consider the example of determining the twisting angle of the floating dock. For this purpose, nose and stern designs must be installed on two targets. On the detected coordinates of the images of these target goals are calculated angular coefficients of the direct is, determining the tilt of the bow and stern relative to the horizon by the formula
where kH, kKthe angular coefficients of the direct determining the tilt of the bow and stern, respectively;
,,,vertical coordinates of the image target goals that are installed on the bow and stern, respectively;
,,,- horizontal coordinates of the image target goals that are installed on the bow and stern respectively.
The desired value, i.e. the angle of maximum twisting, is calculated by the following formula:
where φ is the angle of maximum twisting design of the dock.
Display device 7 displays the results, as the keyboard 8 is to set the operating modes of the device, the input threshold values of strain above which the processing unit 6 sends signals to activate the alarm and automatic alignment of the object.
An example of a specific implementation.
The emitters are made in the form of a semiconductor emitting diodes; air temperature sensors, the sensor reference temperature the tours and temperature sensor - in the form of temperature sensors; a control device of the emitter is made on the basis of microcontrollers the AVR family. Lens, coordinate the receiver of optical radiation, power supply and management, as well as the amplifier assembled in a single case and represent a television camera. Block preprocessing is performed on the basis of microcontroller with ARM architecture. Interface unit blocks are made in the form of the interface Converter. The processing unit 6 is made in the form of a portable electronic computing machine with a built-in keyboard and display device (block 6 is connected to the indicator device 8 and the keyboard 9 - see the drawing and description). Prismatic block is a structure of the unit prisms, consisting of pentaprism with roof and glued with her rectangular prism.
Thus, the claimed invention provides a device for controlling the deformation of the extended object, allowing you to control the profile of the deformation of the extended object and the maximum twisting angle of the surface, as well as to improve the accuracy of measurement while maintaining system performance.
1. Device for controlling deformation of the extended object containing unit basic directions, including connected to the power supply and control and mounted in front of the lens coordinate the th receiver of optical radiation, optically coupled through a lens and prismatic block placed in controlled points of the object within the field of view of the lens in the respective optical channels formed this prismatic block, target goals, made in the form of emitters, each of which is connected to the first output of the control device of the emitter, the second output of each of which is connected to the first input of the processing unit and the first input of each of the control devices emitter is connected to the first output of the processing unit, to the second output of which is connected an indicating device, and the second and the third inputs of the processing unit connected to the keyboard and the temperature sensor, wherein targets placed along the perimeter of the object, and the number of sighting targets is not less than the number of points defining the geometric shape of the object, with each sighting target further comprises an air temperature sensor, the output of which is connected to the second input of the corresponding control device emitter, to the fourth input of the processing unit connected to the sensor reference temperature, fixed to the body of the unit base direction, the latter contains an amplifier, an input connected to the output coordinate of the receiver of optical radiation, made in the form of a matrix is otechestvennoi of the charge-coupled device, and the output being the output of the unit base direction, is connected to the fifth input of the processing unit connected in series through the preprocessing unit and the interface unit blocks, and a third output of the processing unit is connected through the interface unit blocks with the second input of the preprocessing unit.
2. The device according to claim 1, characterized in that each of the emitters is made in the form of a semiconductor emitting diode.
3. The device according to claim 1, characterized in that the processing unit, keyboard and display device are combined in a unit made in the form of a portable electronic computing machine.
4. The device according to claim 1, characterized in that the lens axis receiver optical radiation, power supply and control and amplifier are combined in a unit, made in the form of a television camera.
SUBSTANCE: deformation detecting element with dispersion structures consists of piezoelectric plates on whose surface there is at least one interdigital converter and at least two dispersion reflecting structures, which uses the response lag time of the deformation detecting element as an information signal. The reflecting structures are on two sides of the interdigital transducers. The information signal can also be in form of the wave form or central frequency of a frequency-modulated probing signal, which ensures maximum amplitude response value of the deformation detecting element with dispersion structures.
EFFECT: higher accuracy of measuring deformation owing to use of information on the central frequency of the device.
2 cl, 1 dwg
FIELD: mechanical engineering; repair of vehicles.
SUBSTANCE: vehicle with damage body is lifted to preset height relative to floor, and check points on body are chosen. Part of points are arranged of sound part of body. Additional check point is marked on floor under bottom of body. Said point should be located at a distance from bottom not less than one fourth of maximum distance between chosen check points. Distances between all check points are measured, and basing on obtained data, three coordinates of all chosen check points are calculated by computer with determination of distribution of said check points in space. Then, by turning, check points of damage body are registered with similar check points in computer data base belonging to body of standard vehicle. Distribution of check points received in measurement is compared with distribution of check points in standard vehicle and, basing on results of measurement, value and direction of deformations of damaged body are determined.
EFFECT: simplified method at preservation of high accuracy of determination of deformations.
1 ex, 3 tbl, 2 dwg
FIELD: the invention refers to control of the state for example of textile materials at their interaction with working parts of technological equipment.
SUBSTANCE: the essence is in scanning the surface of the moving material with the aid of the sensitive element of a piezo-converter. The average value of the current linear sizes of the structural elements are calculated according to the number of the impulses generated by a piezo-converter and defined by the quantity of the elements of the structure (for example by the number of weave units) on the reference length of the part of the moving object. Periodically the received results are compared with the corresponding starting data of the structure of the rigid part of the material.
EFFECT: increases accuracy of the evaluation of the strain-deformed state of the moving easily deformed materials of a grid-type structure with simultaneous simplification of technical realization.
2 cl, 3 dwg
SUBSTANCE: polymer film with mechanoluminescence in the visible spectrum is deposited on the surface of an object via UV photopolymerisation. The film has high sensitivity to surface deformations and is transparent in the visible spectrum. Deformation and distribution of deformations on the surface of the object under analysis can be measured from the luminous intensity of the film.
EFFECT: high accuracy of control.
SUBSTANCE: method for study of cutter tool deformation in the process of cutting is as follows: one preliminarily applies crosswise close-pitched grooves on the blank surface while the lateral surface of the tool cutting end material is polished. Then one illuminates the polished lateral tool surface with a flux of coherent monochromatic radiation, forms an interference pattern and performs continuous registration of interference patterns changes. Then one implements the process of cutting in the modes concerned; determines power load deformation component by way of recalculation of differences between series of interference fringes having passed through varied cross-sections in interference patterns obtained in the process of cutting immediately before the crosswise groove and at the moment of the tool cutting edge being inside the groove.
EFFECT: performance of high-precision inertia-free contactless measurements of changes in the deformation field of the tool cutting edge material as a result of power loads under non-stationary cutting conditions, provision for an opportunity to calculate dynamics of the tool cutting edge strain and deformation condition and strength under such conditions.
2 cl, 3 dwg
SUBSTANCE: sensor includes two coaxially installed cylinders; external cylinder is made from strong material, for example metal, and internal cylinder with axial hole is made from optically sensitive material. Gap Δ between the above cylinders is filled with self-hardening bonding agent. Gap Δ, modulus of elasticity Eb of self-hardening bonding agent, d/D ratio (diameter d of axial hole of internal cylinder to its outer diameter D), thickness t of wall of external cylinder are determined as per the specified dependences.
EFFECT: improving measurement accuracy of high stress increases in mine rocks of improved strength owing to eliminating distortions of optic picture in photoelastic stress sensor.
SUBSTANCE: proposed device comprises system of specimen material clamps, loading and straining mechanism, measurement pickup made up of computer mouse rigidly coupled with coiled edge straightener pointer that may move across, along and about tested specimen, and recording unit. Recording unit comprises computer to convert straightener pointer travel into lengthwise and crosswise deformation, contraction ratio, conditional Poisson factor and allow visualising travel of said pointer on monitor and version results. Loading and straining mechanism is made up of spaced apart current conducting buses, one representing moving bus. Note here that said busses are connected with computer by aforesaid mouse.
EFFECT: higher accuracy and automatic measurements.
SUBSTANCE: optical fibre structure with Bragg lattices is put into composite material during production thereof. The spectral position of peaks of the Bragg lattices is measured after making the structure from the composite material and distribution of mechanical and thermal deformations inside the structure of the composite material is determined by solving the system of equations: , where f(T,ε) is the distribution function of mechanical and thermal deformations on the structure made from composite material (T is the temperature value, ε is the deformation value); f(Ex, y, z) is the distribution function of elastic properties of the structure made form composite material, Ex, y, z is the Young 's modulus tensor; f(αx, y, z, vx, y, z) is the distribution function of thermal characteristics of the composite material (αx, y, z is the coefficient of volume expansion tensor, vx, y, z is the thermal conductivity coefficient tensor);f(Fload, FT) is the distribution of mechanical and temperature effects on the structure made from composite material (Fload is the value of the mechanical effect, FT is the value of the temperature effect); fFBG(T,ε) is the function of total deformation on the path of the optical fibre with Bragg lattices (T is the temperature value, ε is the deformation value); fi-FBG(Δλ) is shift transformation function of the position of the i-th peak of the Bragg lattice to the temperature value and deformation (Δλ is the displacement of the peak of the Bragg lattice). The optical fibre contains two or more Bragg lattices which are not more than 5 mm long. The distance between the Bragg lattices and one optical fibre is not less than 5 mm.
EFFECT: high measurement accuracy.
3 cl, 15 dwg
SUBSTANCE: proposed transducer comprises load secured on controlled element and strain-gage transducer to convert voltage across stress-optical element into electric signal, and signal processing unit. Load is made up of plate to concentrate strain at stress-optical element. Stress-optical element is fixed in said plate as-stressed so that initial stress force acts in two mutually perpendicular directions. Note that stress-optical element is fixed at plate thinned center by means of Morse taper. Note also that, additionally, two mutually perpendicular through cuts are made not corrupting plate integrity, cuts axes being directed at 45° to loads axis. Cuts axes are aligned with that of taper hole for stress-optical element attachment.
EFFECT: higher sensitivity, thermal compensation.
5 cl, 1 dwg
SUBSTANCE: coating composition contains resorcinol-formaldehyde resin SF-282 with addition of a carbamidoformaldehyde concentrate KFK-85, and a liquid hardener of carbamide-formaldehyde concentrate - aqueous formalin solution, ethylene glycol and starch OZ-102, where components are taken in the following ratio per 100 pts. wt of the resorcinol-formaldehyde, in %: carbamide-formaldehyde concentrate KFK-85 35-50; hardener 22-25.
EFFECT: coating has short hardening time, high resistance to hydrocarbon media.
1 tbl, 4 ex
SUBSTANCE: holographic interferometre has a radiation source with a collimator, an objective lens, an object under analysis, a photoplate and an intermediate optical medium placed between the photoplate and the object under analysis. The intermediate optical medium is in form of a periodic structure of projections and depressions, which can be made with period of 200-5000 mcm and ratio of the side of the projection to distance between the projections equal to 1:10.
EFFECT: higher accuracy of measuring deformations of the flat surface of solid-state electronics elements.
3 cl, 11 dwg
SUBSTANCE: surface is illuminated with coherent light, digitised and the sequence of its video images is stored. A sample of N readings is formed for each point of the digitised image, containing the time variation of the illumination level and dispersion and mathematical expectation are then calculated for each sample, the ratio of which is then used to image the localisation zones of the surface deformation.
EFFECT: more accurate imaging of deformation localisation zones owing to use of high-resolution video cameras; higher information content of real-time imaging deformation zones and establishment of a direct relationship between measured values and values of rate of deformation in the analysed region.
FIELD: power industry.
SUBSTANCE: device includes in-series installed stations: of integrity check of items, two stations for dividing the items into two streams, control station of side surface and control station of ends surface of items, which are installed in each stream, as well as integrating station of streams of items. Integrity check station of items contains CCD chamber. Each station for dividing and integrating the streams contains optical sensor and stop for shaping and cutting off the post of items of the specified length. Control station of side surface contains rotating rolls, lighting device of controlled items and CCD ruler. Control station of end surfaces includes rotor divided with a groove into two parts in each of which there are slots for arrangement of items, two CCD chambers with built-in radiator to control the items. All the control stations are equipped with blowing devices of defective items as well.
EFFECT: automated, operational, high-reliable control of cylindrical objects for availability and character of surface defects, high efficiency of process operation of the control.
6 cl, 8 dwg
FIELD: the invention refers to checking devices.
SUBSTANCE: the arrangement for checking misalignment has a source of light, two optoelectronics systems each with flexible illuminating and receiving beams of light guides located coaxially and photoreceivers registering signals in one plane. The arrangement has two additional optoelectronics systems and registers signals from the source of lighting in two cross-perpendicular planes together with the first two optoelectronics systems. At that the outputs of receiving light guides are optically compatible with photodiode matrixes with the outputs of matrixes connected with the inputs of the unit of analogue-digital conversion and the outputs of the unit of analogue-digital conversion are connected with the inputs of the computing unit.
EFFECT: the invention simplifies the construction and increases accuracy and productivity of checking operations.
FIELD: optical engineering.
SUBSTANCE: flat object is illuminated with coherent radiation to measure movement at the plane and angle of inclination of flat part of surface. Radiation dissipated by object is directed to optical system, which carries out integral optical transformation of wave field. Two inverse Fourier-Frenel transforms are used on the base of collecting lens. Intermediate and final results are fixed onto photographic plates, which form specklegram and interferogram. Object and photographic plate are disposed at different varying distances from lens. Values to be measured are divided and required sensitivities of measurement are found, which depend on focal length f of first lens, parameters of first optical inverse Fourier-Frenel transform φ, δ and on focal length f second lens and parameter α of second optical inverse Fourier-Frenel transform.
EFFECT: varying sensitivity; widened range of measurement of shift and inclination.
FIELD: measurement technology.
SUBSTANCE: holographic unit for Measuring Value of stress-deformed condition of object has base, coherent radiation source, aids for representing interference pattern onto surface of object, radiation receiver and unit for setting stress-deformed condition which also has drilling unit. Unit for setting stress-deformed condition is provided with post which embraces base and has detachable joint with the base. The unit also has bore rod provided with clamp. Post is made to have object being fixed onto its surface and is provided with bushing having round jig hole. The hole is made in such a manner that its axis crosses axes of incident and reflected beams at the same point. Bore rod conjugates with post through round jig hole. Repeated measurements are excluded due to reduction in mechanical influence onto base of device and members of its optical system during drilling material of object and operation of mechanical gate.
EFFECT: improved precision of measurement.
6 cl, 5 dwg