WMT 5 - Module on Tensometric Cells EN V-101 301104 · active Wheatstone bridge. Main metrological characteristics of load cells of the RTN type are Main metrological characteristics

USER’S RESOURCES BOOK

WEIGHING ACADEMY

Tensiometric Cells

Version 1.01 September 2004

Kadlec, spol. s r.o. Veleslavínova 19 746 01 Opava

This project has been funded with the support of the European Community. The content of this project does not necessarily reflect the position of the European Community

or the National Agency, nor does it involve any responsibility on their part.

(c) 2004 All rights reserved

Weighing Academy Tensiometric Cells

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Content

Content........................................................................................................................... 2 5. Basic element of a scale – tensiometric cell ................................................................. 3 5.1 Principle of a cell with metal tensiometers............................................................. 3 5.2 Practical example of a cell with parameters of SCHENCK RTN type ......................... 5 5.3 Cells – division by output measuring signals.......................................................... 8 5.4 Internal structure of a tensiometric cell................................................................. 9 5.4.1 Examples of various types of tensiometers of HBM producer...........................10 5.5 Correct use of tensiometric cells in practise..........................................................11 5.5.1. Principles for correct installation of cells.........................................................18 5.5.2 Principles for correct installation of cells – principles summary .......................22 5.6. Individual types of cells / practical examples /......................................................23 5.6.1 Single point – cell for eccentric loads type Revere 652....................................23 5.6.2 Single ended bending beam REVERE HCB......................................................27 5.6.3 Double ended bending beam REVERE 5103 ...................................................30 5.6.4 Compression cell REVERE CSP-M..................................................................32 5.6.5 Universal cell „ S“ for tension and pressure REVERE 9363...............................34 5.7 Digital tensiometric cell – principle.......................................................................36 5.7.1 Digital cell HBM FIT for dynamic weighing .....................................................36 5.8 Other types of cells for measuring force and weighing bodies ...............................39 5.8.1 Semiconductor tension cells Microcell and L-Cell.............................................39 5.9. Test...................................................................................................................41


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5. Basic element of a scale – tensiometric cell

5.1 Principle of a cell with metal tensiometers

Basic element of a scale, thus an element which converts inflicting force on weight carrier is a cell. This element enabled construction of modern scale with high speed and accuracy measurement. Most widespread type for use in electronic scales is a tensiometric cell with metal tensiometers.

Load cell Measured mass in load cells is transformed into a electric signal. Its metrological characteristics significantly affect accuracy of all types of electromechanical scales. According to IOLM, ( International Organisation of Legal Metrology) directive IR60, load cells are divided into accuracy classes A, B, C, D. For industrial weighing technology are actual load cells of C class, whose measuring principle is almost solely based on application of metal tensiometers. Accuracy class of a load cell is determined by maximum number n of verification intervals e, representing the number of numerical steps in which the measuring range Max of weighing can be divided without having errors of the cell(non-linearity, hysteresis, reproducibility in specified interval of temperatures) exceeded the maximum permissible error in given accuracy class of the cell. Deviation of correct value is denoted by verification intervals whose value is determined by relation: e = Max/n Minimal difference between measuring range of load cell and its rather greater rated load is advantegous from metrological point of view. Maximum permissible errors are given in fig.3, demarcating permissible deviations in verification intervals e for load cells in accuracy classes A, B, C.


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According to directive OIML the IR60 do not cross the maximum permissible errors of load cells when multiplying them by coefficient 0,7 of the maximum permissible error of electromechanical scales in accuracy classes I, II, III. Contrary to the force cells calibrated in N, kN the load cells are gauged in mass units (g, kg, t). They take into account gravitational constant in the place of calibration and the place of its use. Earth acceleration varies on the earth‘s surface up to 0,55%. This difference is negligible in the area of the Czech Republic in the same altitude. Load cells are generally the most demanding part of electromechanical scales in terms of longtime accuracy and reliability. Present-day electronics for measuring and signal processing from load cells comply to desired metrological parameters without problems. While metrological parameters of electronics are quickly verified by calibration circuits placed inside the device in service workplace for scales, the metrological parameters of load cells are verified after its disassembly in appropriate gauging laboratory which is costly and can for a time put the scale out of operation. Even though load cells of various producers comply to OIML recommendation they are not the same accurate, have different distance from limit of permissible errors and degradation process by its exploitation runs differently leading to lowered accuracy. Metrological characteristics of load cells are defined according to further introduced errors refered to its rated values.:

δL – linearity error is the highest deviation of the measuring signal from the idealy calculated beahaviour of measuring signal.

δH – hysteresis error is the highest difference between behaviour of the measuring signal from its zero values when load is raising up to its rated value and the beahaviour of measuring signal when load is dropping from its rated value to zero.

δR – reproducibility error is the highest difference amongst values of the rated measuring signal during repeated loading under the same conditions.

δt – fluxion error (elastic recovery) is the difference of the rated measuring signal at constant load of the cell and constant conditions in given time interval (e.g. 30mins) since the beginning of loading.

δTO – zero value error of the measuring signal of unloaded cell is its highest deviation in specified temperature interval from the zero value of the measured signal at reference temperature. δTJ – rated value error of the measuring signal owing to temperature is its highest deviation in specified temperature interval from the rated measuring signal at reference temperature.

δS – combined error includes errors δL, δH, δR.

When applicating present-day findings of science and technology the accuracy of load cells is in most cases limited by elastic recovery of its deformation elements.


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5.2 Practical example of a cell with parameters of SCHENCK RTN type In accurate electromechanical scales SCHENCK are used load cells of RTN type (see Fig.4) in the range of rated loads from 1t to 470t.

Principle of the deformation element of these cells is in Fig 5. When loading the cell in its measuring axis, outlined bending tension takes effect on the ring of the deformation element which leads to occurance of tangential tensions and therefore also to tangential deformations on the upper part of the ring in means of pressure (mean diameter shortens) and on the lower part of the ring by means of tension (mean diameter of this ring extends). Tangential deformations on both measuring surfaces of the rings are measured by four spiral coiling tensiometers in the shape of circular ring connected to complete and in all arms active Wheatstone bridge. Main metrological characteristics of load cells of the RTN type are shown in Tab. 1 for weighing temperature range from 10°C to +40°C. For extended weighing temperature range from -30°C to +40°C can be counted with worsened metrological characteristics up to 15 %.


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Cells produced in seven accuracy classes cover the need of standard industrial weighing, for exceptionally accurate trade weighing and the most accurate physical weighing. It is especially necessary to point out the low value of elastic recovery which by cells of higher accuracy classes is severalfold lower in comparison with all known load cells. In Fig. 6 is graphical evaluation of calibration results of the RTN type cell in accuracy class C4 Mi 7,5. Its metrological characteristics complies to the norm with substancial reserves. Two range RTN cells in accuracy classes C3 Mi 7,5 and C4 Mi 7,5 represent a novelty in the worldwide scale.


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A specific example is shown in Tab. 2 of their main technical and metrological parameters. At rated sensitivity of cells of the RTN type of 2,85 mV on one supply volt and at recommended max. supply voltage of 60V is the rated measuring signal of 170 mV severalfold higher in comparison with rated measuring signal of other known load cells.

The big advantage of load cells using deformation element according to Fig. 5 is the longterm stability of its metrological characteristics. Over ten years of exploitation these cells change only slightly and don‘t cross the maximum permissible error. An example is shown in Tab. 3 about change of basic metrological parameteres of RTD.1 load cell after seven years in service.

For completness it is necessary to mention that from the production of load cells of RTN type are being chosen cells called „Meister – Wagezellen“ designated for extremely accurate physical measurement, which have to comply to the éN 10002-3 norm, class 00, e.g. as standards in gauging devices for cells measuring forces, for measuring in aerodynamic tunnels etc. More extensive compensations and calibrations are carried out on these cells of higher accuracy in comparison with others. Present-day a new field is evolving in industrial weighing technology – mechatronics. Load cells are integrated into construction solutions of industrial products. Shapes of its deformation elements are usually unconventional. They serve as optimal part of construction solution as well as a load cell (see Fig. 7). Similarly was reviewed version of load cell with built-in electronics in comparison with described load cell of RTN type. The load cell of RTN type thus without built-in electronics


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appears preferable in light of metrology as well as practical standpoint of its installation into running.

Fig.7 Cell measuring load has the shape of functional part of technological machinery

5.3 Cells – division by output measuring signals Tensiometric cells may have different values of rated output (measuring) signal according to the type of construction of the cell. Earlier, when sensitivity of electronic evaluation devices didn‘t reach the possibilities of present-day electronics cells with high output signal were produced, e.g. 100mV / V. It means that on one volt of supply voltage brought to the cell was the difference of the ouput voltage at loaded cell to the nominal value rather high. Example: Cell constructed for 100 kg is supplied with voltage of 10V and its output rated signal is 100m V / V. If a force of exactly 100 kg impacts this cell the change of output voltage is 10 x 100 mV, i.e. 1 volt. When a force e.g. of 77 kg impacts the output voltage is 0,77 V above the level of output signal at unloaded cell. This was great advantage in times when electronic evaluation units didn‘t excel with high accuracy. Also today some producers produce cells of modern construction with high level output signal. Today’s types of modern cells have mostly output signal of 2 or 3 mV / V at recommended supply voltage of 10 – 15 V and also construction which enables replacement of original cell with cell from different producer / the same dimensions, gripping and spacing of holes, threads /. Output voltage of some cells mostly cheaper production is 1 mV / V. Impedance of cells: Most of today produced modern cells have input resistance 350 , 700 or 1100 ohm. Raising of input resistance is lead by producer’s endeavour to be able to parallely connect utmost cells so that the circuits of the evaluation unit which these cells supply are loaded as less as possible.


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5.4 Internal structure of a tensiometric cell

Characteristics of tensiometric cell are given partly by material and shape of cell, but mainly by type and accuracy of resistive tensiometer which is embedded into the body of the cell. In the year 1938 the first wire tensiometer was invented and so called foil tensiometers have been produced since the year 1952. Production of such tensiometers is difficult and only few companies around the world are able to produce these elements in top quality.

Foil tensiometer sticked on the body (HBM producer)

Owing to material is this one deforming. Deformations shows itself also on surface of the material. This change transfers to the tensiometer which in this way changes its resistance which is lineary equal to the extension on the material’s surface.

Basic type of foil tensiometer. In complete tensiometric cells from one to several pieces foil tensiometers are applied according to the type of cell and way of use. Quality tensiometric cells are produced with compensation of temperature influence and with compensation of creep owing to longterm load of the material.


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5.4.1 Examples of various types of tensiometers of HBM producer

Internal circuitry of tensiometer in 4 and 6 wires connection with compensations By direct sticking of these tensiometers onto the stressed material it is possible to watch the static as well as dynamic stressing of the material without interfering the structure of the material. Examples:

Detecting the change of direction of the tension when dynamically loading the ski Testing the mechanical stress of handle-bars of the bicycle


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5.5 Correct use of tensiometric cells in practise


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Correct use of tensiometric cells in practise – continuing:


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5.5.1. Principles for correct installation of cells


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Principles for correct installation of cells – continuing


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5.5.2 Principles for correct installation of cells – principles summary

Abidance of these rules is very important for scales contruction, which are supposed to show longterm accurate and stable weighing parameters.


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5.6. Individual types of cells / practical examples / There is a large number of different cells, which vary in terms of construction, characteristics and by its typical use. In the following part are introduced individual types of cells together with recommended use and with examples. 5.6.1 Single point – cell for eccentric load type Revere 652 This tensiometric cell is the typical representative of SINGLE POINT type cells. These cells are designated for direct mounting into the weighing bridges by means of screwing into the thread in the cell. It is a very robust cell for weighing bridges with dimensions 900 x 900 mm. Cells of this kind are not intended for parallel connection of inputs.

Cell of SINGLE POINT type is marked with this symbol. Cell is used to be placed in the middle of the weighing bridge so that both centric axes of the weighing bridge come through the centric axes of the cell. The cell is produced in a way that after placing the weight on any place of the weighing bridge the ouput signal from the cell is the same. These cells are produced roughly in the range of the rated weight from 3 to 1000 kg. Example of full label of the cell: REVERE 652 300 kg C3 (producer, type, rated load, accuracy class). Cells are produced in a way that in the place of screwing they have a mount (mounting area), which replaces the pad or they are without the mount and in this case it is necessary to install a pad between the cell and the base. As long as the cell would lie with its whole surface it cannot bend and would not work properly.


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Example of cell which does not have the raised mounting area is the cell HBM PW2C3. Producer recommends installation of mounting pads of 3 mm size.

Cell PW2C3 for weighing bridges up to 380x380 mm

Recommended mounting of a cell with distance pads

Way of transfering the force to the cells is by scales, which are defined as measuring tools, specified by WELMEC (European cooperation in legal metrology) recommendation according to the picture below and it is not recommended any other mounting.


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Example of technical catalogue list of a cell with complete data.


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5.6.2 Single ended bending beam REVERE HCB

Beam cells are one of the most widespread types of cells and have very universal use. These types of cells are used for production of all types of bridge scales with four cells, generally starting with dimensions of 800 x 800 mm and higher and weighing of 600kg and higher. They are convenient also for weighing reservoirs and lower forces or storage tanks. They are also convenient for installation into mobile scales or some types of aerial and special scales. They are used also for production or transformation of hybrid electromechanical scales. These cells are convenient for parallel connection onto the same conductor and mergence of its output measuring signal. At least 3 pieces of these cells are usually connected (this is given by the mechanical structure of the weight carriers) and at most cca. 10 pieces (this is usally given by specific properties of connected evaluation unit). Connecting merge modules are used for cross-connection of cells. These cells are produced in ranges roughly from 5 kg to 10 tons.

Cell REVERE HCB with adjustable shank for installation into bridge scale.

Beam cells are generally marked with these symbols. Cells are usually placed in the corners of the weight carrier or installed under underpinnings of feeding hoppers or tanks. They are usually mounted with two screws to a solid point (frame or weight carrier) and transfer of force to the cell is done at the point of axis of the third cell hole. Correct direction in which the force is going to take effect is usually marked with arrow. From opposite direction of the force the cell will not work properly. Seeing that these cells are in industry often deployed in the hardest conditions it is very important for these cells from which material are they made of and what industrial coverage are they placed into. Renowned producers produce these cells mostly in all-rustless design and in minimum coverage at least IP67.


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Way of transfering the force to the cells is by scales, which are defined as measuring tools, specified by WELMEC (European cooperation in legal metrology) recommendation according to the picture below and it is not recommended any other mounting. Plenty of other kinds of force transfers onto this cell exist since these cells are very universal.

Mounting which transfers force onto the cell must always be in a way that it provides certain clearance which ensures optimal transfer of force and also eliminates effect of forces and strokes from directions different than in the cell axis of impacting force. Different possible shape of beam cell: (REVERE SHB with adjustable shank)


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Examples of practical mounting of cells with correct force transfer:

Two examples of mounting (weighing of silos, tanks, feeding hoppers etc.)

Scheme of mounting by manufacturer Utilcell for beam cell, used as tensile

Other example of mounting by manufacturer Utilcell


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5.6.3 Double ended bending beam REVERE 5103

Double ended bending cells are not very common on the market, they are used more in special scales. However they can be well used e.g. also into automobile scales or for weighing larger forces and tanks. They are cells which are by means of construction solved in a way that they are mounted onto solid support on two spots and the force is transfered onto one spot (in the middle of the mounting spots) of the cell. As an example is the type REVERE 5103. Second version of double ended bending cell is when the cell is supported by one solid spot and the force is transfered to it in two spots which are the same distance away from the support mounting. As an example is the type REVERE 5223. Double ended bending cells are produced in higher rated values approximately starting from 2500kg to 125tons. These cells are convenient for parallel connection onto the same conductor and mergence of its output measuring signal. At least 3 pieces of these cells are usually connected (this is given by the mechanical structure of the weight carriers) and at most cca. 10 pieces (this is usally given by specific properties of connected evaluation unit).

Connecting merge modules are used for cross-connection of cells. Cell REVERE 5103

Cell REVERE 5223


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Double ended bending cells are generally marked with these symbols. Cells are usually placed in the corners of the weight carrier or installed under underpinnings of feeding hoppers or tanks. They are usually mounted with two screws to a solid point (frame or weight carrier) and transfer of force to the cell is done at the point of axis of the third cell hole. Correct direction in which the force is going to take effect is usually marked with arrow. From opposite direction of the force the cell will not work properly. Seeing that these cells are in industry often deployed in the hardest conditions it is very important for these cells from which material are they made of and into what industrial coverage are they placed. Renowned producers produce these cells mostly in all-rustless design and in minimum coverage at least IP67. Way of transfering the force to the cells is by scales, which are defined as measuring tools, specified by WELMEC (European cooperation in legal metrology) recommendation according to the picture below and it is not recommended any other mounting. Plenty of other kinds of force transfers onto this cell exist since these cells are very universal.

Examples of mounting of double ended bending cells: Mounting of cell REVERE 5103 Standard mounting of cell REVERE 5223


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5.6.4 Compression cell REVERE CSP-M (COMPRESSIONS CELL ) Compression cells are common on the market, they are cells designated for use in series of standard as well as special scales. However they can be well used e.g. also into automobile scales or for weighing larger forces and tanks. They are cells which are by means of construction solved in a way that they are mounted onto solid support on two spots and the force is transfered onto one spot (in the middle of the mounting spots) of the cell. As an example is the type REVERE CSP-M. Second version of compression cell is lower version e.g. type REVERE RLC (RING LOAD CELL), which thanks to its low construction offers construction advantages, however it is more demanding by means of its production. Compression cells are produced in higher rated values approximately starting from 1000kg to 470tons. It is possible to make a custom-made order by renowned producers of special compression cells with rated load of more than 500tons. These cells are convenient for parallel connection onto the same conductor and mergence of its output measuring signal. At least 3 pieces of these cells are usually connected (this is given by the mechanical structure of the weight carriers) and at most cca. 10 pieces (this is usally given by specific properties of connected evaluation unit). Connecting merge modules are used for cross-connection of cells.

Cell REVERE CSP-M 30 tons Cell REVERE RLC 28 tons

Symbol for classical compression cell Symbol for low-profile compression cell Compression cells are generally marked with these symbols. Cells are usually placed in the corners of the weight carrier or installed under underpinnings of feeding hoppers or tanks. Seeing that these cells are in industry often deployed in the hardest conditions it is very important for these cells from which material are they made of and into what industrial coverage are they placed. Renowned producers produce these cells mostly in all-rustless design and in minimum coverage at least IP68. This is very important, because for instance cleaning the space under the scale with water under pressure is part of automobile or wagon servicing which obviously afflicts also the cells. Pressure cells when installed according to producer’s recommendations are more resistive than other types against short-term overload and are characterized by its very good stability of parameters.


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Way of transfering the force to the cells is by scales, which are defined as measuring tools, specified by WELMEC (European cooperation in legal metrology) recommendation according to the picture below and it is not recommended any other mounting. Plenty of other kinds of force transfers onto this cell exist since these cells are very universal. Examples of force transfer onto the pressure cell:

Mounting of the cell CSP-M for silos or tanks RLC cells with adjustable shank


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5.6.5 Universal cell „ S“ for tension and pressure REVERE 9363 Universal cells of the „S“ type are not very common on the market, they are more likely cells for use in special scales. However these cells have a feature that they measure practically with the same accuracy both pressure as well as tension. Because they are mostly used for measuring tension they are commonly called „tension“ cells of the „S“ type. Example of such cell is the type 9363. Second version of such cell looks like a pressure cell but with help of the threads on bottom side it is possible to use them also as tension. Example is the type REVERE 42. Tension cells are produced in rated values starting roughly from 50kg to 35tons. For measuring greater tension forces are for technical as well as safety reasons used pressure cells which are built in construction reversor in order to measure tension. These cells are convenient for parallel connection onto the same conductor and mergence of its output measuring signal. At least 3 pieces of these cells are usually connected (this is given by the mechanical structure of the weight carriers) and at most cca. 10 pieces (this is usally given by specific properties of connected evaluation unit). Connecting merge modules are used for cross-connection of cells. Tension (universal) cell REVERE 9363 Universal cell REVERE 42 Note: It is recommended to cross-over these tension cells with copper conductor so that the remaining electrical current doesn‘t flow through the cell system.

Universal – tension cells are usually marked with these symbols. They are with advantage used for construction of hanging scales, reconstruction of mechanical scales onto hybrid (they are built into the last rod of the mechanical gearing) or for weighing hanging tanks or reservoirs.


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Way of transfering the force to the cells is by scales, which are defined as measuring tools, specified by WELMEC (European cooperation in legal metrology) recommendation according to the picture below and it is not recommended any other mounting.

Examples of shapes and use of tension cells: Tension cell Utilcell 650 Tension cell Utilcell 540

Tension cell Utilcell 25tons with recommended complement – upper loop and hook


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5.7 Digital tensiometric cells - principle Novelty among tensiometric cells are so called digital cells. They are actually cells described in previous chapters complemented with built-in analog-digital converter, circuits of internal calibration and curcuits of communication interface RS485. These cells on the outside appear to be classical analog tensiometric cells, however they have few advantages. Digital cells come out from production already calibrated and when replacing the cell one for another it is generally not necessary to perform new calibration beacuase individual units are by means of parameters identical and when every cell is loaded with same parameters they show the same characteristics. Next advantage is quick diagnostics of defective cell. Cells are connected with cummunication interface RS485 and evaluation digital unit communicates in MASTER–SLAVE mode. Small disadvantage is price of the cells as well as evaluation digital units for the time being. 5.7.1 Digital cell HBM FIT for digital weighing Digital cell HBM FIT is new front-end modern product which is besides digital converter embodied with unique oscillation damping and by this is designated for construction of very fast running scales. These scales are able to weigh on a running belt and evaluate several samples per second.

Digital cell with damping HBM FIT for ranges from 5–75kg

Graph of value stabilization of cell HBM FIT. Value stabilization and measure reaches after po 120ms .


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Complete technical catalogue list of the cell HBM FIT


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Examples of next digital tensiometric cells:

Digital cell REVERE SCC produced in ranges of 10 to 100tons

Digital cell REVERE SBC produced in ranges from 500 kg to 5tons.

Note: Electrical circuits in these illustrative photos are uncoverred for clearness. In practice the cells in the industrial cover IP66 – IP 68 and are tightly covered. Producers usually supply the cells with setup and diagnostic software which can work with all connected cells in real time at once. Example of connection of digital cells HBM C16i into the grid and subsequent connection to the PC


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5.8 Other types of cells for measuring force and weighing bodies Cells based on different principle than (how it is described in previous chapters) metal tensiometric bridge also exist. They are for instance induction cells, cells with electromagnetic compensation used in very accurate electronic laboratory scales or semiconductor tension cells. As an example of other type of cell convenient for construction of industrial scales we mention semiconductor cell. 5.8.1 Semiconductor cells of tension Microcell a L-Cell Principle of the cell: Cell is made of metal structure between which is mounted glass transverse girder on whose upper as well as lower side are implanted silicon crystals – semiconductor resistors. By pressing the cell it becomes to deflextion of the girder to the shape of bow and this way the upper part of ther girder shortens (lowering the resistance Ra), simultaneously with extending the lower part of the girder (raising the resistance Rb). This causes disbalance between two variable resistors. By its connection to other two resistors to complete Wheatstone bridge (located in the input part of the weighing unit electronics) the Microcell generates highlevel electric signal on the level of hundred milivolts (as much as 20fold compared to classical tensiometric cells) which is directly proportional to mass. Cells are connected parallely. High signal-to-noise ratio allows connection to ordinary triple-conductor shielded cable up to the distance of 600m. These cells are constructed as a „ Bolt – on“ in close translation as screwable.

Cell MICROCELL Cell L-CELL reads tension in two axes


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Technical list of cells MICROCELL:

Mechanical specifications

Load – level of tension

3‘‘ Microcell. Max. 7 kg/mm2

Recommended 3.5 kg/mm2 * +/- 1.75kg/mm2

2‘‘ Microcell. Max. 10.54 kg/mm2

Recommended 5.27 kg/mm2 * +/- 2.63 kg/mm2

* For different load please consult your distributor about recommedation of convenient type

Life cycle. 20 mil of cycles by pressure or tension of the cell from 0 to 3.5 kg/mm2

Electrical specifications

Excitation voltage. Standard 12 VDC. Max.30 VDC

Excitation current at 12V from 4.0 mA @ -18°C to 2.7 mA @38°C

Insulation resistance 2Mega-ohm

Puncture voltage of the cell against the cell’s frame >500V Impedance between red and black conductor. 4.0 K ohm, +/-1% @ 25°C

Impedance between red or black conductor against the white

3" Microcell. 8.54 K ohm, +/-1% @ 25°C

2" Microcell. 2.08 K ohm, +/-1% @ 25°C

Output (for 12V supply)

Sensitivity

3" Microcell. 70 mV +/-1%/0.7kg/mm2

2" Microcell. 56 mV +/-1%/0.7kg/mm2

Null load output. +/-25 mV max.

Non-linearity from full range. 0.1% prom full range.

Reproducibility and Hysteresis. +/-0.005% from full range.

Output impedance. 7.5K ohms (+/-1%).

Outer environment conditions

Covering. better than NEMA-4.

Temperature ranges.

Operational. -34°C to 60°C.

Storage. -34°C to 60°C.

Compensated. -18°C to 38°C.

Temperature changes Sensitivity change. 0.036 per Celsius degree in compensated range

Zero offset. 5mV per 56 Celsius degrees

Physical specifications

Weight. 90grams

Cable. 3-conductors, unshielded

Basic design. Carbon steel

For aluminium or rust-less design please contact distributor

Cable length. 1.7 standard (different lengths by request)

2" Microcell 3" Microcell 9.53 mm 9.53 mm A

(0.375 inches) (0.375 inches)

19 mm 19 mm B (0.75 inches) (0.75 inches)

44.45 mm 69.85 mm C (1.75 inches) (2.75 inches)

51 mm 76.2 mm D (2.0 inches) (3.0 inches)

Model Type

Sensor size

Sensor No. Description

M21L 2" 1 per girder Inside applications>7.0 kg/mm2

from full range at load

M22L 2" 2 per girder

Outside applications>7.0 kg/mm2


M31L 3" 1 per girder Inside applications<7.0 kg/mm2 C

onst

ruct

ion

gird

er

M32L 3" 2 per girder

Outside applications<7.0 kg/mm2

M22H 2" 2 per girder All applications>7.0 kg/mm2


M32H 3" 2 per girder All applications>7.0 kg/mm2 Con

strc

tion

cros

s-ba

r


Microcell cells are supplied with connection box, including terminal box and installation accessories

These cells can be used advantagously e.g. for weighing of silos, tanks or feeding hoppers, where it isn’t necessary to make any intervention to construction. These cells are screwed directly onto the supports or legs of the frame. It is possible to use them also for production of belt scales or batching scales.


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5.9. Test What is the dominant principle of cell production for measuring mass in the industry. Which tensiometric cell is not convenient for parallel connection of output signals. Describe the principle of MICROCELL cell. Calculate the size of output signal of tensiometric cell REVERE 652 500 kg when loaded with 100kg and when supply of cell is 10V. What is the difference between digital cells and classical analog tensiometric cells. Which types of tensiometric cells are convenient for measuring both pressure and tension. With how many conductors are connected classical tensiometric cells. List these conductors. How many conductors connection have the cells MICROCELL List 5 principles for correct installation of tensiometric cells. From what reason is the cell crossed-over with copper conductor when applicating tension cells.

Documents

WMT 5 - Module on Tensometric Cells EN V-101 301104 · active Wheatstone bridge. Main metrological characteristics of load cells of the RTN type are Main metrological characteristics