Force Measurment System Based On Strain Gauges Engineering Essay

Force Measurment System Based On pedigree Gauges Engineering EssayIn this subprogram at that place willing be a employ of a examine standard of measuring device which experiences a change of electric opposite when it is assayed. purport, build and test a draw off sen faultg element development blood gauges argon provided, as sanitary as development of the appropriate combination of strain gauges with other electrical ing goingients to line up an electric potentiality or contemporary representing tensile, compressive or bending strain, unneurotic with means of displaying and/or recording its think of, is a strain gauge system.TasksDesign and build a strain gauge ground describe sensor based on a preservetilever purport or otherwise. human body an appropriate VI that can be employ to carry place in all(prenominal)(prenominal) tests on the sensor. experimentally evaluation of the rig/force reposition functions of the sensor. Include linearity, hysteresi s, sensitiveness, accuracy and repeatability in the evaluation.Calculation the expected theoretical produce set of the sensor and compression them with the experimental results obtained to a higher place.Investigate the effect of temperature on the accuracy of the sensor. Based on this investigation suggest a temperature allowance scheme to improve the per put to get toance of the sensor.Build an appropriate VI that trails the end product of the sensor and display the result in appropriate units.Part IExplain how the AC Power (wattmeter) measuring is carried out at NPL. cast a oppose p good deal of the measuring rod system use. You should include the bugs of uncertainties in your discussion.Volts, Amps, Watts, VARs and Power Factor argon essential fundamental quantities which must be mensurable accurately in collection to optimize the control and bringing of electric jacket crown executive.Definition of electrical military forceAt a stipulation second gear, when a veri hold over i travels from reference G to receiver Rin the pedagogy defined by the potential v delivered by the generator (figure 1), the instant(prenominal) power supplied to the receiver R is correspond to produce v.i. name author ReceiverIf the potential and current be DC, the mean power V.I is equal to the instantaneous power V.I. If the voltage and current be sinusoidal AC, in that respect is generally a phase shift amongst the voltage and the current (figure 2).The instantaneous value of voltage v and current (I) have the formv = V slime romaine lettuce ti = Imax cos (t )Where , the pulse, is comparative to the absolute frequency F ( = 2F). emblem phase shift amid the voltage and the currentThe instantaneous power has a value of Vmax . Imax . cos . cos (t ). You must take the average value of this product during a period to obtain the expression of the power provided by generator G to receiver R. This power is called the active power and is express b y the formulaThe wattmeter provide the expression of this product, either by causing a deviation of the pointer in the case of a device with an electrodynamics wretched coil, or by supplying a DC current or a voltage proportional to the product in the case of electronic wattcmeters this current or this voltage is because applied to an analogue or digital display.The existence of a phase shift between the current and the voltage leads, for AC currents, to the introduction of 3 additional quantities- The apparent power S = Veff . Ieff, in VA (volt-amperes), defining the voltage Veff not to be exceeded (insulator break charge, development in core loss) and the intensity Ieff circulating in the receivers.- The power factor inWhen the current and voltage are sinusoidal quantities- The reactive power Q = Veff . Ieff . sin , in rva (reactive volt-amperes).The latter may be directly measured by a wattmeter if for voltage Vmax . cos t we substitute a phase-shifted voltage of /2, i.e. Vm ax x cos (t /2).The mean product measured will be Vmax . Imax . cos (t /2) x cos (t ) which is expressed byVmax. Imax Q = cos (/2 ) = Veff . Ieff . sin 2Knowing P and Q, we can calculate the apparent power and the power factor unornamented power S = P2+Q2Power factor PF = P/S = P/P2+Q2Knowing the parameters defined above active power, reactive power, apparent power, power factor, is fundamental in electrical engineering and enables accurate calculation of the characteristics of the equipment utilise yield, load, cos , utilization limits. The wattcmeters used for these measurements are classified in trine major families electrodynamics and electronic.Digital Sampling Watt MeterIn NPL the digital try out AC wattcmeters, which are used for calibration work, each pick out the generation of sample timing pulses suitably locked to the frequency of the AC which is to be measured. Repetitive waveforms representing the instantaneous test voltage and test current are digitised at eq ual time intervals of time harmonically related to the period of the waveforms. A new NPL standard wattmeter calibrator incorporates improved sample timing generation. It uses a crystallization digital oscillator to govern both the sample timing and the AC source frequency. This avoids reliance on timing interpolation uniformity within an introduce period only digital frequency dividers are needed. Alternatively, commercial frequency synthesizers can be used, with a common master frequency, to give sampling and signal frequencies. Either alternative allows digital phase control, and reduces the use of special-purpose clearcutness analogue electronics.AC power wattmeter and voltmetersFigure AC Power amount by samplingPower measuring at NPL is based on a digital sampling technique. This works by using a pair of analogue to digital converter (ADC) to take instantaneous samples of the several(prenominal) voltage and current waveforms involved in measuring by multiplying the patte rn pairs, the instantaneous power can be established and by averaging instantaneous over a defined interval the average power of that interval can be arranged.Figure Sampling WattmeterThis technique relies on the capital punishment of the ADC in terms of its exactness and its ability to take samples at light instant in time. To meet these requirements NPL has developed an ADC system based on the fastest shape of ADC, lastn as a blaze converter. Unfortunately, these devices are of circumscribed resolution and to overcome this limitation they are included in configuration that uses a Digital to Analogue Converter (ADC). This organized unanimous makes employ the repetitive properties of the waveforms of attention where single rape is extremely akin to the spare-time activity round.Figure Phantom PowerThe computer takes a guesswork at the signal level at a stated moment on the waveform. This digital guess is accurately born-again to voltage using the DAC. The guess can then be compared to the incoming signal at the required dot in time and the mistake voltage is converted using the blaze converter and passed back to the computer. Because the waveforms are assumed to be repetitive the computer can improve its say for the following(a) round of the waveform using the mistake knowledge from the former round. In this carriage the computers conjecture converges on digital reproduction of the input waveform. This reproduction can then be used for AC voltage, current measuring.Figure NPL ADC nonrepresentationalTwo of these ADC systems are used for single-phase measuring. They are used in conjecture with transducers that change unlike levels of voltage and current to the working signal levels of the ADCs. In organization to present traceability all of these components require single calibration and characterisation. misgiving ContributionAny estimation of uncertainties must start by identifying all significant contributions. There may be several sources of wr ongful conduct in a measurement where the magnitude of the error could be quantified. Where these can be identified, they should be corrected such that only the residual unknown component contributes to the uncertainty of the measurement. Using the importation of DC voltage from a higher(prenominal) level laboratory as an example, there will be the following uncertainty components standardisation UncertaintyTransportation constancy with TimeStability with TemperatureNoiseUsually the measurement techniques used will ensure salubrious defined conditions and minimize essence effects such that the main contributions listed above will be the only significant ones.Calibration UncertaintyCalibration uncertainty is a significant contribution and is usually reported on the certificate of calibration issued by other organization i.e. the national laboratory. kind of reasonably, the national laboratory is beyond the control of other commercial organizations and there is little that can be done by the customer to valuate the uncertainty reported as a single value on the certificate. For this reason the calibration uncertainty is usually treated as a type B contribution. The reported uncertainty may vary jolly for each calibration and will usually be at a 95% minimum confidence level.Part IIForce measurement system based on strain gaugesIntroductionA pocke flurry product based of strain gauge is contriveed in this part of the assignment, force measurement based on strain gauge. Two strain gauges committed properly on each side of a brand name cantilever these two strain gauges are a part of a resistance combination called Wheatstone bridge supplied by 5V. The outfit of this enlistment connected to data encyclopaedism card through an amplification locomote. A depressive disorder pass filter overlap provided. The circuit has been designed and calculated then built on a PCB supplied by power supply device. besides the circuit has been tested and practically o perated using suitable burdens (UK 1 cent to 10 pence) ten coins have been used. Data acquisition card used to pass the results to the computer. LabVIEW software was the tool used for monitoring the results. fund gaugeAs an external forces applied to an object, this will produce a essay and strain. That means the metal object will be compressed and the resistance of the metal will increase, while the resistance will decrease if the metal stretched. By using this feature of a specific metal force measurement sensor bas been built. This called strain gauge. The design of a force measurement system was based on strain gauges because as the name implies they are used for measurement of strain. The strain gauge is attached to the object by a suitable adhesive, such as superglue as battle arrayn belowStrain gauge mounted on component under testFigure strain gauge glued on cantilever1Strain gauge operationGenerally electrical resistance (R) of a metal fit is proportional to the length (L) and inversely proportional to the area (A) as accustomed by (where is the resistivity).The change in resistance in a strain gauge of resistance R is nearly proportional to the applied strain. ref9 thuslyK is constant known as the gauge factor which is the sensitivity to strain.Strain . The gauges used in this report have K=2100.02Figure (2) shows loaded cantilever BeamSG 1SG 2LFXFigure stain gauge keep mum plat2The gauges are glued at a distance (L-X) from the load, a load of trade m and weight mg is suspended from the cantilever beam. The beam has thickness t and width w and is made from stainless vane with a young modulus. The calculated strain due to the suspended mass is. thence the relative change in the resistance of the strain gauge is apt(p) by.Wheatstone nosebandThe change of the resistance of the strain gauges is real down(p) so the strain gauges have to be connected in a Wheatstone bridge shown in figure (6). The gauge glued on cover of the beam is in ten sion, the gauge glued underneath the beam is in compression, hence strain causes equal and opposite resistance changes in the gauges. By using two gauges the effects of temperature regenerations on the gauge resistance are cancelled.The bottom end of the bridge circuit is connected to the ground, the circuit is power by the bridge excitation voltage VEX applied to the top side of the bridge.Figure Wheatstone bridge3If the strain increases the resistance of Gauge ace from R to R + then the resistance of Gauge Two is reduced from R to R . Hence the voltage VG is given byTo equipoise the Wheatstone bridge the Zero Adjust resistor is adjusted to produce a voltage of VADJ . ref11 Therefore the outturn voltage V0 of the Wheatstone bridge is given bySubstitutingThen locomote design detailsFigure Circuit designThis circuit is designed and built by a team of three students and its a number of stages as shown in the block plot belowTwo strain gauges connected on a Wheatstone bridge. ref inement circuitLow pass filter circuit (RC circuit).Data acquisitionLabVIEW software based on ComputerStrain GaugesWheatstone bridge involution CircuitFilter (RC)D.AQComputer ScreenFigure circuit block diagram face onePre-circuit has been designed and built which is consists of two strain gauges of resistance of 120 of each glued on the cantilever. Wheatstone bridge provided with R1,R2 of 1k of each and powered by 5v. The figure below show the circuit diagram of first stage.Figure First stage circuit connectionThe circuit above is a half bridge while the sidetrack voltage will be asand the object that are used to be measured by the strain gauge sensor is the UK pennies as shown in figure and the mass for it is 3.5 gram.Calculations bridge output voltageL = 140mm,x = 50mmw = 8mmt = 0.5mmE = 210GpaG = 2The maximum loading force that the Cantilever can handle isWhere is the Fatigue strength for steel?Since,Then,Kgm = 204 gramSo the maximum mass that courses the max force is 204gramS inceG=2Vs=5VSoThen0.219485 mV0.43897 mV0.658455 mV0.87794 mV1.097425 mV1.31691 mV1.536395 mV1.75588 mV1.975365 mV2.19485 mVThe following table shows the calculated valuesCalculated valuesNo of coins large number (gram)0013.527310.5414517.5621724.5828931.51035The figure shows the simile between the mass of the coins and the calculated output voltage of the bridge circuit. map 1. The apprisal between the mass and O/p voltagesSecond StageIn this stage an amplification circuit is needed in order to increase the output voltage to a range of 0 10 v as an input to the data acquisition, INA126 OP AMP has been used with a gain resistance of around 80 ohms to get a meter amplification ratio, the following figure show the op amp circuit diagramFigure Op amp circuit diagramAccording to the data sheet, and from the table shown above the gain of the circuit can be adjusted by varying the Gain Resistor RG. The gain 1000 needed could be done by using or adjusting the gain resistance RG to be 80. 4 (variable resistor has been used).And the following calculations proves the value of the Gain Resistor RGSinceSothird stageFigure Low pass filter circuitAs show in circuit diagram, an RC filter with a components of C= 22uF and R = 10 k ohms. The calculation below shows that this filter values is above the maximum frequency of the expected values from the dc components and to guarantee to get rid of the voltage spikes.The frequency value is about 1 Hz.Measuring the Bridge output voltageAs the circuit has been connected, start measuring the output of the Bridge circuit for each number of coins.Measurement valuesNo of coinsMass (gram)0013.527310.5414517.5621724.5828931.51035And the chart bellow shows the parity between the mass of the pennies and the measured output voltage of the bridge circuit.Chart 2. The relation between the mass and O/p voltagesThe chart above shows the relation between the mass of the coin with the output voltage values, it can be clearly seen that there is a non-linearity with the chart and this caused by the non accurate measures. The red line is the trend-line which used to simulate the real linearity for the chart.The following table shows the results of the output of the amplification circuitMeasurementNo of coinsMass (gram) fruit of the Bridge in (mV)00013.50.20270.41310.50.624140.83517.51.126211.42724.51.578281.78931.51.9310352.21Experimental proceduresProceduresConnecting and implementing the circuit as shown in the circuit connection scrutinying the circuit if its workingMake sure of the output of the bridge is set to 0V. cast the coins (penny) on the beam and observe the output of the circuit, if the circuit it works, go to next step.The bellow picture shows the penny which has been used as the weights to be measured in the experiments. The weight of this penny is 3.5. That should be taken into account in the calculations.Figure UK PennyData acquisitionLab View has been used to simulate the operation of the circuit. Lab view i s a measurement screening which uses a variety of data acquisition hardware. The following Figure shows the block diagram consisting of the DAQ assistant and some numerical representation of the number of coins and weight in grams with the ability to adjust the offset.The bellow pictures showing how the practical work had been carried and what stage we did carry to finish this piece of workIntegrating all the circuits had been justified and connecting the output to the LabVIEW by the data acquisition. LabVIEW screen shots below show the real practical results of the circuitFigure LabVIEW simulationOutput values with no load on cantileverFigure output value with on loadScreen shots for some valuesWhen taken the results another test has been done by exchange the cantilever upside down and negative results found. And the following LabVIEW screen shot result show the output voltage with 10 coins on, with both negative and positive resultsFigure output of 10 coins (negative and positive )Results and AnalysisNoof coinsTest 1Test 2Test 3Test 4Test 5Test 6Test 7Test 8Test 9Test 10Mean (Average)Standard Deviation10.200.240.230.210.220.230.240.250.260.200.2280.0204420.410.470.430.420.390.380.410.440.490.420.4260.0337330.620.710.690.640.630.620.650.640.630.610.6440.0320440.830.780.810.830.830.820.790.720.750.820.7980.0379551.121.211.181.191.091.051.171.161.151.111.1430.0496861.421.371.341.251.231.221.281.181.211.411.2910.0874971.571.811.791.711.641.621.671.661.611.561.6640.0846281.801.791.811.771.691.671.691.631.671.811.7330.0692991.931.992.012.051.991.991.891.931.971.921.9670.04855102.212.292.322.282.202.262.162.262.102.212.2290.06624Maximum Experimental ErrorThe maximum experimental error in the expected value of Vo using the formulaThe error in our application was acceptable and its expected, many factors may require the results especially temperature affect as the strain gauge based on resistance variation of the metal which affected by temperature.Self evaluationDu ring working on this mini project I have learn a lot according to sensors application specially strain gauges application, and how we could make use of the sensors and how to design a circuit by choose the suitable components as come up as improving the output results of the circuit. With the help from the tutor Dr Ahmed we succeed to design and built the circuit.The team which I was involved to do the work with was very(prenominal) good as very accomplish to finish the work as soon as possible. Working on teams has so many advantages as the work would be split to save the time. The designing and the building for the circuit didnt take much time, by the time we finished the design we started to take the measuring and the readings for the outputs.Working on new software like the LABVIEW was very challenge because its the first time for me to get use to this software and a very hard work has been taken to carry some tutorials and know how the software is work. As this software is ve ry wide in use and has everything that the engineer can have the benefit from the use of such tremendous software.ConclusionA mini project has been designed and built based on strain gauge trying to perform what it is regarded as primary function like measuring the weight. Stain gauges are quite ingenuous in design. The circuit diagram of the design was designed in the MULTISIM electronic workbench software.All components were calculated to get suitable values as well as a typical calculation has been done for the results. The measurement values compared with the calculated values and a very small diametrical was provided as this is expected and acceptable.Lapview tool was the best software to simulate the output of the circuit where the output can be clearly achieved as well as we could multiply, divide and/or add factors to the output results value.