Herrera_ME455_Lab2

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Metropolitan Community College, Kansas City *

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455

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Mechanical Engineering

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Feb 20, 2024

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FALL2021. ME 455. Mechanical Engineering Measurements and Experiments Experiment #2. Load Cell Calibration Name: _Brandan Herrera_ Group Members: __Tanner Smith___ Lab Section: _Wednesday 10am-12:50pm_ Table #__3__ Section 1. Experiment summary (15 Points) ( 250 words) (Provide a summary of your experiment, including the following: the focus of the experiment, the instruments/sensors/setup explored, measurement(s) taken, data analysis done, one primary result, and one primary overall conclusion. Must be 250 words!) In this experiment, understanding how to calibrate a load cell (an "S" beam load cell) using the sequential calibration method was key to be able to use these instruments later in life. The calibration process involved assessing and calculating various errors based on collected data through the digital multimeter as well as the program LabView. By familiarizing ourselves with the LabView software, it is possible to understand the Wheatstone circuit with strain gauges. Understanding the calibration process is a crucial procedure in instrumentation measuring to ensure accuracy. The process involves comparing measurement values from a test with a known accurate standard, with another calibrated device. Being able to identify an error without adjustment was the end goal of this experiment. It is possible to convert force into an electrical output by utilizing strain gauges arranged in a Wheatstone bridge. By using modern measurement systems that are often used in computer-based data acquisition systems, it is possible to use the LabVIEW software to record these values. Being able to understand LabVIEW, which is widely used for digital measurements, analysis, and control of test systems, it is possible to find ways to make items better as a mechanical engineer and show physical proof.
Section 2. Recorded data (5 Data Table: 8 Points each) Table 1: Data from OMEGADYNE Specification Shee t Specifications for the load cell Static Sensitivity 1.201 mv/lbs Linearity 0.03% FSO Hysteresis 0.02% FSO Zero Balance 1% FSO Repeatability 0.01% FSO FSO 30.0144 mv Table 2: DMM vs. LabView Voltages before/after amplifier Equipment Before Amplifier After Amplifier Calculated Gain % Error (DMM as Base) DMM 0.079 10.16 128.61 N/A LabView N/A 10.15 128.48 0.1 Table 3: “Calibration” of Weights (Include Weighing Error Estimate) Measurement # Designation on Weight or hanger/bucket (e.g., ME455-001) Weight from Digital Scale (lbs) 1 2.5 2.495 2 5 5.33 3 7.5 7.825 4 10 10.395 5 12.5 13.07 6 15 15.64 7 17.5 18.17 8 20 20.76 Table 4: Sequential Calibration Data from Load Cell Test #1 LOAD CELL DATA Sequence Data Pt. Load (lbs) Voltage (V) UP 1 0.000 (no hanger/bucket) -5.002 2 ~0.000 (hanger/bucket) -4.825
3 ~2.5 [2.495] -3.920 4 ~5.0 [5.33] -2.898 5 ~7.5 [7.825] -1.979 6 ~10.0 [10.395] -0.968 7 ~12.5 [13.07] -0.053 8 ~15.0 [15.64] 0.874 9 ~17.5 [18.17] 1.819 10 ~20.0 [20.76] 2.754 D0WN 11 ~17.5 [18.17] 1.825 12 ~15.0 [15.64] 0.8798 13 ~12.5 [13.07] -0.052 14 ~10.0 [10.395] -0.969 15 ~7.5 [7.825] -1.979 16 ~5.0 [5.33] -2.886 17 ~2.5 [2.495] -3.920 18 ~0.000 (hanger/bucket) -4.83 19 0.000 (no hanger/bucket) -4.396 Table 5: Sequential Calibration Data from Load Cell Test #2 LOAD CELL DATA Sequence Data Pt. Load (lbs) Voltage (V) UP 1 0.000 (no hanger/bucket) -5 2 ~0.000 (hanger/bucket) -4.8 3 ~2.5 [2.495] -4 4 ~5.0 [5.33] -2.9 5 ~7.5 [7.825] -2
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6 ~10.0 [10.395] -1 7 ~12.5 [13.07] -0.1 8 ~15.0 [15.64] 0.9 9 ~17.5 [18.17] 1.8 10 ~20.0 [20.76] 2.8 D0WN 11 ~17.5 [18.17] 1.8 12 ~15.0 [15.64] 0.9 13 ~12.5 [13.07] -0.1 14 ~10.0 [10.395] -1 15 ~7.5 [7.825] -2 16 ~5.0 [5.33] -2.9 17 ~2.5 [2.495] -3.9 18 ~0.000 (hanger/bucket) -4.8 19 0.000 (no hanger/bucket) -5 Table 6: Sequential Calibration Data from Load Cell Test #3 LOAD CELL DATA Sequence Data Pt. Load (lbs) Voltage (V) UP 1 0.000 (no hanger/bucket) -5.001 2 ~0.000 (hanger/bucket) -4.873 3 ~2.5 [2.495] -3.964 4 ~5.0 [5.33] -2.800 5 ~7.5 [7.825] -1.930 6 ~10.0 [10.395] -0.950 7 ~12.5 [13.07] -0.049 8 ~15.0 [15.64] 0.869
9 ~17.5 [18.17] 1.825 10 ~20.0 [20.76] 2.754 D0WN 11 ~17.5 [18.17] 1.832 12 ~15.0 [15.64] 0.872 13 ~12.5 [13.07] -0.049 14 ~10.0 [10.395] -0.973 15 ~7.5 [7.825] -1.984 16 ~5.0 [5.33] -2.892 17 ~2.5 [2.495] -3.930 18 ~0.000 (hanger/bucket) -4.825 19 0.000 (no hanger/bucket) -4.402 Section 4. Questions (5 Points Each) Suggest to use a MATLAB code to calculate the parameters requested and for submitting the code and answering the following questions. Answer the following questions, and submit graphs and tables, as well as your MATLAB code as appendices if there is. Note: Remember the load cell signal has been amplified by a gain of ~333 or ~500 . 1) Calculate the static sensitivity of the load cell based on your data. Compare this to the value provided by the manufacturer. If different, how much and why? The value provided by the manufacturer is that the amplifier is a 1.20 mV/load amplifier. Based on my calculations using the equation 𝑆𝑡𝑎𝑡𝑖𝑐 𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦 = ∆ை௨௧௣௨௧ ௌ௜௚௡௔௟ ∆஺௣௣௟௜௘ௗ ௅௢௔ௗ , I got a mV rating of 3.73 mV/lb which is off by at least 2.53 mV. This is the case because it is the most ideal situation that they get the 1.2 mV/load as well as it is in a controlled environment but in a regular lab it may not be the only thing effecting it. It also might differ if there is a smaller load difference between the two weights and they can get the weights closer than not. Another issue is that the load cell could have been through higher stresses over the course of when it was first bought so calibration might be a bit off or sensor is worn out.
2) Calculate the maximum linearity error of the load cell based on your data. Is this within the specified tolerance given by the manufacturer? If not, suggest why? By taking the differences between the points at each weight we can figure out the maximum linearity error of the load cell could be to which the maximum that was calculated was after the weight was removed and it was just left with a difference of around 0.601 V. This is a little out of the specifications but the issue that could have happened was wear and tare of the load cell which over time it can give a different variation depending on how long it has been serviced and recalibrated. 3) What is the zero balance error for this load cell? Is this within the specified tolerance given by the manufacturer? If not, postulate why? To calculate the zero balance error we will use the equation of Zero Balance error = |𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑂𝑢𝑡𝑝𝑢𝑡 ଴ ௅௢௔ௗ − 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑒𝑑 𝑂𝑢𝑡𝑝𝑢𝑡 ଴ ௅௢௔ௗ | which gives us the value of 0.285. This is close to the tolerance specified by the manufacturer but still because of the time that the load cell could have been maintained, it probably was not which for the future it would give future teams issues and values that are not close to what the manufacturer specified if it was bought brand new. 4) What is the hysteresis error for this load cell? Is this within the specified tolerance given by the manufacturer? If not, postulate why? By using the equation to find hysteresis (Hysteresis Error = |𝑀𝑎𝑥 𝑂𝑢𝑡𝑝𝑢𝑡 − 𝑀𝑖𝑛 𝑂𝑢𝑡𝑝𝑢𝑡| ) we can find that the error for this certain load cell is 7.755 V. This is within the specified tolerance because the error on the load cell is ±0.02% FSO so it fits in the specifications that the load cell has. Section 5. Conclusions (2.5 Points Each) (~100 words) Did the group complete the goal of the lab? Stating yes or no is insufficient for labs with more data driven goals. In this exercise’s case the goal is get “hands on” experience with the data analysis of wave functions and gain an understanding of the types of errors that can occur when sampling incorrectly. The group completed the goal because the group was able to apply a load and be able to use the LabView program in order to transfer a mass to a voltage using an S block. By being able to see how using an amplifier along with an S block to measure the voltage allows the group to be able to get numerical values and if need to plot the data. This also allowed us to be able to find some errors in the end solution because when weighing the weights, there was some sleight variations of the weights such
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as when weighing the, what was suppose to be, 5 pound weight. The actual weight of the weight was around 5.33 pounds which in a general purpose use it is not that much of a difference but in the experiment it plays a huge role in variations of the final results which means that there was either some error in our final results or there was an error in the manufacturer’s results since they were not used with the same amount of weight or there was some variations on both the weights. What would you change about this lab? What data (if any) could you not obtain? Be specific as to the reason you would change the lab. If you feel that you didn’t meet the criteria for success on this lab how might you change that? If there was something I would have liked to see is use LabView to be able to see different values other than voltages. I would guess that we will be using LabView to find voltage differences in the future but being able to get a grasp on how to use LabView would be better for this experiment. I also would have a shortcut on the computers for lab view or a step by step on how to open lab view because not everyone has used it before so knowing where it was is half the time of class.