Measurements Definition and 397 Threads

Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International vocabulary of metrology published by the International Bureau of Weights and Measures. However, in other fields such as statistics as well as the social and behavioural sciences, measurements can have multiple levels, which would include nominal, ordinal, interval and ratio scales.Measurement is a cornerstone of trade, science, technology and quantitative research in many disciplines. Historically, many measurement systems existed for the varied fields of human existence to facilitate comparisons in these fields. Often these were achieved by local agreements between trading partners or collaborators. Since the 18th century, developments progressed towards unifying, widely accepted standards that resulted in the modern International System of Units (SI). This system reduces all physical measurements to a mathematical combination of seven base units. The science of measurement is pursued in the field of metrology.

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  1. M

    Error propagation question - when do we combine repeated measurements?

    Hi, say I measure something ten times and get x+d1x, x+dx2, ... where dx1, dx2.. are the measurement errors. Now, say I want to calculate something from these measurements according to: A = B(C(x)), Where A is what I want, and B and C are known functions. Which is statistically...
  2. Q

    Measurements in Quantum mechanics

    Ok so I'm currently revising my quantum theory course from this year and I've reached the section on the postulates for measurements in quantum mechanics. The one I'm having trouble with is "The only result of a precise measurement of some observable A is one of the eigenvalues of the...
  3. S

    Observables, Measurements and all that

    Hi Folks, I somehow cannot get the difference and have to admit that I am left confused. For a probability of measuring m with the operator M on state \Psi_i p(m|i) = <\Psi_i| M^{+}_m M_m |\Psi_i> = <\Psi_i| M_m |\Psi_i>. The average of an observable is defined as <O> = <\Psi_i| O...
  4. V

    Imperial measurements just feel better

    Metric holds an advantage in simplicity, but imperial seems to have better unit amounts. For instance, temperature. I cannot think in celcius. 60's weather is 15-20 celcius. 70's is 20-26 celcius. 80's weather is 27-34 celcius. Lengths: a mile is a significant accomplishment for human...
  5. T

    Sensitivity and Uncertainty in measurements

    Greetings fellow members, I have some queries on a laughably rudimental topic regarding measurements. Say you have a metre rule with sensitivity of 0.1cm, and you are measuring a wire which stretches from the 0.0cm starting point to the middle point between 7.3 cm and 7.4cm. My...
  6. S

    Engineering Balanced star connected circuit measurements

    Measure phase and line voltages. Measure currents in the three lines and neutral. Measure total power dissipated in the load. Calculate total apparent power absorbed by the load. Determine power factor. Draw phasor showing voltages and currents.P=P1 + P2 Q = √3(P2 - P1) |S| = √(P2+Q2) θ =...
  7. H

    Ellipsometric measurements on a mirror.

    Hi, During my internship I worked with an Ellipsometer. Now I'm wondering, what values of Psi and Delta do you get when you measure a mirror under an Ellipsometer? Are there any phaseshifts at all? Because there are no layers on the mirror right? It's fully reflective in total.. Hanna
  8. trollcast

    How Do Measurement Uncertainties Impact the Calculation of Gravity?

    Homework Statement The experiment set up is a steel ball bearing is held from an electromagnet and above a switch at the bottom. When the electromagnet is switched off a timer starts and stops when it hits the switch. The height from the bearings initial position to the switch is measured...
  9. Q

    Quantitative Measurements for the Higgs Boson

    Hi everyone and happy New Year. The Standard Model shows very specific and measurable couplings of the Higgs boson with the W and Z fields. What QUANTITATIVE measurements have been done to verify that these couplings are as predicted? Thanks and looking forward to your replies. A lot of...
  10. O

    What are the correct labels for the variables in the bar chart?

    I need to drag and drop all the labels into the relevant boxes by the bar chart. Three spaces will be left empty because there is anything to describe them. (See the attachment) I was thinking: title empty empty smalles difference between ... empty independent variable dependent variable...
  11. A

    Uncertainty of distance measurements for regions between 50-250 pc away

    Hi, I am in the middle of a project dealing with the mass loss rate of protostars and hence I am working with the distance that these sources are away from us. I need to find the error in these distance measurements, however I cannot. In any paper (I find) that cites distances it just gives...
  12. S

    Successive Measurements of angular momentum

    Hello, I believe this to be a rather simple problem but I am not quite sure if my thinking is correct. We have a particle in a j=1 state of angular momentum J. I am first asked to find some eigenvectors of the matrix J(y): J_{y}=\frac{\hbar}{\sqrt{2}i}\begin{pmatrix} 0 & -1 & 0\\ 1 & 0...
  13. B

    Resistivity measurements of a circular shaped sample

    Hai, I am doing my masters degree in physics. can somebody help me in which formula to use for calculating resistivity of a sample of circular shape using two probe measurements, which should include thickness and correction factor also. Thank You!
  14. C

    Books on Experimental Methods, Instruments, and Measurements

    I'm looking for some good quality books on experimental methods, instruments, and measurements for graduate level. Do you guys have any recommendations?
  15. J

    How to make Resisitivity vs. Temperature graph from in-lab measurements

    We used a wheatstone bridge, which is an electric circuit consisting of four resistors.Two of the resistors are known, one resistor is a large "resistor" with dials that control the resistance, and the fourth resistor can either be a metal or semiconductor. The metal was heated to about 290 °C...
  16. J

    The HUP, simultaneous measurements, and eigenfunctions

    Hi everyone, I know this topic has been discussed quite a bit -- and in particular it's been done in this thread and this thread. But there are still some things I want to talk about in order to (hopefully) clarify my own thoughts. One of the threads discusses this Ballentine article in which...
  17. U

    Multiple Electron Spin Measurements

    Homework Statement The z-component of the spin of an electron is measure and the value h-bar/2 is found. Immediately afterwards, the spin along a direction making an angle θ with the z-axis is measured. What are the possible outcomes of this second measurement and with which probabilities do...
  18. S

    Errors in Measurement: Types, Sources & Comparison

    Here's what I understand... Types of errors 1.Systematic errors Zero Error errors due to slow stopwatches errors due to incorrectly graduated scales 2.Random errors error due to unevenness of the measuring item parallax error Ways of comparing errors Absolute...
  19. Y

    Sine Wave measurements vs equations

    I have the equation E(t)=7*sin(11000t+∏/3) and I measured the following: E(.22ms) = .422V Frequency = 1.751kHz Period = 572.0 μs Peak = 7V Peak-Peak = 14V E(rms) = 4.8V E(average) = 105mV I've calculated the following to compare E(.22ms) = .422V Frequecy = 1.75 kHz Period...
  20. bohm2

    Bohm trajectories and protective measurements?

    Bohm trajectories and "protective" measurements? I'm having trouble understanding the arguments presented in these papers. They seem to be both arguing against the de Broglie-Bohm theory bassed on the concept of "protective measurements". Is this just a rehash of the problems with the meaning...
  21. P

    Why Did Aristarchus Measure the Sun's Distance During a Half Moon?

    1. Why did Aristarchus make his measurements of the Sun's distance at the time of the half moon? Aristarchus watched for the phase of the Moon when it was exactly half full, with the Sun still visible in the sky. Then the sunlight must be falling on the Moon at right angles to his line of...
  22. R

    Early 1900's Concentration Measurements

    I have read a few papers that were written in the early 1900's where their concentration measurements are M/4, M/8, M/16, M/32, M/256. I am not sure what this means and I was wondering if anyone could relate these concentration measurements to normal concentration measurements we use now, such...
  23. B

    Determining XY coordinates from quadrilateral measurements

    I'm trying to determine the XY coordinates of 3 corner points of a quadrilateral shape based on known lengths of the sides of that shape. I know the lengths of all 4 sides of the shape as well as the lengths of both cross lengths (effectively making two adjacent triangles). I've attached a...
  24. J

    Theoretical Aspects of Measurements

    I work for a drug company & they have a department of Metrology - "Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement." Anyways, so what exactly are the theoretical aspects of measurement? To me, they would be something like...
  25. L

    Do gravitational waves affect our measurements of weight?

    Hi, it's my first post here, though I've long viewed these forums without a registered account. I was thinking about gravitational waves, and what exactly they would do. From what I understand, these waves affect everything with mass in the universe. The force they exert is exponentially...
  26. E

    Uncertainty in group of measurements, given single measurement uncertainty.

    Hello! I have a question regarding measurement uncertainties. This is not a homework problem. Let's say that I want to measure some quantity, and I want to measure it multiple times using multiple identical but separate instruments. That is, -First measurement taken using equipment 'A'...
  27. T

    Magnetic Field measurements: Weird FFT signals I cannot explain.

    Hi all! First off: I don't know which forum to post this. I'm no grad student or PHD so academic forum seemed wrong, and it's not really just math, since it was the result of a measurment and the signals can come from environment, etc. Ok. I measured the magnetic field using a sensor...
  28. R

    Maximum precision of deterministic measurements

    Okay, I tend to have some weird thoughts, so bear with my odd question here. Suppose you have a collection of particles that obey Newtonian mechanics. For simplification, all particles are identical and can be assumed to be hard spheres that collide elastically. Each particle has a position...
  29. A

    How are measurements done in the Doppler Orbitography Radiopositioning

    How are measurements done in the Doppler Orbitography Radiopositioning integrated by satellite.Please tell in detail.Or books related to it.
  30. I

    Electric field measurements inside a conductor

    Hi we all know that electric field inside a conductor is zero in electrostatic case. but this is macroscopic field which is averaged over time and space coordinates. what about the instantaneous electric field inside the conductor. are there any experiments done to measure this...
  31. B

    Determining the Radius of the Moon (Ratio and shadow measurements)

    Hello. I have been going through some old OU books on the sciences and started working through an excercise when I came to a stumbling block. I have come here in the hope that someone may be able to shed some light on my problem. This is all for personal study as I am not enrolled on any...
  32. K

    Accuracy and confidence intervals onf measurements

    Dear all, I have a specification from a tool, which says, 80% of the reported measurements are within plus or minus 10% of the actual, at 95% confidence level. I am trying to make sense out of this statement. Assuming a normal distribution, please can someone tell me how to interpret...
  33. R

    A question regarding the B-V measurements of stars

    I've been looking up some information regarding the Owl Nebula, in order to make some calculations of my own. I've only been able to find the V magnitude or the general magnitude of the nebula as a whole. Is there any way to find the B magnitude or the B-V measurement of the star, given what...
  34. StevieTNZ

    What are the four bell states and how do they relate to entanglement swapping?

    In entanglement swapping: If we detect photons 2 and 3 in the following states |135>|45> or |45>|135> (accompanied by the appropriate coincidence counts), do we project photons 1 and 4 into the same bell-state (so photons 1 and 4 are also found in either |135>|45> or |45>|135>)? How would...
  35. D

    Measurements of the second kind and unitary treatment

    I'm struggling to figure out whether measurements of the second kind can be treated using the unitary ansatz. as far as I can gather Von Neumann's measurements of the first kind can be modeled as below: for system being measured S and apparatus A with states |S1>, |S2> and |A1>, |A2>...
  36. S

    Hall Effect Current Sensor Measurement Fluctuations at low current measurements

    Hi, I was trying to measure DC link current on a switched mode power supply when I came across a quirk of my circuit. I'm using an LEM HX 03-p SP2 hall effect current transducer to measure current. I couple the output node of my current transducer to ground via a 2KΩ resistor. The device's...
  37. N

    How Do You Convert Proton Flux from 1/(cm^2 s sr) to 1/(cm^2 s)?

    Dear forum users, I have a quite simple question. I have got a flux of protons measured in 1/(cm^2 s sr), I would like to have it in 1/(cm^2 s). nykon
  38. G

    Wing bending measurements while in level turning flight

    Hello everyone. I wanted to know if, for low wing single engine nose-driven prop aircrafts, there has ever been a measurement done, while in flight, of the actual amount of wing bending occurring during sustained level turns at a measured G force, including full power sustained turns...
  39. andrewkirk

    Can making a measurement change subsequent measurements?

    Consider an experiment in which a closed box is set up with a system inside that is initialised at time t=0 with state psi(0). A measurement of quantity w of the box’s contents is made at time T, that is observed by scientist S1. There is another scientist S2 that can, by pressing a button...
  40. F

    A fair way to measure the difference of two measurements

    I would like to ask if anybody can help me figure out a fair way to measure the difference of two measurements in percentage. I have two sets of measurements X and Y, and both are data with unknown noise. To measure the difference in percentage of these two, both equations can be used (I...
  41. D

    How stirring a liquid affects temperature measurements.

    Homework Statement "Some people say stirring a hot liquid with a thermometer gives a better measurement and some say it yields a worse measurement. Explain with physics how one is actually better" Homework Equations None that I know of. The Attempt at a Solution I know that...
  42. T

    Calculate the height of a building using scale measurements

    Homework Statement Supposedly, I put an object on a scale inside the elevator of a building, the scale reads m1. I start the elevator to the top of the building, during acceleration, the scale reads m2. As the elevator normalized, the scale reads m1. During the deceleration at the top, the...
  43. T

    Effect of the Galactic plane on the COBE CMBR measurements

    http://cosmos.lbl.gov/two_four_maps.html http://cosmos.lbl.gov/Images/phys_today_cover_big.gif CMBR dipole anisotropyFrom the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627±22 km/s...
  44. D

    Speed of light measurements using different light source.

    As far as I know all light speed measurements done using light sources that utilized electrons. The nominal light speed measurement used laser which is actually exited electrons. The speed of X-ray radiation from synchrotron used accelerated electrons. The speed of gamma radiation also involved...
  45. R

    Termal measurements in a closed chamber

    Hi! I'm having problem with measuring the temperature in a closed (vacuum) chamber. I'm using thermocouples (type T) connected to the object inside the chamber, but both the copper wire and the konstantan wire are then connected to copper wires before exiting the chamber. Therefore I cannot set...
  46. 1

    Ancient Engineering Measurements

    Not sure where this one should go, please move if this is the wrong forum: There is a verse in the Christian Bible where a bowl is described to have the following dimensions: 10 cubit diameter 30 cubit circumference 1 Handsbreadth thickness A modern cubit is 18 inches, 1...
  47. A

    Measurements - relation between mass and size

    Homework Statement Why are mammals as large as they are and not much larger? Homework Equations Two figures are given. One of the mammal with size S and mass M. Femur is the thigh bone of the mammal with l being the length of the femur, d being the thickness of the femur and A being the...
  48. W

    Unit analysis - using measurements as variables - correct (?)

    Homework Statement Currently, I'm expected to find the side length of a square garden whose area is 25cm2. Of course, we're talking about a square here, and since the area of a rectangle is l * w, and, when talking about a square, l = w, the area of a square is S2. Of course, I know each side...
  49. S

    Basic measurements and conversion not so basic

    Homework Statement During heavy rain, a section of a mountainside measuring 3.6 km horizontally, 0.53 km up along the slope, and 1.1 m deep slips into a valley in a mud slide. Assume that the mud ends up uniformly distributed over a surface area of the valley measuring 1.2 km x 1.2 km and that...
  50. LarryS

    Are Coherent Superposition Particles Considered Conservative Systems?

    Say we have a stream of particles, emitted from a source, traveling freely in one direction and then colliding with some sort of screen. Between the source and the screen the particles are said to be in that indefinite state of limbo known as coherent superposition. Do the particles in this...
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