What is Measurement: Definition and 1000 Discussions

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. J

    Experimental measurement of Einstein's Field Equations

    Experimental "measurement" of Einstein's Field Equations The question is essentially: What if we took a strictly experimentalist view, and considered a phenomenological model for gravity that is a "generalization" of EFE: R_{\mu \nu} - C_1\ g_{\mu \nu}\,R + C_2\ g_{\mu \nu} \Lambda = C_3\...
  2. M

    Measurement problem in double slit experiment

    In double slit experiment of electron, we see an interference pattern when we don’t know through which slit electron has passed and we don’t see an interference pattern when we know through which slit electron has passed. Now, to identify the slit through which electron has passed, we use...
  3. M

    Quantum mechanical measurement (schrodinger's cat)-

    1. Suppose in Schrodinger cat thought experiment we place a camera inside the chamber which record the events happening inside the chamber. (We are not watching inside the chamber through the camera during the period of experiment. It is just for recording purpose). After one half life of...
  4. M

    Simple thrust measurement stand

    I have a thrust producing engine and I would like to measure the thrust from it as accurately as possible without needing the use of scales, rollers, load cells, etc. Anyway a friend of mine suggested I suspend the engine from four wires so that the wires are vertical when the engine is...
  5. O

    Where Can I Find Plans to Build a Hertz Apparatus for Classroom Demonstrations?

    I would like to find a device to reproduce Hertz's experiment that demonstrated the transmission and reception of EM radiation. The equipment as I recall used a Leydan jar, an inductance coil to boost the voltage, a capacitor with a gap that sparked, and separately a ring with a small (I...
  6. P

    A Quantum Mechanical model of measurement

    Following a short discussion in another thread, I promised to start a new thread for this. I asked myself the question "how would I describe the process of measurement in a fully quantum mechanical way?" and came up with this. 1) A model for the general measuring device The aim is to have a QM...
  7. K

    Why does decoherence not fully solve the measurement problem?

    Why does decoherence not fully solve the measurement problem? I know that must have been discussed here before a lot, maybe someone can me direct to a earlier thread or post that explains it well? I read some QM texts, but they mostly do not discuss decoherence. I know something with...
  8. E

    Energy of Measurement - Quantum Mechanics

    Hi all, Consider a simple harmonic oscillator in the ground state. Measuring its energy yields the ground state energy with 100% probability. Now by measuring its position (thereby changing the wavefunction) and next measuring the energy again, there is now a nonzero probability of finding...
  9. zonde

    Nature of probabilistic measurement

    I have a question regarding probability of quantum measurement. Consider polarized photon beam that is going through polarizer. Let's assume that beam intensity is very low so that we can consider it as separate photons going through polarizer one by one. Now if we consider any single photon...
  10. M

    Force Measurement Histogram: Vertical vs. Horizontal Axis

    I am a little confused about a histogram of force measurements. I was asked for my physics lab to state what the vertical axis and horizontal axis represent for a histogram of force measurements? the physics lab consists of pulling a wooden block with a force sensor to record the tension...
  11. L

    Propagating Measurement Uncertainty into a Linear Regression Model

    I am trying to figure out how to combine uncertainty (in x and y) into the standard error of the best fit line from the linear regression for that dataset. I am plotting units of concentration (x) versus del t/height (y) to get a value for the flux (which is the slope) I understand how...
  12. nomadreid

    Measurement effect upon wave function

    If I understand correctly, a measurement affects the wave function only at the moment of measurement. In other words, if one were able to compare two wave functions, one when there were measurements, and one in which there were no measurements, the only difference would be at the meager set of...
  13. W

    Electric Power measurement Current Transformers and reactive power

    Apparently my modern electronic home electric meter uses a 'current transformer' to measure the current in order to calculate the wattage I am using. My question: is the flux generated in the current transformer also proportional to the reactive part of the current as well as the in-phase...
  14. D

    Is Decoherence the Solution to the Measurement Problem?

    Is decoherence a resolution to the issue of measurement? I have read arguments on both sides.
  15. JK423

    What is a non-orthogonal measurement?

    As the title sais... Can someone explain to me what is a non-orthogonal measurement? I searched the web by i can't find any definition
  16. K

    QM Interpretations and the Measurement Problem

    In order to stop hijacking https://www.physicsforums.com/showthread.php?t=361216", I'll restart a discussion here about the role of background assumptions and the conceptual aspects of scientific theories, in particular how the "measurement problem" fits in with quantum mechanics and its...
  17. A

    Measurement of Young modulus of Copper

    Homework Statement my data as below diameter of copper wire/m 0.025 (mean) Unstretched part = 0.285m mass(m)/KG extension(e)/m 0.1 0 0.2 0 0.3 0 0.4 0.001 0.5 0.001 0.6 0.001 0.7 0.003 0.8...
  18. T

    Dynamic resistance vs temperature measurement for ribbon transducer

    I'm interested in doing an experimental analysis of ribbon transducers to contrast with simulations. This data could be made available to the community to aid in transducer development. A ribbon transducer consists of a rectangular element of metal foil suspended within a magnetic gap and...
  19. P

    Temperature Measurement Using 8051 Microcontroller

    Hi..please help me in designing a temperature measurement device using 8051 microcontroller. some one please help me out...with the circuit diagram please:confused:
  20. W

    Bizzard measurement outcome of Angular Momentum, Why?

    Hi there, I am just a bit confused about the measurement of angular momentum. If we have a state which we know for sure the outcome of the measurement of L(z), the z-component of the angular momentum L, say h. Why is it that all the other components, say L(x) would not reveal itself to have...
  21. Y

    Measuring Gravity with a Zero Mass Device?

    If I had a hypothetical gravity measuring device that had no mass, would it be able to measure the gravity of a planet, that does have mass, as it approached it? Or would it not detect any gravity because the device has no mass? I hope this makes sense...
  22. S

    Small, Lightweight Voltage Measurement Device for PC via USB

    I'm looking for a device I can use to measure analog voltage (up to 25V) and send the data to a PC via USB. Only really need one input, though it wouldn't hurt to have more. My main concern is that it needs to be pretty small and light - any ideas? The few I've seen online are either too...
  23. F

    Calculating actual x-ray flux measurement

    Hi, Hopefully I'm posting this in the correct forum. I'm using Nuclear Associates 07-451 flux detector with a gigaohm input impedance such that the measurement read is logarithmically compressed. The x-ray tube is outputting a constant number of rads. The flux sensor is mounted to the...
  24. D

    How Do You Calculate the Curvature of a Simply Supported Monorail Beam?

    Hi wonder if there is anyone out there who can help me ! Whats the easiest formula for working out the measurement of curveture in a simply supported structural horrizontal monorail beam. Any help most appreciated. - thanks
  25. G

    Measurement collapse as a perturbation?

    Is it possible to describe the measurement process in QM simply as a perturbation to the system (either a small one or a very large one) so that effectively the eigenstates of the Hamiltonian evolve into eigenstates of an additional measuring operator? So at t=0 the Hamiltonian H turns into...
  26. P

    Measure Momentum: Experiments & Eigenstate Detection

    Can anyone give an example of experimient which the momentum of particle is measured in. How to detect eigenstate of momentum if its absolute value is equal 1 in whole space (idealized measurement of momentum should concern all space).
  27. B

    Measuring Time: An Experimental Methodology

    This may seem like a silly question, so I shall offer my apologies in advance. I wish design an empirical experiment to show time. I should be able to use a stopwatch to obtain a time value, say 1 s. In order to show that the value which I have measured is not due to (my) bias, I must...
  28. G

    Probability that Measurement of Spinor Yields Spin-Down State

    Homework Statement Consider the spinor \frac{1}{\sqrt{5}}\left(\begin{array}{cc}2\\1\end{array}\right) . What is the probability that a measurement of \frac{3S_{x}+4S_{y}}{5} yields the value -\frac{\hbar}{2}? Homework Equations...
  29. JK423

    Entangled particles and measurement

    We know that if, for example, two particles are entangled in a state like: |Ψ>=a |0>|0> + b |1>|1>, then measuring an observable on only one of the particles it makes the interference dissapear. But isn't it impossible to measure both particles simultaneously in order to maintain the...
  30. M

    Help with Eratosthenes' Astronomical Measurement!

    Astronomy Help! :( I'm sure that compared to all the other problems posted here, this Astronomy problem is incredibly easy, but I'm TERRIBLE at sciences and mathematics and really need some help. The problem is: "Although the distance to the Sun is obviously much larger than the distance...
  31. Z

    State/wave function after measurement?

    If i already know the wave function then measure an observable what is the new wave function? Is it just the eigenfunction of the observable corresponding to the measured value? And does it stay in this state until something interacts with it?
  32. B

    Uncertainty in Measurement (Question)

    In regards to data analysis, what would it mean if you measured some quantity, say the speed of light for example, and you measured an average value that was 110% of the true value. If your uncertainty in measurement is LESS than 10%, does that mean that something is wrong with your data or...
  33. G

    What is a measurement? (layperson question)

    I know this is a hotly debated subject here, but what is the general scientific consensus (or most popular definiton) on what constitutes a measurement? Secondly, are there theories where the measurement problem becomes an illusion because of anthropomorphic bias? (To put in a crude...
  34. P

    Electromagnetic standing waves measurement

    Do you get electromagnetic standing waves? If so, do the electric and magnetic fields not cancel each other because of their opposite direction in the standing wave? Can such a thing be measured?
  35. C

    Measuring Position of a Quantum Mechanical Particle

    How would one measure the position of a quantum mechanical particle? For example, suppose I am aware that an electron lies in a 1-D box of length L. And maybe I wish to know the position of the particle in that box to a certain level of accuracy. I'm satisfied with knowing the position...
  36. S

    QM: Measurement Operation & Operators Explained

    Like all beginners to QM I'm really confused about the measurement operation. I understand that measurement is simply a dot product with an "operator" and the result is one of the operator's eigenvalues. Now my question is what exactly is an operator? If someone could explain what physical...
  37. M

    Understanding Quantum Measurement: Exploring the Role of Methods vs. Observation

    I just had a question about quantum mechanics that has been muddied somewhat by pop culture's understanding of the quantum world. My question is this: Would it be correct to say that the reason that there is inherent uncertainty in measuring the quantum world is because of the methods of...
  38. W

    Did any scientist did experiment to prove that current measurement changed the past?

    Did any scientist do experiment to prove that current measurement changed the past with time stamps on both current and past events? I mean with clear time stamps showing the the past event happened earlier(as proof from a strick time stamp), and it must not be possible to happen if the...
  39. hagopbul

    Solving the Measurement Problem: Imagine Yourself in a Room

    i tried to explain for some one how we can solve the measurement problem and i went like this imagine your self in a room and in this room you don't have any sense so you can't see hear touch smell or even taste but you have a prob attached to your brain but if you don't do the measure you...
  40. pellman

    What is the definition of a momentum *measurement*?

    Let's say I have made a measurement of some sort of a quantum system. That is, I have some macro/classical devices whose states have numbers associated with them, and their resulting states depend (in some way) on a quantum system. So I arrange the lab-plus-quantum system as desired and note...
  41. W

    What do you think these Weak Measurement, Quantum Uncollapse Tests. Re-write QM?

    What do you think these Weak Measurement, Quantum Uncollapse Tests. Re-write QM?? http://www.scienceagogo.com/news/20080706233709data_trunc_sys.shtml http://www.sciencedaily.com/releases/2008/08/080806140128.htm Are they going to re-write the quantum mechanics?
  42. B

    Piezoelectricity measurement

    Hi all, I am trying to measure the piezoelectricity of a polymer film using a picoammeter. Right now I am trying to figure out the best way to make the connection to the film without sputtering electrodes onto it. I figure copper adhesive tape or silver paste might be the best way to go but...
  43. LeonhardEuler

    How does the Schrödinger equation lead to the QM theory of measurement?

    Hi everyone, I've recently been bugged by a question I can't seem to find a reasonable answer to. It's about an apparent contradiction between how the wave equation is supposed to evolve in time according to the schrodinger equation and the measurement formalism in QM. Suppose I have any...
  44. N

    Air pollutant concentration measurement technique?

    Hi all: I'm working in a air pollutant level sensing system, to measure the common air pollutants and their level. I begun with this some months ago (In fact I've taken the others work's in my hands), and used electrochemical gas sensors for low ppm sensing (Up to 50ppm) and with 0.1ppm...
  45. R

    The measurement of current and voltage

    Homework Statement Two scales on a voltmeter measure voltages up to 20.0 and 30.0V, respectively. The resistance connected in series with the galvanometer is 1680 ohms for the 20.0V scale and 2930 ohms for the 30.0V scale. Determine the coil resistance and the full-scale current of the...
  46. I

    Converting Units: Microvolts to Volts and Picoseconds to Seconds

    Homework Statement Would 85 uV (Micro) be 8.5 x 10^-5 V ? And would 600ps be 6x 10^-10 S ? Ehhh I haven't slept in weeks, I just can't focus. Homework Statement Homework Equations The Attempt at a Solution I used the fact that 1u = 1x 10 ^-6 and then I used 1V/1000000uV x (85 uV) and for...
  47. E

    Accurate Height(above sea level) Measurement Device

    Hi Guys I am new engineering and would appreciate any advice or ideas on this project. I need to measure the height above sea level of a small vehicle that I am building.. My first idea was GPS, but the vehicle is going travel under a thick steel structure, so it will not work. I thought...
  48. B

    Auto/Motor Diy measurement of car efficiency

    It seems to me a typical gasoline car has wastes about 95% of the gasoline energy before any rotating energy gets to the wheels. Here's my reasoning. I once measured my cars efficiency (an old Renault 5). I drove 100 km/h (28m/s) on a flat and level freeway, with no wind, and set the gears...
  49. E

    Fuel Measurement: How PWR Nuclear Plants Calculate Fuel Amount

    How do (PWR) nuclear plants determine how much fuel is left? Do they measure it? I heard they calculate it, but i was wondering if any measurement is done? Thanks.
  50. A

    How to write uncertainities on different measurement

    I need some advice on how to write uncertainities on different measurements. I need this urgently. Thanks:cool:
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