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.

View More On Wikipedia.org
Recent contents Top users
  1. T

    Pressure measurement with Manometer

    See Attached... Homework Statement A manometer is used to measure drop across an orifice plate measuring the flow of brine (salt water, s.g. = 1.260). A) If the pressure drop is expected to be approx 1000 Pa, suggest an appropriate fluid. Why? B) If the flow rate is anticipated...
  2. J

    Question if expectation value is considered a measurement?

    Hello, I was just curious about expectation values. One of the postulates of quantum mechanics state: The only possible results of a measurement is an eigenvalue of the operator. Now, is the expectation value considered a measurement, thus considered an eigenvalue? Thanks!
  3. K

    Friction Measurement of Rotating Equipment

    Hello, I have two questions that I have been pondering for some time without arriving at an acceptable explanation. The questions require a little bit of background information: I work on rotating machinery that operate across a range of (relatively slow) speeds, and generally has a...
  4. A

    Calculating measurement uncertainty

    Hi, I've been studying uncertainty in measurement. I'm not sure how to decide if the uncertainty of a given measurement should be ±.01 or ±.02 or ±.03, and so forth. I understand that the number of decimal places in the uncertainty calculation should correspond to the number of decimal places...
  5. P

    Eratosthenes' Measurement of Earth's Circumference

    1. When the sun was directly overhead in syene, why was it not directly overhead in Alexandria The size of Earth was first measured in Egypt by Erathosthenes about 235 BC. He calculated the circumference of Earth in the following way. He knew that the Sun is highest in the sky at noon on June...
  6. A

    Measurement in quantum mechanics

    Homework Statement Given a system initially in a state $$| \psi \rangle = \frac{1}{\sqrt{6}} \left(|1\rangle + 2 |2\rangle + |3\rangle \right)$$ where ##{|n\rangle}_{n=1}^{8} ##form an ON basis. If we perform a measurement of an observable corresponding to an operator...
  7. G

    Grounded vs Ungrounded Thermocouples for Tube-Skin Temperature Measurement

    Hello All, We are experimenting with a flame tube design (quite literally, a flame within a tube). We are looking to get a temperature profile along this tube. So, we will need multiple thermocouples along this tube. I'm wondering whether it will be necessary to go to ungrounded (isolated)...
  8. D

    How long does a moun live during a measurement

    Homework Statement A muon with a kinetic energy of 200 ± 0.05 MeV is produced in a linear accelerator. The rest mass of the muon is 106 MeV/c2. (a) Calculate the speed of the muon (in units of c), (b) Calculate the linear momentum (in units of eV/c), (c) How long does it live during the...
  9. H

    Digital Angle Measurement for Rotating Solar Cells

    I am looking for a digital device that is able to measure the angle of a rotating device. It will be used to align rotating solar cells with the sun. These cells are attached to a flat panel, that is fixed in the center with an axis, so only circular movement is possible. The panel needs to...
  10. I

    Measurement of the Speed of sound

    Hai, I have a material related question. I am working with polymeric materials (Poly carbonate's and PMMA's respectively) which have to be tested for impact resistance (at high velocities). It came to my mind if the impact process could be correlated to a sound based measurement. Now i want...
  11. A

    The erase of quantum states by measurement

    I was reading this article, http://www.nature.com/news/2009/090122/full/news.2009.50.html, and it was talking about how they 'teleported' a Ytterbium ion (Yb+) and mid-way through the article it said that they had to destroy the quantum state of the original Ytterbium ion and they did that by...
  12. M

    What does a Bell measurement mean in quantum teleportation?

    Hi, I have a question regarding quantum teleportation. I understand that Alice starts of with a photon A whose state she wants to teleport. Alice and Bob share an entangled pair of photons, B and C. Then Alice does something called a Bell measurement which entangles A and B and the result...
  13. S

    Indoor air quality measurement

    Hi guys I am assigned to do the indoor air quality measurement in 5 buildings which are 2 academic buildings, one residence, a library and a gym. I have to establish a methodology to measure CO2, temperature, humidity, air movement as well as particulates. I have 2 months time to measure and...
  14. Demystifier

    POVM Measurement Example: Intuitive & Easy-to-Understand

    I need a simple, intuitive, and easy-to-comprehend example of a POVM measurement, which is not a projective measurement. Any suggestions?
  15. Demystifier

    Quantum measurement: first kind vs non-demolition

    Can someone explain to me the difference (if any) between measurement of the first kind and quantum non-demolition measurement? Thanks!
  16. I

    Commutators, propagators, and measurement.

    Hi all, Reading through Peskin and Schroeder, I came across the following statement, with regards to propagators: Could someone explain how the commutator is related to the measurement of the field in this context? Searching online, the only thing that crops up is the usual uncertainty...
  17. S

    I am doing a measurement in a system S with the apparatus A, in an

    I am doing a measurement in a system S with the apparatus A, in an entorn E. If the system is at t0 in Sithe measurement of the apparatus will be, after the decoherence time
  18. R

    How are electron position measurement experiments measured out?

    Im interested in knowing what kind of sensors are used and it's overall execution, thanks.
  19. B

    Electrostatic potential with floating metals:computation and measurement

    Hi all, I am considering the situation illustrated in the schematic below. A surface density of permanent charges σ is embedded into a dielectric (with relative permittivity εr) itself sandwiched between two electrically floating metallic plate. We have also L>>t1 and L>>t2. My first goal is...
  20. P

    Measurement of spin due to the force on a magnet

    Can we measure the spin of a particle by measuring the force on a Magnet? I wish to consider a modified stern gerlach like apparatus where a Magnet of mass M is attached to a spring. Can we measure Spin of the particle by studying the deflection of the magnet? Even if it is possible, I can...
  21. 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'...
  22. G

    Measuring Length, Area & Volume: Classical vs Quantum Physics

    I am talking about length area and volume. As I reason it out in my own mind area (and volume) is based on length and involves 2 random measurements of length that are combined (with multiplication as the device of convention - could any other function be used to work as well and as...
  23. S

    Need switching device that doesn't affect impedance measurement

    Hi all, I have a number of underwater transducers that I want to measure the impedance of by using an impedance analyzer. I'd like to create an automated system that cycles the leads of the impedance analyzer to the various transducers, perhaps using something like a decoder or a number of...
  24. K

    Is it Possible to Build a Device for Measuring Speeds of Arbitrary Objects?

    Hi all. I've been thinking of how one can measure the speed (& indirectly velocity, since we know it's direction of travel) of an object. The object is not necessarily an airplane or an automobile since they've their special devices built for velocity measurement. I was thinking of measuring...
  25. P

    Area Law and accuracy of momentum measurement at plank energies

    The general question that I am interested in, is to obtain the number of bits of information one can infer about the horizon by placing measuing apparatus only in a Region of size D. I Imagine a telescore of diameter D that(or devices of that general nature) The standard Theory says that*...
  26. C

    Charpy impact testing angle measurement suggestions

    I am designing my own Charpy impact testing machine and I am unsure what would be the best as well as relatively simple and affordable method I can use to accurately measure the angle the pendulum travels after it has broke the sample. I would also appreciate any complex and more expensive ideas...
  27. C

    Measurement Scales (Statistics)

    Homework Statement In class we have to determine whether something is nominal, ordinal, interval or ratio and with the last 2 (ratio/interval) you have to state if they are discrete or continuous. Homework Equations n/a The Attempt at a Solution Height of Mt Everst above Sea level=...
  28. K

    Wavefunction After Measurement

    Forgive me for asking such a basic question but say for IDSW1 if we have a wavefunction that is a superposition of the first two energy eigenfunctions so: ψ(x)=(1/√2)*(ψ1+ψ2) then if we measured say E1 we can eliminate the inconsistent part of the wavefunction so the wavefunction collapses to...
  29. M

    Math behind rockwell hardness measurement

    I need to calculate the force of a pin impacting a solid metal. I know the shape of the indenter, the precise shape and depth of the indentation and the mechanical properties of the solid metal including modulus, yield and ultimate strength. The pin is being driven by ultrasonic wave guide so it...
  30. H

    Beam Curvature Measurement with a Capacitive Sensor

    Hi, I am trying to measure the center deflection of a simply supported beam with a capacitive sensor. The beam's surface that is the sensor's target is originally flat. After applying equal forces on the two edges of the beam, its center curves upwards (away from the capacitive sensor) thus...
  31. B

    What is the measurement of a Logarithmic

    I was reading a book and it said the sun was 10^12 Logarithmic. What is the measurement of a Logarithmic?
  32. E

    Understanding 3/8''-24UNF 2B x 1-1/2'' Thread Measurement

    What does the thread note 3/8'' - 24UNF 2B x 1-1/2'' mean? I know that the diameter of the thread is 3/8'', but what's the 1-1/2''? Is that the length of the thread?
  33. C

    Detection of a Quantum Measurement

    Suppose it is known that a photon has diagonal polarisation (e.g. it has just passed through a diagonal slit), then Alice comes along and measures the photon using a horizontal/vertical polarisation basis. So, I believe there is a 50% chance she will get a horizontal result and 50% chance she...
  34. B

    Error Calculation in Multiplication of two measurement points

    Homework Statement Hi All, I have a problem in calculating the thickness of a coating material inside a tube. The tubes inside diameter is measured before and after coating. The coating thickness is calculated by substracting the diameters and dividing by two to get the thickness of the...
  35. L

    TGM units of measurement (note: unfamiliar notation used)

    The units of measurement of the SI (System International) are commonly used around the world ·· they form a coherent system usable for a variety of branches of science. But.. there's another coherent metric system that may be a better fit for many applications in chemistry and physics. The...
  36. M

    Extended Kalman Filter : Measurement Matrix

    Hi, I am currently learning and trying to build an extended kalman filter. However I am not sure how to created the measurement matrix. The measurement matrix H is described using formula 3.6 on page 18 of this document http://www.scribd.com/doc/54702247/UAV-Design My problem is that...
  37. S

    How to define measurement in quantum mechanics

    Homework Statement Define measurement in the Copenhagen interpretation of quantum mechanics. Homework Equations The Attempt at a Solution In the Copenhagen interpretation of quantum mechanics, measurement changes the state of a wavefunction, that is, it collapses the wavefunction...
  38. StevieTNZ

    Polarisation Rotators and Measurement

    When we use polarisation rotators to measure certain polarisations for entangled photons, the photon usually meets a polarised beam splitter after. When we detect in the |H> or |V> basis, does that mean the photon is in |H> or |V>? What has happened to the polarisation we were measuring...
  39. S

    Can One Pressure Sensor Accurately Measure Flow Rate in a Pipe System?

    Hello, I am stuck on a pipe flow measurement problem and I would love if some excellent minds would help me out. I have a robot that sprays paint, and there is a motor pump providing the paint to it. I need to be able to measure the flow rate (velocity) of the paint going through the nozzle...
  40. A

    Accuracy, Precision and Sensitivity for measurement instruments

    My book defines accuracy as the closeness of a measurement to the real/actual value, precision as when a set of values are consistent with each other (i.e. close to each other) and sensitivity as the smallest possible reading of an instrument (i.e. to how many decimal places it can measure)...
  41. V

    One way speed of light measurement proposal

    Hello all, Having read many threads and posts about light, it’s speed c, SR etc, the particular issue of not being able to measure the one way speed of light has always stood out and kept me very interested, so, after pondering about it for a while, I would like to propose an experimental...
  42. P

    Why do we use Radian measurement for Time?

    I had a problem where we had to write out the sinusoidal function for the rotation of a ferris wheel. My teacher said that because the rotation was a function of time (x-axis was time), we had to use radians and not degrees. Could someone explain to me if/why you need to use radian measurement...
  43. 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...
  44. P

    Theorem on projective measurement and 100% distinguishable states

    Hi everybody! I'm studying this paper "Unambiguous discrimination among quantum operations" http://pra.aps.org/abstract/PRA/v73/i4/e042301 and they state that Ok, it's well known, but then I took a review of the notes to my course of quantum information and i found this not proven proposition...
  45. S

    Quantum entanglement and measurement operator

    Homework Statement A system in a state \frac{1}{\sqrt{2}}(\left<\phi\right| + \left<\psi\right|) undergoes an interaction with a second system (which is initially in \left<\alpha\right|) and ands up in an entangled state \frac{1}{\sqrt{2}}\left(\left\langle\phi\right| \otimes...
  46. P

    Measurement of material displacement using recorded material thermal data

    Hello all I am trying to measure material displacement using measured thermal data.7 While the specimen is heated up, I want to measure how much it changes its length at particular points. Is this possible? If you have any further questions or suggestions please do not hesitate to...
  47. D

    Measurement problem query

    In the measurement ansatz below, must the state |O,ready> be orthogonal to |O,reads up> and |O,reads down>]? |+x> |O,ready> =1/(sqrt2)[|+z> + |-z>] |O,ready> (1) ---------→ 1/(sqrt2)[|+z> + |-z>] |O,ready> (2) --------→ 1/(sqrt2)[|+z>|O,reads up> + |-z>|O,reads...
  48. J

    Tennis Court Speed Measurement

    Hi everyone, Can anyone tell me what information I'd need to calculate the maximum and minimum bounce angle of a tennis ball being fired at a tennis court? The ball is being fired at 30 m/s at an angle of 16° and the coefficient of restitution of the tennis ball is 0.759. What other...
  49. K

    Measurement of c using Bradley and 1905 SRT aberration models

    At another thread under Special and General Relativity the following question was asked: "Why isn't stellar aberration considered to be a one way measurement of c? If the angle of aberration (θ-θ0) is -20.5 arc seconds and the Earth's orbital speed is 29.79 Kilometers/second normal to the...
  50. X

    What is the difference between interaction and measurement?

    Hello, as far I understand wavefunction collapse (or decoherence or whatever stops particles from acting as waves) is initiated through something referred to as a measurement. These measurements are thought of as interactions. Now the question I have is, why are some interactions measurements...
Back
Top