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

    Quantum Zeno effect for position measurement

    Hello, The quantum zeno effect is well understood and experimentally confirmed as regards polarization measurements (as discussed here). It's the quantum analogue of "the watched pot never boils" as it allows "continuous" measurement to inhibit certain state evolutions. Does the effect...
  2. coktail

    Uncertainty Principal: Limit of measurement, or the nature of things

    Hi! I found a few old threads lying around regarding this, such as this one, but I thought I'd start a new one asking the question in my own way. So here goes. Is the uncertainty described by the Uncertainty Principal a result of the fact that by measuring something we affect it, or a...
  3. M

    Relation between actual measurement and Mathematical observables

    I'm having a gap in understanding the relation between them, and resolving my confusion is really appreciated. For example, the Hamiltonian operator, why do we call its eigenvalues energies? how do we actually measure it in the laboratory, quantum mechanically? And maybe I need a better...
  4. G

    Time 'measurement' (or definition) for early universe

    We define time by the rate at which physical processes (i.e. clocks) tick. With atoms for example we can define time by their energy transition rates such as in atomic clocks. But, what before atoms existed? Current cosmology theories make statements such as that '0.5 seconds after the Big...
  5. M

    Wavefunction after position measurement

    Suppose I have a particle confined between 0 and d on the x axis, and it has some wavefunction, if I measured the particle to be between some small interval [a, b], would the wavefunction collapse into a rectangle-like function with equal prob. density on the interval and zero outside? or what...
  6. S

    C: Modelling errors in a measurement

    Homework Statement I'm currently writing a program that will read in a list of gaussian distributed random numbers as an array and will make a 'measurement', that is they will be assigned to another array with an associated error. This is to try and simulate the communication of Alice to Bob...
  7. M

    Voltmeter relative error question. (Computer Controlled Measurement)

    Homework Statement You measure 50V with a voltmeter, which has 300V as the max. input voltage. What will be the relative error (h%) of the measurement? Homework Equations The Attempt at a Solution hi i divided 50v / 300 V and get = 1,66 and divided it by 100 to get relative error...
  8. P

    Confirming Faraday's Law - interference in measurement.

    Hi, Homework Statement We ran an experiment for confirming the linearity of Faraday's Law (the relation between EMF and the rate of change of flux), by plugging a magnet to a motor rotating in the axis of a solenoid (inductor). In my graph of the amplitude of EMF wrt time, I noticed some...
  9. R

    The proportion of Hydrogen to limit errors in measurement.

    It is proposed to use a katharometer to mesaure the amount (about 5%) of oxygen in nitrogen, in the presence of a small amount (0.5%) hydrogen. How constant would the proportion of hydrogen have to be in order to limit errors in measurement of % oxygen to +/- 0.1%? The thermal conductivities...
  10. M

    MHB Visualizing Data, Significance Level, T-test, Level of Measurement

    Hello. I was just wandering if anyone could help. I've been doing a couple of statistics questions, and when they ask for some questions, I am not sure if I have an appropriate understanding of what the right answer should be. I would really like to understand this material, so what I want to...
  11. L

    The uncertainty principle and the measurement postulate

    Hi everybody. I have a quick question regarding the relationship between the uncertainty principle and the measurement postulate. According to the former, the higher our certainty is about the position of a particle, the lower our certainty is regarding its momentum, and vice versa. This...
  12. DrChinese

    Double-slit interference pattern measurement with entangled photons

    Although it is well known that a series of individual photons will build up an interference pattern in a double slit setup, there have been few (if any) experiments where such a pattern is built up by sending photons through one at a time. Here is a great experiment from one of the top quantum...
  13. B

    Scale Design Using an Angle Measurement for Weight

    Homework Statement I have to design a scale to weigh something under 1kg and all am given is a yard stick, 10 ft of fishing line, a 500g known standard mass, and a protractor. Use an angle measurement for weight. Don't just balance weights on a see-saw Homework Equations - The...
  14. A

    Measurement of Galvanic Skin Response

    Homework Statement I have attached the photo of the circuit. My doubt in the circuit is that, I could not exactly figure out what the diodes do. The description says it is used to set the input of the op-amp to 1.6V above v-. But how exactly does it achieve that? Can somebody show it...
  15. V

    General Entanglement and Measurement

    I apologize in advance if this has been asked many before, but I didn't see anything that answered my question on the first page of threads. Take, for example, an isolated subatomic particle which breaks down into two entangled particles. From what I've read, each of these two particles...
  16. shounakbhatta

    Uncertainity regarding measurement

    Hello, I was viewing a lecture of one of the professor's most possibly in MIT who demonstrated in the class room, by calling a boy and measuring him, while standing, a certain measurement say 5 ft. After that he asked the boy to lie down and again measured him and found that there is a...
  17. bhobba

    Interesting View Of Quantum Mechanics and The Measurement Problem

    I have been going through the following interesting paper on the foundations of Quantum Mechanics: http://arxiv.org/pdf/0911.0695v1.pdf 'We define the state of a system as that mathematical object from which one can determine the probability for any conceivable measurement. Physical theories can...
  18. Astronuc

    Radiation Detection and Measurement, 4th Ed by Glenn F. Knoll

    Author: Glenn F. Knoll Title: Radiation Detection and Measurement Amazon Link: https://www.amazon.com/dp/0470131489/?tag=pfamazon01-20 Prerequisities: Sophomore (2nd year uni) level courses in modern physics and EM, mathematics through differential equations, Level: Undergraduate...
  19. S

    Does Conscious Observation Influence Quantum State Collapse?

    Do you believe that "conscious" observation has anything to do with "collapsing" superimposed quantum states, or do you simply believe that interaction with a macroscopic, or sufficiently large system, is what causes superimposed quantum states to collapse? Why?
  20. A

    Measuring AC Voltage from 60V-300V with Microcontroller

    I want to measure ac voltage raging from 60v to 300v using microcontroller i have figured everything else out except how can i use 220v transformer(to step down the voltage to measure) when input is 300v one solution is to use simple resistors based potential divider to attenuate 300v to 220v...
  21. Demon117

    Calculating the probability of a certain measurement

    Homework Statement This really is not a homework problem but I am studying for the qualifying exam upcoming. I came across an objective that I am not familiar with. I'm given a wave function made of a linear combination of spherical harmonics with complex coefficients. I'm asked to...
  22. C

    Spin-1 Particles Results of a Measurement

    Homework Statement Spin-1 Particles prepared in the state: $$ |\psi> = \frac{2}{\sqrt29} |1> + \frac{i 3}{\sqrt29}|0> - \frac{4}{\sqrt29} |-1> $$ Where I'm guessing the ## |#> ## represents the spin state of -1,0 or 1. I'm looking to find the results of a measurements of the ## S_x ##...
  23. S

    Vapor Pressure Measurement Problem

    Hi all, Just have a quick question regarding the measurement of vapor pressure. Firstly, let me explain my scenario. I am carrying-out some measurements of steam condensation in a vacuum. The steam is being condensed in a air-cooled heat exchanger. Initially, I let in a quantity of steam...
  24. P

    Accurate phase measurement with relativly low sampling frequency

    Hello. To give some more information on what I am to use this for: I have two signals. Both are periodic sine waves with the same frequency, but with a constant phase difference. Let's call one of the signals for ref (reference) and the other sig (signal). They can look like this: ref(t)...
  25. S

    Pressure measurement in U tube with mercury and water

    Homework Statement Mercury is poured into a U tube. The left arm of the tube has a cross sectional area A_1 of 10 cm^2 and the right arm has a cross sectional area A_2 of 5 cm^2. One hundred grams of water are then poured into the right arm of the tube. A: Determine the length of the...
  26. bcrowell

    Physical model of measurement for affine geometry, dual

    We recently had a long thread https://www.physicsforums.com/showthread.php?t=666861 about cases where raising and lowering indices isn't completely natural, i.e., where a vector "naturally" wants to be upper-index or lower-index. If you have a metric, then it's pretty clear to me what...
  27. M

    HUB & accurate single measurement

    Hello, I recently read some texts which says that in a SINGLE measurement you can measure position and momentum to an arbitrary accuracy, assuring that that's not what HUB talks about. That confuses me, because I learned that HUB is there NOT simply because some property of QM prevents us...
  28. J

    Unit of Four Dimensional Space Measurement?

    I have been wondering what type of measurement is used to measure the space inside of a four dimensional (space, not time) object. For example, a one dimensional line's distance gets measured, a two dimensional object's area gets measured, and a three dimensional object's volume gets measured...
  29. N

    Light Years: Subjectivity and Distance Measurement

    Light years-I just don't understand how something as subjective as visibilty, is used as a major indicator of distance. Isnt that subjective. What if some species had a million times the eye power than us humans, wouldn't they view the distance of let's say stars very differently because it...
  30. M

    Force measurement system - relating output voltage to Force - strain gauges

    Homework Statement I'm struggling with this, I have series of data for the deflection of a cantilever beam and the corresponding output voltages from a strain gauge, wheatstone bridge and amplifier circuit. I'm trying to find the relation between voltage output and force, i.e. Force = K x...
  31. C

    Direct Measurement of Gravitational Wave Velocity

    http://www.spacedaily.com/reports/Chinese_scientists_find_evidence_for_speed_of_gravity_999.html Done by the Institute of Geophysics at the Chinese Academy of Sciences using Earth tide measurements. The conclusion is that it is the speed of light. http://en.wikipedia.org/wiki/Earth_tide...
  32. C

    Why is Carbon-12 used as the measurement of relative masses?

    Hi everyone, This is really annoying me, so, I am aware of the story why oxygen was replaced with carbon-12, (because chemists were using natural occurring oxygen which was a mix of oxygen-16,17,18 and therefor was an avg?, but physicists wanted pure, isolated oxygen-16 so there was two...
  33. S

    Mach-Woodward Effect: New Experimental Measurement Setup Proposed

    Professor of Physics History at CalTech, Dr James Woodward has been investigating an idea called the Mach Effect, which is supposed to be based on Mach's Principle and which is claimed to allow a means for propellantless propulsion without violating Conservation of Momentum. The idea is that...
  34. Z

    Magnetic field measurement with high accuracy

    Hi, I would like to use a Hall Sensor (e.g. http://fwbell.com/Category/2.aspx) or a Hall Element IC, like the AD22151 device for magnetic field measurement with a range from 0 to ca. 0,5 mT with a resolution of 250 nT. (500 ppm) The temperature fluctuations are max 1 C. Do you think I can...
  35. K

    Measure Magnetic Field Frequency - Handheld Meters

    Does anyone know how to measure the frequency of a magnetic field? They sell handheld meters but they only measure Mhz and higher
  36. M

    Spectral transmittance measurement

    Dear all, I am new in this forum; from a first sight I realized that you can help me to clarify a doubt. My experiment requires the measurement of spectral trasmittance of a simple by using a white light source (400-800 nm) and a silicon photodiode. I know that a proper measurement require to...
  37. D

    Measurement of concentration of urea

    Dear All Does anyone have any idea about how to determine the concentration of liquid urea. The concentration is a bit higher (0.5-1.5 mol/L). Is there any laboratory techniques or Kit? I looked for and found everywhere the method to measure the amount of urea in blood and urea but what I want...
  38. M

    Understanding Eigenvalue Measurement in Quantum Systems

    when we have a certain state ψ(t) and it is acted on by an operator A of eigenstates a, b, c and eigen vectors la>, lb>, lc> does it mean that after measuring A ( if the result was 'a'), the state lψ(t)> becomes in state la>?
  39. P

    Does Decoherence Solve the Measurement Problem Completely

    As the Title describes, Is the measuremet problem completely solved by the decoherence Program? In specific I would like the following question addressed. Is there is clear explanation as to what it means to Record Infromation? Can it explain the behaviour of a photographic plate? What happens...
  40. D

    What is Order of Magnitude and Significant figures in any measurement?

    In any physical measurement we often refer to two terms... 1.'Order of Magnitude' of certain quantity 2.the number of 'Significant figures' What they actually mean?
  41. Mordred

    Simultaneous measurement article

    came across this article thought everyone here would be interested in it http://www.sciencedaily.com/releases/2012/11/121101141107.htm essentially they are measuring the particle and wave properties at the same time of photons.
  42. O

    General/special relativity-a measurement problem

    [b]1. The problem statement: all variables and given/known Describe a Non-Local Expirement that will lead to the conclusion that a body is in fact in a revolving system and not a system of constant acceleration. Non-Local meaning that the expirement uses 2 measurement instruments at 2...
  43. C

    Methods of Accurate Dynamic Mass Measurement?

    Hi all, As part of a project I am working on, I need a method of dynamically measuring change in mass (preferably at least 1 measurement per second). The maximum expected load is 10kg, and the measurement needs to be accurate to at least ±0.1g. So far, all that has been suggested to me is the...
  44. F

    Impedance analyzer, three terminal impedance measurement

    Homework Statement 5. What is measurement technique in impedance analyzers? 6. Draw the circuit of a two terminal impedance measurement. 7. Draw the circuit of a three terminal impedance measurement. 8. Draw the circuit of a four terminal impedance measurement. 9. How can you calculate...
  45. M

    Measurement Devices: Tachometers

    Hello All, I am experimenting with DC motors and different speed settings, and I am looking for a way to measure RPM at different voltages and loads. I have been looking at different tachometers and trying to determine what my best option is. The reading does not have to be super sensitive...
  46. D

    Gravitational Constant Measurement ?

    How did we measure the gravitational constant G = 2.034 x 10 ^ 17 cm ^ 2 and the Earth average density (specific gravity) p = 3.45 g / cm ^ 2 s ^ 2.
  47. S

    Probability that a measurement of Sx will yield hbar for this state

    Homework Statement Alright, so there is a problem in the Townsend quantum mechanics book that reads: What is the probability that a measurement of Sx will yield the value hbar for this state: The state is given by: |ψ> = 1/sqrt(14) * (1,2,3i) (But the vector is represented as a...
  48. O

    QM: measurement vs interaction

    I'm just wondering... Regarding the single & double slit experiments... Why does every interpretation say that the photographic screen is 'measuring' the position of the particle traveling towards it? Why not say that the photographic screen interacts with an electron that is spread out...
  49. G

    What is the range of angles for the quantum spin correlation formula?

    So in my quantum class we learned that if you measure spin in one direction and get h/2 and then in another direction that it will be (plus or minus)h/2 as well. I was wondering how you would know the probability of it being the positive value vs the negative value. It's a function of the...
  50. R

    Can EPROMs Be Effective UV Light Detectors?

    Using an EPROM as a UV detector. I was planning to make a UV meter using an EPROM. The idea was that ultraviolet light erases an EPROM. When a fully programmed EPROM (all zero's) is exposed to uv light I should clearly see the number of bits (one's) increasing. So I have built a small...
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