What is Measuring: 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. A

    I Measuring electron spin and measuring entangled electron spin

    Hi people, Lets assume, we have a stern gerlach setup and we are going to measure an atom's last orbit electron's spin with 60 degree from vertical axis. Therefore, in this case, our outcomes would be 3/4 for spin up, 1/4 for spin down. Let's assume, we have the same setup but we are going to...
  2. K

    Measuring the Speed of Sound in Water, Using Faraday's Law

    Hi! This project involves both mechanical and electrical elements, so I'm discussing it in this forum since I'm not sure which one it would fit better into. I'm working on an experiment in which I'm trying to measure the speed of sound through water. The approach is simple: I have a long...
  3. P

    I Measuring Low Resistance: Why Meter Bridge is the Preferred Choice

    Why meter bridge is chosen over post office box to measure low resistance?
  4. Al-Layth

    I Measuring the Velocities of Astronomical Objects in the Milky Way

    I am looking for the most relied upon studies that measured the motions of the sun, earth, jupiter...etc any or all of the various astronomical objects in the milky way galaxy. Particularly interested in the orbital velocities of the planets
  5. abdulbadii

    Measuring thermal conductivity of a metal

    What'd be practical method and/or portable, simple tool (like sort of electricians' multimeter) to meter the heat conductive constant of a metal?
  6. H

    Probabilities of measuring ##\pm \hbar/2## along ##\hat{n}##?

    Hi, Given a spin in the state ##|z + \rangle##, i.e., pointing up along the z-axis what are the probabilities of measuring ##\pm \hbar/2## along ##\hat{n}##? My problem is that I'm not sure to understand the statement. It seems like I have to find the probabilities of measuring an eigenvalue...
  7. S

    Engineering Measuring rotational speed for Tachometer vs Oscilloscope

    Question: Why does the oscilloscope double almost the exact value of rotational speed measured by Tachometer? Rotational speed from Tachometer = 1930 [RPM] Frequency of 1 period = 64.3 [Hz] which means 3857.91 [RPM] The output waveform of hall-effect sensor is attached. Can you have any...
  8. C

    Measuring wavelength of microwave radiation using double slits

    For this problem, The solution is, However, when they found the angle, they did not account for the uncertainty. I guess this is allowed still since the sine of the angle will still be greater than 1, correct? Many thanks!
  9. C

    I Ways of measuring open quantum systems

    At the heart of the theory of open quantum systems is the idea that the measurement statistics of many-body systems can be expressed in terms of a reduced density matrix, obtained by tracing over degrees of freedom that are irrelevant to the system of interest. In general, given a pure state...
  10. Richard90

    Finding an Equation for Measuring Reactive Force at the Gastrocnemius

    Good morning, I’m new to the forum, thank you in advance. I’m an Italian med student based in France. I’m struggling to find an equation for a project that I am following. I should measure the reactive force at the level of the gastrocnemius (shown in the figure, red arrow). I know the force...
  11. L

    I Measuring Model Rocket Velocity: Is it Possible?

    Question, if i record a video of a model rocket launching, and then falling, is it possible to get the actual (or extremely close) velocity every 1 second? thanks
  12. A

    I Measuring the rotation curve of galaxies

    What should I learn to make astrophysical measurements from open data? Suppose I want to measure the rotation speed of galaxies to generate galactic rotation curves like these: https://en.wikipedia.org/wiki/Galaxy_rotation_curve What should I do and what should I learn? I think I should get...
  13. Hereweald

    B Curious about this proposition for measuring for FTL

    So the theory relates to measuring yhe state of a quantum particle, say up or down. Specifically this build on the technique described as repeat measurements seen in this video: I understand why repeat measurements wouldn't work. However what if this series of measurements was done multiple...
  14. String theory guy

    Why Measure the Center of Mass from the Same Position After a Collision?

    For example, in the problem below, if the center of mass is chosen to be measured initially at the center of the left mass, then it must be measured from the same position after the collision. This gives an initial COM of, and finial COM of, Which gives their change in center of mass of...
  15. earthling75

    Stuck calculating probability of measuring ##S_y## for spin 1 particle

    I know how to construct Sy for spin = 1 case from the raising and lowering operators. I get $$ S_y=\frac{i\hbar}{\sqrt{2}}\begin{pmatrix} 0 & -1 & 0 \\ 1 & 0 & -1 \\ 0 & 1 & 0 \\ \end{pmatrix} $$ From what I have seen, the eigenspinor for $\hbar$ is found by solving $$...
  16. B

    A Quantum projection when measuring state population

    Hello! I have two energy levels of opposite parity close by (we can assume they are far from all the other levels in the system) and an off-diagonal term in the 2x2 matrix Hamiltonian that weakly couples them. I initially populate only one parity state, say the positive one, and after a while...
  17. A

    RC Circuits: Measuring Capacitance

    I thought that if the slope of the T versus R graph is 4.00μF, then the capacitance would be 4.00μF but it says that's wrong. I know I'm doing something wrong but I'm not sure how to approach this problem. Can someone help?
  18. squeekymouse

    B How to understand the steradians equation for measuring a sphere of light?

    Hello and please know I am very greatful for your help! I am wanting to learn how to measure light. I have chosen a specific light for this to help me better understand. Lm- 7800 CD-620.7 So, I got that far, lol. I don't really know how to input the numbers for the Steradians equation, I have an...
  19. kma

    How accurate is a multimeter when measuring current

    Hi. I want to ask a quick question, how accurate are multimeters? Like is every current detected on a multimeter a legitimate current or can it sometimes detect false currents, and can it miss any currents that are there? And how accurate are the values on there when it comes to what the current...
  20. Talal

    Measuring the critical capillary number

    Is there a way to measure the critical capillary number? I am running water flooding tests in micro single capillary ducts. I am displacing oil in my experiment, and my channel should be oil wet. I was able to measure the properties of both fluids, this includes; Kin and Dyn Viscosities...
  21. K

    Measuring Pressure on a Concrete Table

    Hi guys, I am not doing homework, it is just suddenly brainstormed this question. What if I place a very small mass like 10kg on the center of a concrete 10m*10m flat table supported by the ground, then how to measure the surface pressure acting on the center and right on the edge? Or the...
  22. Wrichik Basu

    What is the correct way of measuring remaining battery capacity?

    I was searching for a way to measure the remaining charge of a battery using Arduino. Most (almost all) of the tutorials are simply measuring the battery voltage using the ADC on the Arduino. The calculations are pretty straightforward after that — ##5 V## is mapped to ##1023## and ##0## is...
  23. Astronuc

    Measuring Earth and its Mountains

    Earlier this year PBS NOVA broadcast a documentary on measuring mountains. It covered Everest (Nepali: सगरमाथा, romanized: Sagarmāthā; Tibetan: Chomolungma ཇོ་མོ་གླང་མ) and K2. The history behind measuring mountains and the elevations of Earth's surface is fascinating. The old way involved...
  24. flying_bear

    I Lux-meter, candelas or lux, measuring nits in practice

    My lux-meter can be used in two modes, candela and lux. How do I use it to accurately measure a display's luminance in nits? The screen isn't Lambertian, I have to assume this as an unknown. I'm interested in the luminance as seen by the eye looking at the screen perpendicular to it. Now, first...
  25. Mayan Fung

    I Measuring the built-in potential of a pn junction

    I am thinking about the reason why we cannot probe the built-in potential across a diode with a voltmeter. Obviously, a diode is not an energy source, so it is impossible for it to show a voltage reading. After doing some research, I found some explanations and some questions about them. 1. The...
  26. PhysicsTest

    Measuring Phase to Phase voltage using Multimeter

    I want to understand the concept of measuring the phase to phase voltage using multi meter. For example if i want to measure R-Y voltage, i connect the positive probe of the multi meter to the R phase and the negative probe to the Y phase. But both phases will be sinusoidal, so how does it...
  27. E

    I Measuring Spacing with Shortcut Technique: Is Uniformity Achieved?

    I saw on a home improvement show some "shortcut" for measuring out a series of fixed measurements over a distance (it pertained to spacing baluster for porch railing). The contractor places a series of lines of some small incremental distance (1 or 2 inches say) on an elastic fabric band, and...
  28. N

    A Measuring the Wigner Function

    Suppose i measure the phase and amplitude of some radiation, this might be a coherent state of an entangled state, how would i construct the Wigner function from these measurements?
  29. TheSpectacularSpecs

    I Surface Differential Rotation by measuring the position of sunspots

    I am doing a University lab project where I measure positions of sunspots (using images from NASA's SDO) and use them to calculate the rotation of the Sun. Currently, all is going well: I have the angular velocity of several sunspots at varying heights. However, I want to be able to find the...
  30. Yan Campo

    I Probability when measuring a local observable

    I have information that $$\rho_{ab}=\sum_{j}p_{j}\ket{\Psi_{j}^{ab}}\bra{\Psi_{j}^{ab}}$$ and $$Pr(o_{j}^{(a)}|\Psi_{ab})=Tr_{ab}(\ket{\Psi_{ab}}\bra{\Psi_{ab}}(\ket{o_{j}^{(a)}}\bra{o_{j}^{(a)}}\otimes \mathbb{I}_{2})) \text{.}$$ I started by representing the density operator for pure states...
  31. N

    Medical Error measuring glucose optical sensor

    Hello We have designed an optical sensor to measure glucose. But we do not have the same changes for different concentrations. What do we need to do to be able to observe different Lifetime concentrations? In our sensor test, we used phosphorescence and glucose oxidase technology. The sensor...
  32. iochoa2016

    I Measuring characteristic impedance as suggested by KRAUS' book

    Can someone provide more information about this method to measure chracteristic impedance using resistance paper?. Kraus' book claims that the characteristic impedance can be measured by simple dc measurement. It even shows a case to mesure the impedance of a coaxial cable with square outer...
  33. J

    Measuring particle mass in eV

    not technically a homework question, just figured it fit here.
  34. mastermechanic

    Measuring the total pressure of a centrifugal compressor

    Hello everyone, Nowadays I am planning to redesign my centrifugal compressor which I designed for a subsystem in my graduation project. It's a 3D printed and brushless motor driven centrifugal compressor and its about a hand size. However, due to its relatively small size and relatively low RPM...
  35. alan123hk

    B Measuring Light's Brightness & Power Flux Relative to Observer's Speed

    Assuming that the observer moves along the direction of the light, does the speed of the observer's measuring instrument relative to the light source (which may be close to the speed of light) affect the brightness and/or power flux density measured by the observer? I'm not sure about this...
  36. ARoyC

    Measuring Capacitance using a basic Multimeter

    Is there any way to measure the capacitance of a capacitor indirectly using a multimeter that does not have the option to measure capacitance directly?
  37. C

    I What is this formula measuring error?

    Variance and standard deviation and other measures of error I understand. This formula doesn't behave well for data sets centered around zero and also has other problems, like scaling differently as N increases than the standard deviation or standard error. Does anyone recognize this and can...
  38. C

    B Measuring change in g with height (TV program many years ago)

    Bit of a long shot but can anyone remember a TV program where the presenter measured the weight of something at ground level and compared it to the weight at the top of a tall building, possibly the Empire State building? Sorry I can't recall more details. Think it was at least 10 years ago...
  39. B

    A Measuring new forces with molecular vibrations

    Hello! I noticed in several papers describing high resolution vibrational measurements in diatomic molecules, such as this one, in the conclusion section, that they mention that we can search for new forces (or deviation from gravity inverse square law) between the 2 nuclei by measuring well...
  40. T

    Measuring time constant using an inductor with a core vs. no core

    I'm doing a simple RL Circuit Lab where students use 800- and 1600-turn air core coils to measure the time constant. Experimental results very nicely agree with predicted results. However, when students insert a steel (or iron) core in the coils, experimental results are far different than...
  41. Sciencemaster

    I Exploring Wave Function Collapse and Measuring Particles

    Hello! Let's say we have a wave function. Maybe it's in a potential well, maybe not, I think it's arbitrary here. This wave function is one-dimensional for now to keep things simple. Then, we use a device, maybe a photon emitter and detector system where the photon crosses paths with the wave...
  42. kimiko333

    Measuring the length of a moving Beam in two different directions

    v_g+v_e=15/t_1 v_g-v_e=10/t_2 v_g=s/(t_1-t_2) But there are too many unknowns. What am I missing?
  43. Ebi Rogha

    I Measuring Photon Intrinsic Nature: Is Interference a Factor?

    I would like to know, how can we be sure this is not due to the influence/impact/interference of our measurement, not necessarily the intrinsic nature of photons? In most reference books, it seems it is a given and it is not discussed
  44. sophiecentaur

    Measuring your body volume without getting wet

    Air displacement plethysmography I saw a tv programme many years ago which shows this method of measuring the volume of a patient's body. Air displacement plethysmography was a procedure that I saw being used and, tbh, I never asked myself how it works, until now. It's smart, imo. You put...
  45. MikeandSuch

    Measuring the speed of light in a straight line

    So recently I watched a video detailing how it is impossible to measure the speed of light in a straight line because it's not possible to synchronize two-time measuring devices without first knowing the speed of light. But I was thinking if light can orbit a black hole in the photon sphere...
  46. Marioweee

    Probability of measuring an eigenstate of the operator L ^ 2

    Calculate, with a relevant digit, the probability that the measure of the angular momentum $L ^2$ of a particle whose normalized wave function is \begin{equation} \Psi(r,\theta,\varphi)=sin^2(\theta)e^{-i\varphi}f(r) \end{equation} is strictly greater than ##12(\hbar)^2##...
  47. C

    B Measuring Time: Identifying Slower Clock w/ Two Identical Clocks

    If we have two clocks, A and B, that are identical, and if one is moving with respect to the other one, we know that they must run at different speeds. (Right?) One must run slower than the other. But we cannot tell which of the two clocks is the "moving" clock. So, how do we determine which...
  48. T

    Measuring high velocity airflow

    I have a fan that consumes 60 W and blade diameter is 12 inch. If it's just 60% efficient, then the velocity of air coming out of it is around 9.5 m/s. I also have a nozzle inlet of which fits the fan and the diameter at the throat cum exit is 3.5 inch. I want to know how to measure the velocity...
  49. qnach

    Automotive Measuring wood plate thickness

    I have access to only one side of the plate, i.e. cannot clamp both sides of the plate to measure. Is there any way, perhaps acoustic methods, to measure a plate thickness from only one side?
  50. brainbaby

    Measuring ripple reduction in LTSpice

    Dear friends, I am simulating a capacitance multiplier circuit and an RC filter circuit simultaneously. My aim is to check the reduction in ripples when using a cap multiplier circuit against an RC filter. I am familiar with ltspice but not quite an expert. I am comparing two output waveforms...