Questions tagged [measurements]
Measurements, instrumentation, calibration and metrology.
276 questions
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Can one build an east-west compass using bismuth?
I am reading Oliver Sacks's memoir Uncle Tungsten, The book is remarkably interesting: he was a keen amateur chemist in his youth, and clearly a polymath.I was struck by this:
"It was fascinating ...
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Is it possible to perform a weight measurement of a 200kg object with 0.1g precision, in the range of 199.5kg to 200kg only?
I want to precisely measure the weight change of a 200kg object in an indoor lab setting. The total weight change from start to end of the experiment is only 0.5kg.
I would ideally need a scale that ...
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How to determine unknown concentration of a surfactant in an aqueous solution?
I want your help in determining surfactant concentration in an aqueous solution. Surfactant is an anionic surfactant, namely Sodium Lauryl Sulfate (SLS). I have a pure SLS water solution whose ...
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Help with Flow Measurement and Connectivity Technologies for Smart Cities Projects
I am involved in a project to install smart water meters in a city, as part of a smart city initiative. I am looking for detailed information on the following areas and would like your help:
Flow ...
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Way to measure volume of hole scanned by 3D laser device and CAD
I'm not a mechanical engineer so please let me know if my question is not clear.
There is a hole generated on a pipe wall as shown in the upper figure. I would like to measure the volume of the hole ...
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Janka hardness of Carbon Fiber
I know that Janka hardness is a measurement used for wood. However since I want to build a guitar made of several materials I got curious whether anyone has ever used the Janka test to determine the ...
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106
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Need very flat surface without breaking the bank
I'm not an engineer but I really need a very flat surface that doesn't cost too much urgently. In trying to realign my guitar neck and suspect that it is slightly twisted too. Since I'm a ...
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Determine reading on gauge that doesn't have enough tick marks
Is there a way to determine what the reading is on this voltage gauge using graphics and math? For example, in a computer program, could I draw a circle and then plot evenly-spaced tick marks (between ...
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Inline thickness measurement by optical transmission (Beer-Lambert law)
I am wondering how effective would be an inline system for thickness measurement of diffuse plastic samples based on light attenuation. Sample thickness woud be in the order of a few mm. I know that ...
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Book claims one can derive USCS mass unit "slug" from temperature equation shown in screen shots below
In the screenshots below, the author claims that one can derive the mass unit "slug" by somehow using the equation shown in the first picture. I understand how could derive a slug if you ...
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Distance sensors with accuracy of 0.1 mm?
I am looking for a sensor with 0.1 mm accuracy and a sensing distance of 1-10 cm for an industrial machine. The machine is used to ensure product quality following the assembly process. It will be ...
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Converting values from Tensile Strength tester to newtons
I have a Tensile Strength tester from TMI model 84-76.
I am getting data from this machine over the serial port. I don't understand what the values are that it is streaming during the test. I do know ...
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57
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Creative way to get accurate temperature without $$$?
I am looking for a way to measure temperature to about +/-1F (or at least +/-1C) accurate around room temperatures (50F-80F).
Currently I am comparing three different thermometers and the result is ...
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Orifice flow meter equation applicability, modeling leak flow
I am trying to determine the correct equation to model ideal gas flow rate through an orifice as a function of pressure. The equation below I found in Marks' Handbook for Mech Eng 8th Ed, p. 3-64 ...
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Any good scientific way to measure the ability of plastic to withstand compression force at home?
I want to test plastic's ability to withstand compression force scientifically. However, I don't have those compression machine. Are there other good ways to do it scientifically at home?
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Measurement inaccuracy using Digital Caliper
I am using a digital caliper (0.01-200mm) to measure the dimensions (in mm) of plastic blocks. In this case 3D printed blocks but the problem also applies to off the shelf products. The problem is ...
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Is a candy/oil thermometer suitable for calibrating a soldering iron or hot air gun? Why/not?
Disclaimer: not sure if the question is on-topic here, but I'm not sure that any other community is better suited. If there is one, would you kindly direct me there?
Background: I am looking into ...
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How to measure the electrical properties to ensure the performance of a thin electrode/insulator stack-up?
I am a mechanical engineer by trade, and I am looking at some basic electrical properties that I need to measure to ensure the device meets the desired performance. The device consists of a two-layer ...
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Finding and drafting a spline
I'm working with a friend to adapt a BMW steering wheel from the 2010s to his Logitech G20 steering wheel base.
Now, the BMW wheel is constrained in depth with a 90° taper, and in rotation with a 48-...
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Why does 4-wire resistance measurement change after a period of time?
I have a plug that I am measuring the resistance using the kelvin probe.
The plug is as below. The measurement is taken from the contact point of the plug the other end that has a PCB inside that ...
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Cost effective hand held medical scanner
I am currently doing a summer project where I am tasked with taking precise measurement of skin deformations, whether it be wounds or pimples, the measurement of the z-axis depth is what I am ...
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How do I measure groove separation?
In this drawing it says that each groove is separated by 5deg. Each groove has a depth of .015", the radius of the contour is 0.47"
How do I measure the separation of each groove?
My sketch ...
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Inverse analysis of one storey structure
The displacement history of one story structure is known due to an unknown ground motion. The dynamic properties, such as mass and lateral stiffness, are known, and dimensions were also given. How to ...
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Units of measurement for structural analysis
FEA engine
I'm using CCX finite elements analysis engine along with its pre- and post-processor CGX:
http://www.dhondt.de/index.html
https://github.com/calculix
Example
I'm looking at one example here ...
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I'm writing into a book about blueprints some of the things Im looking for are not readily avialable
I currently just writing notes about the item I am up to. I'm writing an artisanal war book about fun blueprints someone might like to do as all of the projects presented are brought to the table by ...
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In UK, are new smart energy meters secure?
I have read this newspaper article about insecurities in smart meters.
Some quotes from the piece:
To communicate with the utility company, most smart meters use GSM, the 2G mobile standard. That has ...
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3D displacement measurement of a small object with sub-micron accuracy
Say we have a small object for which we can choose its geometry and material (e.g, a spherical mirror with 5mm diameter). Or alternatively a point wise light source generating spherical waves.
The ...
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How are surface roughness specimens created?
I'm wondering how surface roughness specimens that are used to calibrate surface roughness machines are created. Specifically those in the 125-200 µin range. Is this typically done with vertical ...
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What kind of sensor can I use for measuring the rotational position and speed of a link in a fourbar mechanism?
I work in mechanism circuit breaker design. We typically use mechanism that utilize small Θ and we therefore measure using linear travel potentiometers. On this new design, I need to measure a larger ...
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Do automatic quick release mechanisms exist?
I'm imagining something like a cable tie that would automatically release after a certain amount of tension was applied.
I guess a very basic way to do it would be to use different diameter strings ...
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How can I measure RPM of an encased refrigerator compressor. I would like the resultant RPM reading as a variable DC output
I understand that there are very expensive meters that do this
; ex: Ono Sokki FT-7200 or FLuke, but I need a cheaper alternative.
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Monitoring a pump's efficiency with a lack of data
First off, I'm an IT guy and not an engineer. I've been tasked with figuring out and monitoring the efficiency of some pumps. Thing is, I don't have a lot of data to work with. I don't know the total ...
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Water flow measuring device for a simple ceramic water filter
I am looking for a solution that would allow me to measure water consumption from a simple ceramic water filter device (see picture below).
The meter must be relatively cheap, work without being ...
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253
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What should be the hole diameter (tolerance) at a given fixed diameter of the shaft?
What should be the hole diameter (tolerance) at a given (fixed) diameter of the shaft, to mate the head of the tripod and the guide shaft? For example, shaft diameter is 20mm.
Material of head detail: ...
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Anemometer in liquid
Does anyone know if there's an anemometer for fluid flow, or any speed measuring apparatus, that can work in liquid? I am planning to use it to demonstrate natural convection circulation.
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DIY linear position sensor IR switch - bad results
I have a test rig whereby a shaft (an M4 threaded bar) is being pulled ~11.5mm by a mechanism (rather not detail that) in about 20ms. I want to plot the movement of this shaft vs the mechanism pulling ...
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How are flat parallel surfaces made? For example gauge blocks?
I know about the "whitworth" 3 plate method for making a flat surface but even if you used the side of another of the same material there's no assurance that the two sides would be parallel. ...
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Direction of tube when measuring air flow
When doing pitot tube measurements, the pressure is measured in 2 places. At the wall (A), for the static pressure and against the flow (B), for dynamic pressure. Where the difference between these ...
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ISO 1101 & 14405: Required number of measurements for evaluation of dimensions and GTOLS
To my knowledge, standards ISO 1101 (for dimensions) and ISO 14405 (for GTOLs) make no statements whatsoever as to the required number of measurements for evaluation of quantities specified therein.
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How to calculate scaled speed
While working on a project I faced a difficult problem.
Let's say I have car at a 1/10 scale. Now if a real car drives at 10 m/s, it would take 3 seconds to travel 30m. If we look at the scaled car ...
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What are the effects of temperature on optical fiber waveform
I am attempting to measure temperature using a signal through an optical fiber. If I send a waveform through an optical fiber, how would temperature affect it?
I've looked here (Calculating ...
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Inaccurate flow rate measurements of an engine diesel fuel due to change of its viscosity
I am measuring the volumetric flow rate of a diesel fuel using "Turbines" flow meter, both in the supply and return fuel lines of an industrial diesel engine (Caterpillar 3512B – coupled ...
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Mounting an electric motor to a transmission: how to measure
I'm trying to fabricate parts to mate an electric motor to a manual car transmission (although, I think this is a more general question).
I need to connect this:
To this:
Like this:
The approach I'...
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How to take dimensions of an underground tank
We have a few underground tanks with only the manholes visible from the outside. All tanks are cubic-shaped. How can we accurately measure the dimensions (depth,length and width) of the tanks? Are ...
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Positioning accelerometer on a cantilever beam
What is the appropriate position to place an accelerometer, along the length of a cantilever beam, for the follwing two cases:
The beam is under sinusoidal excitation at the free end.
The beam ...
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How does the total pressure detector in a quadropole mass spectrometer work?
All quadropole mass spectrometers that I have seen provide a total pressure reading in addition to partial pressure readings for the selected masses.
The mechanism of the total pressure measurement is ...
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Using an NIST Calibrated Thermistor Meter with uncalibrated or unknown probes
Background:
I recently purchased a NIST calibrated thermistor meter for measuring temperature at work. This Digisense (20250-94) meter came from a seemingly reputable company, Cole Parmer, and we ...
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Why aren't there laser diode based monochromatic sources for optical flats?
So at work we have some bent things that we want to quantify for flatness. I went looking for optical flats and monochromatic sources.
Even on my favorite source of good-but-cheap stuff (MSC Direct), ...
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What is the difference between a 100 USD professional pitot tube and a 5 USD hobbyist pitot tube?
I would like to measure air flow speeds in a duct system for dust collection in a workshop. Relevant air speeds in the ducts are around 10-30 m/s. The ducts are circular tubes with a diameter of 160 ...
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