Questions tagged [measurements]

Measurements, instrumentation, calibration and metrology.

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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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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?
lovedrinking's user avatar
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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 ...
lovedrinking's user avatar
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Circularity symbol with datum?

I am trying to interpret a technical drawing that has a datum attached to a circularity GD&T symbol. This page says that Circularity never has a datum reference. But this is a technical drawing ...
tar's user avatar
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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 ...
Gregorio Litenstein's user avatar
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Is British thermal unit written btu or BTU?

Should I write British thermal unit as BTU or Btu?
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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 ...
SNIreaPER's user avatar
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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-...
Vincent Guttmann's user avatar
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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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Unable to calibrate variable area flowmeter to VDI/VDE 3513-2:2008

I'm seeking your expertise to resolve a calibration challenge with a Krohne DK-37 variable area flow meter. Despite repeated satisfactory calibrations by the German manufacturer, we're experiencing a ...
Mike Shanahan's user avatar
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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 ...
tigerhoang03's user avatar
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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 ...
user5507535's user avatar
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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 ...
matthew wykoff's user avatar
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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 ...
Peter Bill's user avatar
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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 ...
Alejandro's user avatar
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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 ...
Georgije Stanisic's user avatar
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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 ...
olly's user avatar
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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.
YisroelM's user avatar
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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 ...
Tim's user avatar
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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 ...
Caserio's user avatar
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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: ...
Lexx Luxx's user avatar
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2 answers
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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.
FlakR's user avatar
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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 ...
KevInSol's user avatar
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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. ...
Jake's user avatar
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2 answers
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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. ...
chicken_game's user avatar
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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 ...
Mointy's user avatar
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1 answer
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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 ...
AEW's user avatar
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4 answers
253 views

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'...
JeffB's user avatar
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2 answers
173 views

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 ...
dInGd0nG's user avatar
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2 answers
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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 ...
Rahul's user avatar
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1 answer
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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 ...
Frido's user avatar
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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 ...
user391339's user avatar
2 votes
0 answers
36 views

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 ...
rasmuse's user avatar
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2 votes
1 answer
56 views

Alignment of bandsaw fence/knuckle

I'm looking for what I might be missing in trying to align the fence on my bandsaw. I have a Laguna Tools 18|Bx 3HP 220V 18″ Bandsaw, specifically a MBAND18BX2203. When I let them know the alignment ...
bonhoffer's user avatar
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3 answers
183 views

Figuring out Geometry for Kreg 720

I'm making pocket holes to connect wood together with a jig, the Kreg 720. The 720 works by moving at an angle (which I'm trying to measure) to ensure the hole is drilled higher on thicker pieces. The ...
bonhoffer's user avatar
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2 votes
1 answer
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How do you use an angle gauge?

I've come across this:- from https://www.amazon.co.uk/dp/B08WXFDRBX/. It says it's is for woodworking, but the vernier is marked into 2' segments. That seems a little too accurate for wood, and of ...
Paul Uszak's user avatar
1 vote
1 answer
177 views

DIY CO2 sensor calibration

Summary: Are there any worthwhile methods for rough calibration of CO2 sensors without proper chemistry lab equipment, calibration gas, or other known-good sensor available? It would only be used as ...
rockfort's user avatar
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1 answer
123 views

Why does Poisson's ratio always have the axial strain as the denominator?

Why can't we divide the lateral by the axial strain? Why does the axial strain always have to be the denominator? Would it matter if I was careless and accidently switched them around?
Anna Fakira's user avatar
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1 answer
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Flow Velocity Data Automation - Platform/Controller Selection

I have been tasked with (semi) automating flow velocity data collection using a pitot tube in a minaturized wind tunnel. The pitot is mounted on a two axis stepper motor system which is controlled by ...
Benjamin Price's user avatar
1 vote
0 answers
45 views

Looking for a loadcell in the shape of a truss rod

Today I found myself looking for force measurement device (load cell) that can be easily attached to a educational truss structure (i.e. replace a rod in a truss). I'm sure that there are bound to be ...
NMech's user avatar
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1 answer
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Doubt related to venturimeter and manometric fluid

I am unable to understand why the manometric fluid do not flush off due to high pressure fluid flowing through pipe? Because as discharge increases pressure drop will increase so manometer should show ...
Max's user avatar
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2 answers
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Do piezoelectric materials produce a current flow or just an electric field?

I was watching a video https://www.youtube.com/watch?v=uvT3XvDSSQw about piezoelectric materials. They mentioned that "a current can flow when a pressure is applied to the material". I have ...
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