Questions tagged [measurements]

Measurements, instrumentation, calibration and metrology.

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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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Non contact measurement of short distance with high accuracy [closed]

I am looking for a sensor that can measure the distance to skin. It should be able to handle dark and light skin without much difference to accuracy. The measurement range should be around 1cm to 5cm ...
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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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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. ...
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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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4 answers
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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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1 answer
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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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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 ...
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3 answers
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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 ...
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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 ...
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1 answer
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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 ...
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1 answer
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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?
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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 ...
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What conditions to properly measure surface resistivity using surface resistance meter?

I have some JEDEC trays that I need to measure it's surface resistivity. I have a surface resistivity meter to measure it, but I do not know what environmental conditions it is supposed to be measured ...
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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 ...
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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 ...
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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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Direct way to measure perpendicular movement?

I'm planning a CNC machine build which will use many linear slides with bearing blocks moving on them. Some of these need to be in parallel with each other and others perpendicular to each other. It ...
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1 answer
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Is sensor measurement uncertainty the same with its calibrator?

I'm trying to calibrate a proximity sensor A with another proximity sensor B. Say sensor B uncertainty is already known from the data sheet. However, for sensor A the uncertainty is nowhere to be ...
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Help on IR Proximity Sensor Inaccuracy

I want to measure the depth of a burning soil using IR proximity sensor. The sensor will be placed 20cm above the surface of the soil and measures it perpendicularly. Problem #1: I'm quite concerned ...
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Measuring an irregular cavity

A friend has a compartment in the center console of his car, he has asked me to help resize, reorder and add padding to the compartment. Basically the kind of things I'd need to know are the ...
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1 vote
1 answer
340 views

How to add a Gaussian noise signal with zero-mean in a given data set?

I have a real-time velocity measurement data set in a excel (.xlsx) file. I want to add the Gaussian noise signal with zero mean in this real-time data to create three set of pseudo measurements. ...
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2 answers
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How to measure a screw pump spindle?

My boss ordered a screw pump driving spindle from an alternative maker. That spindle, as expected, cannot turn with the two idle spindles inside the housing. Now he is asking for the spindle ...
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1 answer
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Inconsistant load cell readings - (static) fiction perhaps?

First off I'm not an engineer so please excuse the simple language I use to explain my question! I have an arrangement whereby I have a steel plate suspended from basically a bridge. The plate is free ...
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2 answers
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How to visualise/measure airflow in sauna?

I'd like to visualise/measure the flow of air in sauna to optimise the ventilation. Is there a way to colour the air (non-toxic!!!) so I may watch the flow? Or is there any other accessible technology ...
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How do you calibrate an inverted U-tube?

Say you make a U-shaped glass tube. If you fill it with water you are able to measure gas pressure by looking at the height difference of the meniscuses. In an inverted one, by turning it upside down ...
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Why would a magnetic sight glass indicate a wrong water level in a surge tank?

In a pumping station that i work, there is a magnetic sight glass attached to a surge tank which I guess there is something wrong about it because when I isolate the tube, drain it and reopen the air ...
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1 answer
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Measuring axial force in trapezoidal screw jack

Does anyone know of a good solution for measuring axial force in trapezoidal screw jack, like this: https://en.zimm.com/product-catalogue/screw-jack-ze-series/ze-r-trapezoidal-screw/ ? Force magnitude ...
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In Solidworks Hole Toolbox, what is Thread Minor Diameter according to DIN 13-1

Dear StackExchange Community, I recently discovered how to use the Toolbox customization to specify new threads in Solidworks 2021 SP2.0, such as ISO fine metric threads (DIN 13-3- ... -9). However, ...
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1 answer
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What unit of weight is that?

Recently I was weighting stuff with my dad and as I was playing with one of the old 2 kg weights I felt with my fingers number "5". After cleaning and upon further inspection it turned out ...
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1 answer
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Internal Diameter or External diameter measurement? [closed]

I would like to know if there is a definite way to understand what kind of diameter is indicated on the dwg by just looking at a dwg. I work in a job profile where I need to add inspection points to ...
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1 vote
1 answer
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Tolerances in a pin-hole assembly

Hi guys, can someone explain how to do this question? This question is under Geometric Dimensioning and Tolerances and I am clueless on how to tackle problem like this. EDIT This is the explanation ...
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1 answer
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Safely Measuring Voltage from Solar Panels in an Experimental Research Field

I'm installing solar panels (not connected to the grid) in units out in a field for research we're doing that looks like this (this is an outdated image, but I can't find the updated one unfortunately)...
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Finding force distribution using accelerometer data

The team I'm currently working for is trying to compare bushings with different durometer ratings in the front suspension using single axis(z) accelerometer data during curb impacts. The current ...
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How to measure time taken to run SCPI commands? [closed]

We all know that every program takes time to run. Normally in Python, the time built-in Python library would be sufficient to measure time-taken to run code. How may I determine how long a SCPI (...
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How to use Spectroid app to measure low frequency vibrations?

I need to measure how low frequency (vibration) changes when going through different materials. The only possible way I found is by using Spectroid app. However, I have no idea of what settings to set ...
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Error propagation in reciprocal of a measurement

I have a measure of a quantity, x, and I know the standard deviation of the measure, STDx. I want to compute the inverse of x, which is y= 1/x, but then what would happen to the standard deviation? ...
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Is there an instrument that can measure thickness of an object through strain?

So basically, I am doing a project to design a measurement tool for measuring the different layers of the quartz crucible used in the semiconductor industry. Since the crucibles undergo some ...

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