Questions tagged [measurements]

Measurements, instrumentation, calibration and metrology.

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17
votes
6answers
3k views

How can I measure correctly with a ruler?

When measuring with a ruler divided into mm lines, should I include the lines by themselves or only in between them? I illustrated the problem. (I took an example of measuring of 10 mm with two long ...
2
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2answers
38 views

Why are 0-10V signals de-facto standard in HVAC applications, when 4-20mA is more common in other applications?

I've been involved in a few projects with HVAC systems, where sensors etc. generally used 0-10 V signals, and looking at catalogues of Buderus and other suppliers this still appears to be the standard....
0
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1answer
60 views

How do engineers work with extremely small objects?

Please excuse me if my question is not well-worded. My background is pure mathematics and I am not familiar with engineering, but sometimes I feel fascinated by the things engineers have achieved. ...
1
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2answers
26 views

Accurate method or instrument to measure density of shaving cream foam or whipped cream foam?

I am currently filling a "standard" stainless steel cup of known volume with foam and then I weigh it. Then I calculate density. This method is pretty messy and I have to be careful about how I fill ...
0
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0answers
20 views

Estimating trunk rotation using frontal and sagittal views

I am doing an experiment regarding elbow flexion's effect on peak sprinting velocity and we want to measure trunk rotation and shoulder rotation during our trials. We don't have an overhead camera so ...
1
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2answers
51 views

Measuring a pattern size on a flat surface

I want to manually measure the dimension of a pattern printed on a flat surface, with an accuracy of about 0.1mm. For simplicity sake, let's say this is a black rectangle, printed on a white ...
0
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0answers
18 views

How to measure and create PVT diagram

We have all seen PVT diagrams. From my understanding one should measure pressure, volume and temperature on or near the outside of the system. Volume: maybe by displacing water initially and then ...
0
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0answers
25 views

How to design a method to estimate vx=speed in direction of swimming

We have a body that goes underwater (let's say a whale) with magnetometer and accelerometer data. I also have GPS, date, depth, pressure and temperature data. I want to know if there is any simple way ...
1
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1answer
36 views

How to measure the power output of a stirling engine

I'm doing a project for thermodynamics where I have to measure the power (work over time) of a Stirling engine for varying temperature differences. I don't necessarily need an exact answer (as in: ... ...
-1
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1answer
38 views

What are the simplest available methods for monitoring pressure and airflow in a 22mm diameter pipe?

In the emergency case that more than one person must share a mechanical ventilator, the medical professionals lose per-patient monitoring of pressure and airflow. To that end, what are the simplest ...
1
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1answer
54 views

How to reduce oscillations (rapid changes of control signal) when controlling a real system, which occur due to noise in measurement from sensors?

I have a real mechanical system (ball & beam) which I want to control. The system is approximated by the second order transfer function: $$ T(s) = \frac{b_0}{s^2+a_1s+a_2} $$ and in state-space ...
0
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0answers
30 views

What is dead beat reading?

I was reading about characteristic of a comparator. It states Comparator indicator device should be such that the readings are obtained in least possible time and for this magnification system should ...
-1
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1answer
32 views

Expression of uncertainty measurement

I have a problem with the expression of a measurement result. I have a resistance decade box used as variable resistor in order to balance a Wheatstone Bridge. Let's call this resistance decade box $...
0
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1answer
16 views

Measuring EM radiation power over surface area

I didn't make it obvious enough below that I was interested mostly in infrared, as the current use case is measuring power radiated from warm objects and from the ground. As pointed out in comment by @...
0
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1answer
55 views

BJT Output Characteristics Question

Ok, so I am pretty confused at the moment with a question that I have been given to work out by my lecturer and was wondering if I could get some guidance with it. I will attach images of the question ...
1
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0answers
15 views

how do you calculate viscocity from torque arm load cell measurements?

I have a piece of company developed equipment that uses a pot mounted on a rotating base plate with a 0.15m torque arm and load cell, a mixing paddle is used to stir the mixture while the controller ...
2
votes
0answers
50 views

How can I calculate the smallest voltage a given adc can read?

I have a project where I'd need to measure small voltage (0.05 mV) output of a wheatstone bridge with an arduino mini pro. Based on my previous question most probably it can't be done with its ...
0
votes
1answer
42 views

what is the range of the measurable relative elasticity with a commonly used strain gauge

I'm looking for a data that what is the typical application range for a common uni directional strain gauge like used in weight scales? I've read about around 200 ppm in a research gate article, can ...
1
vote
1answer
33 views

what does 0.1% FS +/- 0.02 mean?

Let's assume a DMM is specified to have accuracy "0.1% FS +/-0.02" when used on the 50 V range. I get that 0.1% FS means the true value will lie somewhere between measured value - 0.05 and measured ...
0
votes
1answer
51 views

Weight percentage and grams per liter

I was reading some documents that said 25 wt. %, 500 mlL-1 as well as 20 gL-1 I think 25 wt. %, 500 mlL-1 is referencing 25% weight of 500 ml of water so that would be 125 ml of water 20 g*L-1 would ...
2
votes
1answer
26 views

Calculate FTIR-system response functions from measurements of a calibrated black body

I need to find the response of my FTIR spectrometer. I do have a calibrated black-body source (area-emitter) which I measured at various temperatures. The system operates in inverse cm, cm-1. My ...
0
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0answers
16 views

Thermal radiation measurements: Looking for ~100 Hz BW, broadband (1-20 um) NIR/MIR detector

I am looking for a detector with about 100 Hz bandwidth, that has broad and ideally uniform absorbtance in the 1-20 um range. I need to be able to pickup signals in the 1 uW range with SNR >10, ...
0
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0answers
31 views

Why is there no widely-used standardized unit for indentation hardness?

The last hundred years have seen a great degree of standardization of units, and the expression of units of measurement in standardized, instrument-agnostic, objective terms, often in the SI units. ...
0
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0answers
14 views

How to measure rack-like construction structural integrity?

I need to measure structural integrity of quite big rack-like constructions (size of tens of meters, indoor conditions). The construction is already built and the additive sensor and processing system ...
2
votes
3answers
62 views

Sylvac UL 4 - USB - (Send data) reports 'no.data'?

Using the sylvac UL 4 Each time I invoke the (send data) function the sylvac LED panel reports 'no.data'. To mention the obvious but nothing is received at the connected USB device. My question ...
0
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1answer
72 views

Why does Bourdon tube measure relative pressure?

From Wikipedia: Bourdon tubes measure gauge pressure, relative to ambient atmospheric pressure, as opposed to absolute pressure; But looking at pictures such as the one above, it seems there is ...
-1
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1answer
35 views

Way to digitally measure volume of air inhaled by lungs?

I was interested in this as a fun project. To be able to get the volume of air inhaled by a person has some cool applications I can think of. I was thinking of a modified anemometer of sorts fitted ...
0
votes
1answer
71 views

off-scale torque measured - what is my torque arm?

I have assembled a benchtop torque measurement stand for evaluating electric motor and controller efficiency. The motor is 49kV , 5kW brushless outrunner. Input power reading is taken from motor ...
3
votes
1answer
38 views

What's the most practical way to measure angular velocity for small rotations?

I'm looking to measure the angular velocity of an arm as it moves. It seems to be a difficult thing to research, since the term 'angular velocity/frequency' is usually reserved for other areas of ...
1
vote
2answers
43 views

Measuring viscosity with tools other than viscometer

I would like to measure viscosity, but do not have access to a viscometer. If possible, I would like to avoid having to purchase one. I have access to many other flow measuring devices, including ...
2
votes
3answers
79 views

Cutting a larger circle on center of a smaller circle

At work, we cut a 6" hole in the wall for a duct. Later we decided we now want a 10 inch duct in the same place. what tricks are there to center the larger hole over the center of the smaller hole if ...
1
vote
1answer
28 views

Bolt circle indication on angled ellipse

Ok so I am a machinist, not an engineer, but figured someone here might be able to provide some insight into my situation. The part is 2.75" diameter and is on a 3.3* angle in the X axis on my mill. ...
1
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1answer
39 views

Whats a reliable way to measure the amount of rope going out of a coil?

I am an undergraduate researcher and I am working at enhancing a calibrating system for a hydrographic surveying system that my supervisor uses on his hydrography course. The rope is used to lower a ...
1
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0answers
77 views

Which imperial units of measurement use vulgar (simple) fraction numbers?

All values of metric units are expressed in decimal or scientific notation. Some imperial units, use fraction numbers as primary notation (3/4" for 0.75 inch). As far as i know, only inch and foot ...
0
votes
1answer
22 views

Measuring wire damage using strain gauges

We need to determine the physical damage in some area of overhead lines that can't be inspected visually. The damage's in general caused by short circuit and air pollution (mostly sulphur compound). ...
1
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0answers
38 views

How much does loading a load cell in other directions than the direction it was designed for effect the readings?

I am looking into using this TAL230B miniature type load cell to measure forces in x and y direction. The normal sensor loading is displayed in image 1. What is the effect of loading them as in image ...
1
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0answers
26 views

Strange offset on oscilloscope channel

I've a Rigol DS2072A. It works great except for an offset problem that I noticed the past few days. Channel 2 always shows a DC offset. This is independent of any settings such as channel coupling, ...
1
vote
5answers
594 views

Plumbing Imperial units confusion - 3/4" is supposed to be around 19mm, right?

I'm really confused. I've only ever used metric in my life. Recently I'm trying to build a IOT device and there is plumbing and water involved. I was looking for a 19mm fitting, but on Amazon and ...
0
votes
5answers
64 views

How can I get the horizon or vertical length of the uneven object?

Just like the picture shown I want to have the length from the front end to the windshield in horizon, and want to have the length from the lowest point to the highest point of the hood in vertical. ...
0
votes
3answers
1k views

Confused as to how to read this caliper

Here is a picture of a caliper that I found: Calipers are such basic tools, but I have trouble understanding how they work. Here the main scale says "mm" at the end, and the Vernier scale says "0....
2
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0answers
26 views

How to measure the inertia of an object using a motor

first time on this board even if I've been lurking for a while. I'm a tennis racquet technician and, for the sake of saving some money and just for the fun of it, I'm trying to build a machine that ...
-1
votes
1answer
159 views

Must MSA (Measurement System Analysis) be re-performed after annual instrument calibration?

I'm working in an automotive company that must follow IATF (International Automotive Task Force) requirements. I administrate a test-bench that performs RF (radio frequency) tests using an ...
1
vote
1answer
73 views

What measurement accuracy/precision is required to detect a 10% relative change in the measured quantity

I'm trying to design a measurement system, the primary objective of which is to reliably detect a 10% change in the the volume of fluid flowing through a pipe. I'm struggling to come up with a ...
0
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1answer
952 views

What are functional and manufacturing datums

Can somebody please explain what is ment by functional datum and manufacturing datum, with respect to dimentioning and tolerancing.
0
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2answers
39 views

How to measure number of strokes in a small space

I have read about a device called drumometer, which measures the number of strokes of hitting drum stick. I think this is almost the same, but instead, I would like to measure the number of strokes/...
2
votes
0answers
54 views

Maintaining constant speed of a CVT engine during a slope

I am not sure if this question is related to this community. But nevertheless. I work on CVT engines, I had a new idea of modifying my controller during a slope or a gradient on the road so that the ...
0
votes
1answer
197 views

How can I measure the coefficients of friction of pulleys?

I have to study several industrial pulleys made for lifting heavy weights. It is important to select one which has a low coefficient of friction because the system is based in a hoist and several ...
2
votes
1answer
1k views

What is the difference between direct and indirect reading instruments

I need to know the difference between a direct and indirect reading instrument. Would a caliper be a direct and a gauge block be indirect? Is a direct instrument something with a variable measurement ...
0
votes
1answer
69 views

Typical range of a small hole gauge.

I want to get this out there. What is a typical and common range of a small hole gauge?
1
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1answer
105 views

How accurate must my gauge be?

Is there a general rule of thumb for how accurate a gauge should be in compared to the parts being checked? In my chemistry class, I remember making standards where the instrument needed 1 more ...