# Questions tagged [measurements]

Measurements, instrumentation, calibration and metrology.

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67 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 ...
349 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 ...
29 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 ...
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. ...
125 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 ...
120 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 ...
36 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 ...
85 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 ...
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 ...
45 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 ...
118 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 ...
29 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. ...
44 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 ...
149 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 ...
23 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). ...
48 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 ...
41 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, ...
2k 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 ...
76 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. ...
5k 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....
28 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 ...
230 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 ...
96 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 ...
2k 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.
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/...
64 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 ...
337 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 ...
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 ...
127 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?
153 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 ...
1k views

### Measuring vs gauging

How would one describe the difference between measuring and gauging? As I understand it at my company, we use a fixed tool to gauge something, but we will use a set ...
31 views

### What device would you use to set angles in two plates?

I am studying gauges for measurements and I can't find the answer to what device I would use to set angles in 2 plates.
47 views

### Can strain gauges radially be mounted on 8 mm diameter shaft for torque measurement for effective result?

I need to measure a torque on an 8mm shaft of an electrical motor on a prototypical device. The expected torque is ~15 Nm and for the data processing I intend to use an Arduino. One requirement which ...
2k views

### What is the engineering standard for filenames with fractions and inches?

I need to save some engineering files that need the thicknesses in the filename. Windows hates "/" or "\", so I can't use a simple fraction. Symbols like this... ⅓, ⅔, ⅕, ⅖, ⅗, ⅘, ⅙, ⅚, ⅛, ⅜, ⅝, ⅞ .....
43 views

### Measuring beats/bounce in a closed cubed glass

Suppose that we have a $2$ by $2$ by 2 $cm^3$ closed box, made up of glass, with thickness $0.1 cm$. Yes, it is a very small box. Let's say in that box there is a ball (also made with glass) with ...
78 views

### High impact force sensor?

I have a small table-like platform with two legs. Underneath each, I need to measure the amount of force. I want to use the difference between the two force measurements to estimate the platform's ...
357 views

### Strain gauge placement to measure a twisting beam

Where is it best to place a strain gauge to measure the twist of a beam? And what type of gauge is best? In my application, I have a small metal part which experiences a twisting and bending force. ...
53 views

### Can foil strain gauges measure strain normal to the plane of the sensor?

I'm wondering if anyone in the community has experience with foil strain gauges used to measure strain components that are normal to the plane of the sensor? If the strain gauge were pressed between ...
8k views

### Methods to measure diameter

I want to measure a tube's diameter with a precision of about 0.1 mm. I have a caliper but sadly the tube is wider than my tool. I would like to know what methods exist to precisely measure a ...
19 views

### Maximum height view-able in the box when looking through slit

The problem is illustrated in the picture below. A viewer looks through a slit and into a room. The problem is to find the maximum height of the wall in the room that the viewer can see if they are ...
2k views

### what is 1P frequency in rotor (wind turbine)?

In wind turbine, Is the number of revolution taken in 1s is called 1P frequency? If not, is it possible to find the 1P rpm from rpm measured for 1 hour (that is, I have 60 rpm data points from ...
390 views

### How do solar balloons work at high altitudes?

I am interested in the challenges that Solar Balloons face when flying. For example, the high altitude could cause drastic changes in: Wind speed Temperature Moisture How does the unique design of ...
151 views

### In what cases are the roughness values Rt and Ra used?

Roughness measurement instruments output those two values, where Rt is the distance between the top of the highest peak and the bottom of the lowest valley, and Ra is the average distance of every ...
183 views

### How do I measure mercury in a graduated cylinder?

Convention says to measure at the bottom of the meniscus, but I think the cohesion/adhesion balance of mercury results in it "bulging out" Do you measure at the top of the bulge (near the center) or ...
6k views

### What does 12 bit resolution mean?

I'm looking at this inclinometer and in the features it says "12 bit resolution." I'm looking for a resolution of up to a 1/10th of a degree but don't understand what the 12 bit resolution means.
4k views

### Rule of Tens/Ten to 1 Rule in Measurement and Inspection

I'm trying to clarify my understanding about the requirements [read: best practices] for measurement resolution and measurement confidence. The "Rule of 10s" is a commonly tossed around guideline ...
879 views

### How do you convert "kps" to Pounds per Square Foot (psf)? [closed]

I'm looking at a soil bearing capacity report, which has a column labeled "kips" and the values are followed by "kps". A "kip" is 1000 pounds, but I'm not sure how to convert from "kps" to psf. The ...
42 views

### AirFlow Measurement

I'm a software developer, who wants to create a monitoring system for an industrial airflow system. The airflow of the system is huge - between 15 and 20 cubic liters per minute. Here is my problem, ...