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Questions tagged [instrument]

A measurement instrument is a device used to sample physical observations. Examples include pressure sensors, thermocouples, etc.

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Why do pipe organ tubes need to have different thicknesses?

In a pipe organ, there are many tubes—long and short, thick and narrow. Each tube presumably resonates at a specific frequency based on its length and produces a distinct note. Why do they have to be ...
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22 views

Digital Tachometer

How actually does a Non-Contact Type Digital Tachometer work? The answer which I could find is - The infrared light from them tachometer falls on the surface and gets reflected back to the ...
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How to do elementary plasma diagnostics?

How can I do elementary plasma diagnostics if I want to know e.g. the temperature of a plasma, if it is in thermodynamic equilibrium, the temperature of the various ionic species and the temperature ...
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23 views

Clarification on the three omega method for measuring thermal conductivity

I've recently come across the $3\omega$-method for measuring thermal conductivity in materials. Now I'm told that we use a lock-in amplifier to measure the 3rd harmonic in the voltage across the metal ...
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1answer
36 views

How do I find out the tension and the weight of a string with a given frequency?

I'm trying to build my own string instrument. I can make the string however long I want it to be, the instrument should play a B which is at 493.9Hz. What calculations do I need to do?
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35 views

Plasma Waves at Different Frequencies

I am trying to determine what plasma waves appear at what frequency ranges. Particularly, I am interested in exploring plasma waves occurring between 100kHz to 1MHz. Is this a bad frequency range to ...
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Please help identify this physics apparatus!

This was my grandfather’s and have no idea what it is only that it is some piece of physics equipment! The main black cylinder doesn’t seem like it wants to rotate but not sure if it should?
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2answers
666 views

What is the difference between a galvanometer, an ammeter and a voltmeter?

I'm looking for basic differences b/w the three with respect to nature of the circuit as well i.e either it is connected in parallel or series, and also the reason as to why they're connected the way ...
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68 views

Is Potentiometer a variable resistor or a measuring instrument?

I have used Potentiometers many times, and what I understood is that it is a variable resistor. However, my Physics teacher says that he is SURE a potentiometer is used to measure stuff, and is NOT a ...
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1answer
310 views

The Geiger Counter

In my class, we talked about the GM-counter and we were shown a graph with the voltage on the x-axis and intensity on the y-axis. But I do not understand why the graph has the characteristics it has, ...
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5answers
72 views

Is there such a thing as a work meter to measure work?

I know there are devices to measure power (e.g., dynamometers) but I can't think of any example of a device that measures work directly. Is there such a thing?
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3answers
59 views

Manometer physics? How to keep nozzles from draining?

Picture two liquid spray nozzles spaced vertically by some distance. Both nozzles are connected via flexible tubing to a single valve via a tee. Once the nozzle lines are full of fluid how can i ...
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1answer
552 views

What's the longest wavelength single photon we've ever observed? [duplicate]

At short wavelengths, our light detectors tend to be photon counters (e.g. CCD light sensor). At longer wavelengths, we use antennas and bolometers that tend to add up energy instead of counting ...
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29 views

How to devise a microwave power sensor?

I am fairly aware of the general thermistor/ diode/ thermocouple methods of sensing microwave power. Currently my requirements are simpler: A device that senses only microwave power incident on it - ...
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1answer
114 views

Effect of Lock-in Amplifier Phase Noise

Suppose that an oscillator with phase noise is used to drive a modulating process and that the same oscillator is used (with an appropriate phase shift) is used to synchronously demodulate the signal ...
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2answers
55 views

How should a hydrometer be read?

Probably due to surface tension the surface tends to curve near the hydrometer forming a meniscus. The question is whether it's correct to read the hydrometer at top of the meniscus or at the liquid ...
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1answer
39 views

How can the color of the sun be measured?

As the sun sets it changes color, sometimes first becoming orange, then red, for example. The device typically used to measure color is a colorimeter, but all of the colorimeters I have seen only ...
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0answers
207 views

How can I calculate the sensitivity of a seismometer?

I would like to know how to find the minimum ground motion a seismometer can measure, specifically if a certain seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but ...
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1answer
272 views

What does a retarding field energy analyzer measure?

According to [1], p.58, the current collected by a retarding field analyzer is: $$I= qA \int^\infty_{v_{min}} vf(v)dv $$ where $q$ is the electron charge magnitude (here singly charged ions are ...
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24 views

Calibration of LCD display type thermometer (without extended probes)

How can we ensure correctness of an LCD display type thermometer used indoor e.g. the HTC-1 which does not have extended probes.
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55 views

Comparing measurements from Sound Level Meters and Audio Recorders

I've been working with an environmental sound recording system that consists of a microphone -> sound level meter (SLM) -> digital audio recorder. Recently I've been involved with implementing a ...
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1answer
547 views

Can a virtual image be magnified?

It's common to encounter the diagrams of compound microscope describing its function. It consists of a real, magnified image formed by the objective and is further magnified by the eye piece. Can a ...
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1answer
133 views

Measuring magnetic fields [closed]

I have been working on developing apparatus for measuring the intensity of magnetic field in Physics experiments for the undergrad lab. Some solutions use miniature hall effect ICs to measure the ...
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2answers
153 views

Measuring nuclear magnetic resonance

We are in process of designing an NMR experiment for our physics lab. The equipment has been set and we obtained resonance frequency for some samples. The setup is a bit rudimentary with a very small ...
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333 views

Can you tell me what is the name of this scientific instrument?

Hello i need help to identify this old instrument. I only have this photo. Can you help me?
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2k views

Formula for lens periscope

I want to build a periscope. To my great surprise even after intense googling I could find little relevant information about periscopes anywhere on the internet. Let's say I want to build a ...
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1answer
667 views

Hot wire voltmeter

What happens when we use hot wire voltmeter to measure voltage across a resistor in a dc circuit? Does it show root-mean-square voltage or does it show the mean voltage?
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12k views

How do laser “tape measures” work?

There is a device available for about $\$40$, which fits in the palm of the hand, runs on two AA batteries, and can measure distances up to $50\,{\rm ft}$ to an accuracy of $\sim \frac{1}{8}''$ ($\sim ...
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1answer
418 views

A mathematical question on an Ultrasonic flow meter (Time of flight)

I'm trying gain a better understanding of expressions used to derive a formula to calculate the flow velocity Here are the following expressions: $$t_d= \frac{L}{(v+ucosθ)}$$ $$t_u= \frac{L}{(v-...
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1answer
970 views

Why do we prefer using materials of high resistivity in laboratory instruments?

I know that :$$R=\rho\frac{l}{A}$$ where $R$ is the resistance of the wire, $\rho$ is its specific resistance (resistivity), $l$ is its length, and $A$ is the area of cross-section of the wire. Why ...
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221 views

Software engineer vs physics engineer vs computational physics [closed]

Don't know if this question is off topic, but i think it is the best place to get an answer. I am finishing the 3rd year of a degree in physics engineering. I enjoyed the first year, but in the ...
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1answer
170 views

Double slit experiment mechanism

Can someone explain the mechanism that sets in motion the electrons in the experiment? Is it an electro-magnetic force? If so, I think it's not right to describe the motion of the electron as a '...
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1answer
5k views

What affect does pipe diameter have on a manometer? [closed]

I am building a DIY hoover and want to test different technical configurations of the device (hose diameter, hose length, motor RPM, motor voltage, cavity size, etc). My objective for testing these ...
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2answers
35k views

Why do voltmeters and ammeters have high and low resistance respectively?

I understand why voltmeters are connected in parallel and ammeters are connected in series, but why is it that to measure voltage, you must have high resistance, and to measure current, you must have ...
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341 views

Why vacuuming an air chamber is much slower than vacuuming an argon chamber?

When pumping a chamber full of air down to a certain level of vacuum, it takes a while. However, when that same chamber is full with argon, reaching the same level of vacuum is much faster. What makes ...
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92 views

How to set up an electrobalance?

My school has the instrumentation for a Guoy balance magnetic susceptibilty experiment: CENCO electromagnet and Cahn-Ventron RM2 electrobalance and a mounting stand for the balance. Unlike the ...
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15 views

Atomic Absorption Spectrophotometer

What are the advantages and dis-advantages of single beam V/S double beam Atomic Absorption Spectrophotometer? I am having a basics knowledge of Atomic Absorption Spectrophotometer but when ...
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1answer
60 views

Measuring mass zero G [closed]

I work for a company that produces (among other things) a microbalance that can measure mass/weight from around 100ng to 100mg ie it is accurate over 6 orders of magnitude. However, this relies on ...
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1answer
612 views

Where are the negligible and infinite resistances, respectively, of the ideal am- and voltmeter?

Consider the picture below. An ammeter is shown to the left, a voltmeter to the right. They consist of a d'Arsonval galvanometer, which is a coil (with a pointer attached) that can rotate in a ...
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1answer
239 views

Why is responsivity quoted as a figure of merit?

Lately I have been investigating the physics literature on proposed photosensitive electronic devices made of graphene. Often I see responsivity values quoted as if they suppossed to impress, and ...
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2answers
13k views

What does a speedometer measure?

When speaking of the velocity of a particle, we must specify a reference point. The same holds when we talk about the speed of a particle (is this correct?). If so, a speedometer measures instaneous ...
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2answers
428 views

What is the link between observation wavelength and spatial resolution of an instrument? [closed]

It seems that when capturing and emitting EM waves matter proceeds differently depending on the wavelenght. According to an answer from another question, EM energy is captured following three modes: ...
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0answers
400 views

Key and lock, which one is made first? [closed]

I know my is question is off-topic, but I can not find a suitable SE site for this question. Forgive me. I'm just curious about the order of producing a key and its lock, and the reason or procedure ...
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118 views

For thermal mass flow measurement technologies is it necessary to measure gas pressure to determine volumetric flow rate?

Mass flow readings from thermal mass flow measurement technologies often provide output readings in volumetric units (e.g. standard liters per minute). Mathematically I can derive the volumetric flow ...
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35 views

Hot wire anemometry and gas species

Hot wire anemometry is a technology that measures mass flow of a gas stream in the neighborhood of a heated wire. The sensitivity of a flow sensor using this technology is usually specified for a ...
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1answer
193 views

Why Microchannel Plates can be operated only in vacuum?

Why it is said that the Microchannel Plates can be operated in vacuum? What is the maximum pressure in which it can be operated? Also, while it is not operating, should it be kept in vacuum? Is this ...
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1answer
286 views

What is making these subatomic honeycomb shapes and gaps in this graphene image?

I just read yet another graphene discovery and saw this STM image: Nice photo, it begs two questions: What is that secondary honeycomb structure, the one about 20x smaller than the atoms themselves? ...
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1k views

Why must an integrating sphere be a sphere?

Why must an integrating sphere be a sphere? Why can't it be an integrating cube? What is the difference? Could I use a cube to measure total illuminance like an integrating sphere does?
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1answer
132 views

In a non auto-ranging digital multimeter, what do the increasing numbers in the Ohm section represent?

For my science fair project I am measuring the resistance of nichrome wires under different conditions. I am using an Innova 3300 digital multimeter to measure the resistance. Other websites have told ...
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93 views

The things to consider when choosing a mesh for an electron detector (MCP detector)

I am designing a electron velocity map imaging setup. I need a copper mesh just infront of the detector to accelerate the electrons towards the MCP detector. I am doing the instrument design for the ...