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Questions tagged [measurement]

Measurement is the assignment of numbers to objects or events. All measurements consist of three parts: magnitude, dimensions (units) and uncertainty.

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What's the most economical way to digitally measure 240V mains voltage, current and power factor?

I'm looking to capture and analyse measurements of the mains energy that I use per circuit. I've found a few consumer products that offer powerpoint energy monitoring such as the Kill-A-Watt, but PC ...
i336_'s user avatar
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25 votes
5 answers
5k views

Help learning from a mistake connecting an oscilloscope

I have built this circuit to dim a lamp with a PWM signal. It had an issue where the MOSFET was getting really hot. So I wanted to know what was happening on the gate of the MOSFET. I turned the PWM ...
cyrili101's user avatar
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17 votes
4 answers
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How do I measure differential signals (like RS-485 or DMX) on an oscilloscope?

I've encountered differential signals in a few places, such as a differential output audio amplifier and now in a project working with DMX which is similar to RS-485. (Here's a similar question about ...
JYelton's user avatar
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24 votes
13 answers
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Level of a water tank with a microcontroller

How do i measure the level of a water tank with a microcontroller?
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14 votes
2 answers
19k views

What are the differences between a x1 and a x10 oscilloscope probe

I've heard pros of x10 oscilloscope probes a lot. Now I need to know the cons, but I couldn't find a clear explanation. Some people say x1 probe is for small signal. How do you decide either x10 or x1?...
ryunika's user avatar
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13 votes
1 answer
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Measuring ferrite core parameters

I have large amounts of inductors and transformers from power supplies or other undocumented sources. They are of course completely unmarked and I have no idea what kind of ferrite material they are ...
jpc's user avatar
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6 votes
4 answers
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What is the noise level as read on my oscilloscope?

The above is what I'm seeing on my oscilloscope. It's zener diode noise. Scope's set for 0.5V/div vertically, and 1ms/div horizontally. The oscilloscope has a 20MHz bandwidth, but the noise doesn't ...
Paul Uszak's user avatar
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5 votes
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How to measure capacitance without LC meter?

I would like to use capacitors salvaged from old electronics, but I currently don't have an LC meter. What would be some really simple circuits, that would convert capacitance to something I can ...
nana's user avatar
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5 votes
1 answer
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How to measure supply currents ranging from 1μA to 10mA?

I’m building a battery powered data logger with a microcontroller and several sensors. I’d like to measure the supply current of individual parts with idle currents in the μA range and peak currents ...
Michael's user avatar
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2 votes
4 answers
7k views

How does 3-wire RTD or resistance measurement works in bridge of wheatstone?

I cannot understand how 3-wire measurement will improve the resistance measurement. They say that IF lead resistance \$ R_L \$ is the same, it will compensate. How can this happen? If bridge is ...
Kono's user avatar
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12 votes
6 answers
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Measuring frequency of a signal above 5V with a microcontroller

I want to measure the frequency (up to 300 Hz) of a rectangle signal, that varies between 0V and Vtop, where Vtop is anything between 5V and 15V. Because I cannot apply more than 5V to the ...
PetPaulsen's user avatar
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11 votes
1 answer
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How does autoranging work in a multimeter? What is the circuit?

I was curious how this is done. It seems you would have to vary the voltage and current to measure resistance from 1ohm to 10Mohm.
Bill's user avatar
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10 votes
3 answers
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Understanding capacitance in oscilloscope probe tip

I am trying to understand the capacitance and resistance in oscilloscope probe tip. In the above attached image, that 9Mohm resistance is used for that 1x and 10x setting that divides the input ...
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9 votes
3 answers
7k views

How to measure the quality of a USB charging cable?

I have a set of USB cables (data and charge) and I noticed that, for a given charger, the charge time differs by cable. What would be a good way to measure the charging fitness of a USB cable? ...
WoJ's user avatar
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8 votes
5 answers
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Water level detection, where water is somewhat polluted and has significant dissolved salts

Found this excellent QnA here which provides several options for measuring or detection water-level. For my case, it is enough to differentiate 4 levels of water (very low, low, middle, full), of the ...
bdutta74's user avatar
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6 votes
2 answers
264 views

Current measurement maximum time

On my multimeter I have two current measurement connection. One for the mA and one for the A. On the ampere one there's a time limitation but not on the mA one. Also they mention in the manual a kind ...
Emmanuel Istace's user avatar
6 votes
4 answers
12k views

Precise Resistance Measurement Techniques

This question is inspired by some basic questions on resistors I've read here lately. What's the most accurate/precise technique for measuring the value of a resistor you can think of? What level of ...
vicatcu's user avatar
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6 votes
2 answers
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How to measure power consumed by mains device

I would like to measure the power consumed by a mains device. I have heard that it's not as trivial as simply measuring the average current, as the device may be resistive, capacitive or inductive, ...
Rocketmagnet's user avatar
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5 votes
3 answers
12k views

Detecting dry-running of water pump

What are some reasonably reliable ways of detecting that a water pump (electrical motor based) is "dry running", i.e. no water is passing through the pump either because there is no water available at ...
bdutta74's user avatar
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4 votes
2 answers
2k views

ADC calibration in ATTiny88

I'm writing an embedded app for ATtiny88 - one of its task is to measure voltages of serial connected two 12 V car batteries. The microcontroller is powered from around 4.5-5 V (LM317), measured ...
Adam's user avatar
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4 votes
4 answers
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Oscilloscope: How are Bandwidth specification and Sampling Rate related?

I had thought that a (digital) Oscilloscope with higher Sampling Rate, would automatically have higher Bandwidth. That seems intuitive because of Nyquist Sampling Theorem. But I've read in several ...
user246185's user avatar
3 votes
1 answer
2k views

How does one measure the power factor?

How does one measure the power factor? $$\text{power factor}\equiv\frac{\text{power}}{|V||I|}=\frac{R}{\sqrt{R^2+(1/\omega^2C^2)}}$$ for an RC circuit driven with \$V(t)=V_0\cos{(\omega t)}\$.
Geremia's user avatar
  • 473
3 votes
1 answer
10k views

How to take Time Measurements using LT Spice

I've been fooling around with LT spice .MEAS feature for a while now and I just can't seem to determine how to take the time measurements I need for an assignment. I can look at the time values on ...
Cody Richards's user avatar
3 votes
3 answers
2k views

Simplest way to check if an audio level is line or micro?

I can check level audio on a VU Meter or dBFS meter. What's the simplest way to check if an input audio level is line or micro? Can I use a multimeter?
ark1974's user avatar
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1 vote
2 answers
411 views

How isolation is achieved in isolated channel oscilloscopes?

I tried to search something about this but found only a small amount of information. What confuses me is that all isolation amplifiers, optocouplers etc. I could find usually work at much lower ...
Dmitry's user avatar
  • 23
1 vote
1 answer
1k views

Measuring an AC-voltage at the ouput of a full bridge rectifier

I've a full bridge rectifier and I put the following function into it: $$5\sin(100\pi t)\tag1$$ So, at the output I get: $$\left|(5-2V_d)\sin(100\pi t)\right|\tag2$$ Where \$V_d\$ is the voltage ...
Looper's user avatar
  • 331
1 vote
2 answers
2k views

Measuring Inductance

I have been looking the number of methods to measure inductance of a coil if you don't have an LCR meter available, and I have had some difficulty. I designed and built a coil and I would like to ...
Dave's user avatar
  • 429
0 votes
1 answer
898 views

Measure small capacitance value

I need to measure C value continuously over time, and save the value to some text file (csv for example). Note that C changes over time, since the system is dynamic. C are small, varies between 50 to ...
Dzung Nguyen's user avatar
20 votes
13 answers
10k views

Why only sine waves?

I have already read a few EE texts where a sine wave is often seen. Why is the sine wave often used as a test function for a circuit or a system? Why don't we use any other signal instead of sine? ...
DSP_CS's user avatar
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17 votes
3 answers
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What kind of oscilloscopes are qualified for measuring USB 3 Super Speed Signals?

I understand that they probably will be very expensive. But I have little idea of what kind would qualify. How much bandwidth? At what sampling rate? Any other parameters?
J.L's user avatar
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17 votes
7 answers
128k views

Physically determine unknown wire's gauge

Is there any way to easily and accurately determine the gauge of stranded wire by measuring it? I know you can pretty easily determine the gauge of solid-core wire with just a pair of calipers by ...
Connor Wolf's user avatar
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15 votes
3 answers
3k views

How can I measure gate capacitance?

Is there an effective way to directly measure the gate capacitance of a power MOSFET, like say the IRF530N? The way my circuit is behaving would indicate that the effective gate capacitance is ...
scanny's user avatar
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13 votes
4 answers
3k views

Why does it take time for electronic scale to measure?

If I am standing on a digital scale or measuring the weight of my luggage, the display doesn't show the weight immediately - it takes a few fractions of a second. Why is that and can you overcome it ...
Sharon G's user avatar
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13 votes
7 answers
22k views

What does a half-digit mean in case of accuracy?

What does it mean when somone says something like "3 and 1/2 digit" in case of accuracy of test equipments (or maybe A/D converters?) Can somone explain this a bit with some numbers as ...
Dumbo's user avatar
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13 votes
7 answers
6k views

Soil moisture measurement

Background To kick-start my longstanding ambition of getting back into electronics, I decided to try and make a device that measures the soil moisture of potted plants to determine whether they need ...
drxzcl's user avatar
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12 votes
4 answers
17k views

Digital bathroom scale circuit - how it works?

I'd like to understand how the digital bathroom scales work. I was able to gather that there are four three-wire load cells connected into the Wheatstone bridge as suggested below. The load cells have ...
YSN's user avatar
  • 299
9 votes
7 answers
20k views

Measuring 0 - 1MHz ( 0.25Hz resolution) Squarewave using an MCU

I need to measure the frequency of square-wave that can vary between 0 and 1MHz, and has a resolution of 0.25Hz. I havent decided on which controller yet but It will most likely be one of the 20pin ...
volting's user avatar
  • 897
7 votes
5 answers
56k views

Can't get a precise reading with PT100 temperature sensor

I am trying to get more precise temperature value from PT100 ( 2 wire ) sensor with Arduino. Here's how my circuit looks like : When the sensor is about 20 °C I get a value on A5 pin that is 432 and ...
Muhamed Krlić's user avatar
7 votes
2 answers
5k views

How is a 50Ω "back-termination" accomplished on a scope probe line?

I've just been watching Jim Williams' very excellent video on Measuring Switching Regulator Noise. At 1:58 Jim mentions a "50Ω back termination" in the probe setup that looks something like this (but ...
scanny's user avatar
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7 votes
3 answers
1k views

Will this approach accurately measure capacitance and infer spacing?

I am interested in any feedback or caveats regarding the following capacitance measurement method before I begin setting it up. For an experiment, I have come across the need to measure and track the ...
sasha's user avatar
  • 553
7 votes
5 answers
4k views

Predicting thermal equilibrium: what's wrong with my time constant?

I understand that this is arguably a peripheral electronics problem, but it seemed to fit here better than in physics. I've been doing some power electronics design work with large IGBTs mounted on ...
Stephen Collings's user avatar
6 votes
5 answers
6k views

Can DAQ devices be used as Oscilloscopes?

Recently, I took computer architecture course, and got interested in analog electronics. At present moment, I can't afford good USB oscilloscope such as Agilent or Cleverscope (though, they are not ...
newprint's user avatar
  • 217
6 votes
2 answers
9k views

Vector Analyzer: what is IF bandwidth?

I noticed that if I set IF bandwidth low, the measures done with a vector analyzer are better (with higher SNR) but it is slower. Precisely, what does it happen when I change it? Can you explain me ...
Kinka-Byo's user avatar
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6 votes
4 answers
744 views

Using 50 Ω coax cable instead of passive probe

Preface, why am I asking this question? Instead of using a passive probe with a ground clip, I want a more "permanent" and reliable connection for my measurements. Note: I'm not talking ...
Marco's user avatar
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6 votes
3 answers
6k views

Oscilloscope: when to use coaxial instead of probes?

I understand the difference between passive and active probes, and between x1, x10, x100, ... I also understand that at high frequencies the capacitance of the oscilloscope has to be considered, so a ...
Dylan's user avatar
  • 101
5 votes
1 answer
124 views

Can I use 12 V and -12 V together?

I am sorry if this question is pretty easy but I am a beginner. I have a PC PSU that provides two lines: 12 V 11A -12 V 1.5A If I used them together will I get 24V, and how many amps can they provide?...
Mohamed Essam's user avatar
5 votes
3 answers
1k views

Is it possible to calculate effective value of a signal from its average value?

I have a signal which I want to calculate its effective value. The signal is a voltage value read on a 33.3m\$ \Omega \$ resistor connected series to a 220V AC power line. My aim is to calculate the ...
hkBattousai's user avatar
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5 votes
3 answers
8k views

What is the test voltage of a ohmmeter?

Ohmmeters don't appear to make LEDs conduct which gives overestimates in the resistance measured (tested with a R1//(R2+LED) parallel circuit). So what is the voltage they apply to the circuit, ...
Mister Mystère's user avatar
5 votes
4 answers
2k views

Schrödinger and electrical measurement issue

During the 19's, Schrödinger state that it is impossible to make a measurement without disturbing a system. To illustrate his statement, he made the famous experiment of the cat and the box. Poor cat ...
M.Ferru's user avatar
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5 votes
3 answers
489 views

Which components can be measured while soldered on a PCB board already?

I am assembling nonlinear oscillators on PCB boards for applied math research [Colpitts (100 kHz, 3 V_pp), FitzHugh-Nagumo (100 kHz, 15 V_pp)]. I am working with some other people that want to do ODE ...
KBL's user avatar
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