Questions tagged [frequency]

How many times something happens per second, measured in Hz (Hertz).

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Peak/envelope detector circuit for 30 MHz sine pulses with a 10 kHz PRF

My goal is to input 30MHz sine pulses, with a pulse width of 10us and gap of 90us between the pulses. The circuit should convert this pulse train to a TTL signal that goes from 0 to 5 volts. To ...
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Hark There is an Arc

AC mains power is almost always transmitted at 50 or 60 Hz. Accepted reasoning is that lower frequencies make transformers larger and higher frequencies have greater transmission losses. ...
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How to calculate frequency of an AC source with variable frequency using Arduino

I have an AC current source. Its properties are Maximum Vrms=15v Maximum Frequency 125 Hz Minimum Frequency 5 Hz The current source is pickup coil of a motorcycle... Vrms range is approximately 0.7v-...
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6 votes
2 answers
540 views

Can the frequency of voltage change throughout a circuit?

I am currently doing a project which involves taking a circuit of resistors, inductors, and capacitors (combined in any way imaginable) and finding the total impedance of the circuit. For the latter 2 ...
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Change clock frequency from 50MHz to 40MHz using Altera Cyclone IV and Quartus Lite 20.1

I'm using the FPGA board EasyFPGAv2.2 which have Altera Cyclone IV with chip EP4CE6E22C6 and I made a verilog program to generate VGA 640x480 60Hz signal. It works great dividing 50MHz by 2 generating ...
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Mimic a thermistor/variable resistance signal using PWM

I am looking for a way to create a variable resistance signal to mimic the signal that would typically be provided by a thermistor, but by using a digital signal that switches to ground. I currently ...
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4 votes
3 answers
509 views

Are microphones with flatter frequency response charts better at picking up frequencies?

I am doing an experiment where we measure the frequency using computer microphones and use Audacity to find the peak frequency. If there was a sound at 1kHz, would a better microphone pick up the ...
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What is the tradeoff in decreasing the frequency bandwidth when reducing noise of a resistor?

A resistor's Johnson (Inherent) noise can be modelled as an RMS voltage in series with the resistor: $$ e_{rms}\triangleq\sqrt{4kRT\Delta f} $$ where k is Boltzmann's constant, R is resistance, T is ...
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Square wave distortion at low frequencies, high-pass filtering, AC coupling

This is an update on my previous question. As Hearth suggeste, I changed to DC coupling on my scope. This is what I got: That's a clear change. Not a perfect square waves but I guess it is because of ...
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Square wave distortion on low frequencies

I have this old Soviet low frequency sine and square pulse generator "G3-36A". I ran into an interesting problem. When I try to generate square pulse under 100Hz I get a distorted wave. ...
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Matlab: using a small sample time for sine wave, makes the wave's frequency "accelerate"

I noticed that if I use a small sample time of DSP sine wave in matlab, the signal's frequency "accelerates": This is the signal with a proper sample time: But if I reduce the sample time ...
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2 answers
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How does a variable frequency drive reduce the energy consumption of a motor?

If the relationship between frequency and current is inversed as answered in this question, how does reducing the supply frequency reduce the energy consumption of a motor?
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Why do we need to install a variable frequency drive to reduce the energy consumption of a motor?

I have read that the power consumed by a motor under various load conditions is not constant according to the answers to this question. The electrical energy input changes according to the torque ...
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1 vote
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How does the electrical power from the output of a generator vary after a fault?

I know that after a sudden generation/load variation there is an imbalance between mechanical power and electrical power at the borders of generators which causes a frequency change according to the ...
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1 vote
2 answers
70 views

Convert a continuous voltage to a pulsed voltage

I have a continuous 5V voltage which I would like to switch ON/OFF at a certain frequency. The output should be between 2V - 5V, and the minimum duration between ON/OFF should be 1 ms. The control ...
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Is the power frequency characteristic of a network almost constant?

When a transient phenomenon happens in an electric power grid, the network reacts to this deviation with a power-frequency characteristic (MW/Hz). Reading the following paper ''Analysis and ...
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2 votes
1 answer
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Should the top torus of a Tesla coil be cut?

Dosen't the top load torus act like one turn coil in short circuit? Doesn't it "steal" (decrease) the energy transfer to the arc? As a load, it has an inductive reactance (1 turn solenoid.) ...
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Self regulating effect of loads for frequency control

How does power absorption from loads depend on frequency? I know that during a frequency deviation in power grid, there are primary reserves which control the frequency, but I know there is also the ...
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How are primary reserves activated for frequency control?

How are primary reserves activated for primary frequency control? In particular I have the following doubts: Is there a frequency threshold where each of them are automatically activated or they are ...
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2 votes
1 answer
72 views

Frequency reading 180 Hz on only one line to line measurement in three-phase backup 60 Hz LP gas powered generator in idle mode

I am running into an issue I don't understand why is happening. I have found how to "fix" it, but I am interested in ideas on what the actual source of the issue is Short version: I have a ...
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1 vote
2 answers
127 views

Square wave frequency multiplier

Where can I find a frequency multiplier circuit or IC that can multiply the frequency of a square wave or a sine wave by four? The input frequency can be from 100Hz to 1MHz, corresponding to an output ...
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what is the surplus-control of generation?

Reading the ''P1 – Policy 1: Load-Frequency Control and Performance'' document, published by UCTE in 2009 (it is available on internet for all) I noted that there are many contributions to Load-...
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1 vote
1 answer
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Derive open-loop frequency response from close-loop characteristic

How can I derive open-loop frequency response from close-loop characteristic of a real Operational transconductance amplifier?
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2 votes
3 answers
136 views

How is frequency measured in a power grid?

I know that voltage and current are measured with voltmeter and ammeter, but how is the frequenc measured in power grid applications? I know that a phase locked loop (PLL) can be used, but is this ...
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1 vote
2 answers
97 views

Why do we use low frequency with copper wires and high frequency with air and optical fibers?

The bandwidth of twisted pair copper wire is low. Why can low frequencies propagate longer distances through copper wires than high frequencies? On the other hand, high frequencies can propagate long ...
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How I can calculate the switching frequency of an SCR and replacing diode with SCR in boost converter? [closed]

I want to find the switching frequency of SCR. I want to use an SCR or a GTO thyristor so I can use a switching frequency up to 20 kHz, but as I am new so I am unable to find the SCR frequency from ...
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Converting square wave into a sine wave [closed]

I am trying to convert a 1 MHz square wave into a sine wave of the same frequency. What's the best way to achieve this?
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1 answer
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Comparator switching randomly

I cut a toroid in half, one half has unknown number of turns (50~80) which are fed to LM339 comparator which is pulled high by 500R to 3.3 V. simulate this circuit – Schematic created using ...
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50 Hz noise from mains plug even though it isn't connected to a power source

I am developing a front-end for a smart meter and I'm trying to measure the mains by using a power lead with the other end spliced to connect it to the front-end. I firstly powered the setup with a ...
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2 votes
2 answers
218 views

Media Independent Interface Signals

For the MII interface signals: I read in Wikipedia - MII on the Tx and Rx signals. But I am confused on why there are two clocks (for tx and rx)? Are the directions mentioned for transmitter signals ...
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6 votes
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Why does lower frequency require a lower voltage to drive a logic value?

Dynamic frequency scaling almost always appear in conjunction with dynamic voltage scaling, since lower frequencies require lower voltages for the digital circuit to yield correct results. The ...
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1 vote
1 answer
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How to calculate far field distance from an antenna

I understand the formula for calculating the far field distance from an antenna is: Distance = (2D^2)/λ Is the D in the above equation the length of the antenna under test (antenna under test is a ...
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Gate pulse PWM for IRF3205

I am trying to control DC motor with IRF3205, i cannot understand how much frequency pwm signal should be feed into gate of IRF3205.I want to operate 775sh 12V dc motor and the gate pwm frequency is ...
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1 answer
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32 kHz oscillator measurement

Thanks in advance for your help. I have the following circuit which is working fine. A 32 kHz oscillator NX3215SA (QUARZ SMD 32.768 kHz 3.2 x 1.5 mm) is simply connected to my MSP430F5438A on P7.0 and ...
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-1 votes
1 answer
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Is it possible to operate a Tesla coil at lower frequencies?

Tesla coils usually operate at a frequency level between 50 kHz to 1 MHz. What if we use a frequency between 60 to 100 Hz? Will it work? What will be the effect on the spark?
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Controlling BLDC motor using Arduino and esc

Reffering to this question Do all ESCs operate on this 1ms to 2ms range and 50Hz PWM or is this different for different ESCs, for example, one ESC for RC drones and another ESC for 5055 200kv BLDC ...
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1 vote
1 answer
56 views

Determining the impedance of an unknown component

If I have an antenna and I wish to measure its impedance. I have two impedance values, Z=125.52-j207.36Ohms and Z=8.14-j39.6Ohms, and I do not know which one is correct/ which one applies to this ...
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1 answer
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Can loads absorb more power than needed/requested?

I was designing the governor of a generator, implementing in Digsilent Powerfactory a 1 bus grid like that in the picture. The generator delivers 350 MW and the 3 loads withdraw respectively 25 MW, 25 ...
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3 votes
2 answers
498 views

Frequency behavior in the electric grid

Is the frequency behavior equal in very distant interconnected points of the grid? For example, if there is a sudden generation drop in Portugal, is the frequency behavior in Portugal exactly the same ...
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2 votes
1 answer
34 views

Miller effect and Open time circuit method

Let's say I have a common source amplifier with parasitic capacitances Cgs and Cgd (it can be any amplifier but I gave this concrete example to simplify my question). In order to approximate the 3db ...
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1 vote
3 answers
91 views

Will DC with a frequency have reactance?

I am getting mixed answers for the question. Quora says: There is no reactance! Xc = 1/(2 x pi x f x C), and since f=0, Xc = 0. The frequency is non-zero (for second and third picture,) though. Then ...
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0 votes
0 answers
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How to calculate natural frequency and zeta of underdamped, 2nd order system if only given experimental data?

How do I estimate the values of \$K\$, \$\zeta\$ and natural frequency, given the plot of unit step response of the system in time domain? I figured that at \$t = \infty\$, \$Y(t) = K\$ and I ...
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2 votes
3 answers
223 views

1 Hz ring oscillator not working

Inspired by this project I built a ring oscillator that outputs a 1 Hz signal. Using their formula, I decided to use 1K for R1 and R2, and 558 uF for C1. I used a CD4069UB CMOS inverter that has a ...
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1 vote
1 answer
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RFID read distance and frequency

In RFID (according to this source: https://blog.acdist.com/understanding-rfid-and-rfid-operating-ranges) there are: Low Frequency RFID: has the shortest read distance, about 10 centimeters between ...
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-1 votes
1 answer
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Experiencing issues with VHDL Code ModelSim: Wave Generation

I'm working on this project where I'm basically supposed to generate square wave (and other types of wave) using VHDL. The time period can be adjusted to either increase or decrease its frequency, and ...
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4 votes
5 answers
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UHF Colpitts Oscillator in Class C mode problem using Harmonic multiple

I want to increase the frequency of the crystal oscillator oscillating at 25MHz frequency. For this, I added an LC tank circuit to the collector in parallel with each other. I experimented to see if ...
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1 answer
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How to get RMS voltage and frequency from datapoints read from an ADC?

I have an ADC that samples 4000 times per second or 0.25 ms interval per sample. I would like to extract the RMS and frequency value of the signal being read. How do oscilloscopes and multimeters do ...
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1 vote
2 answers
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Loudspeaker alignment graph

Hopefully a simple question. I was wondering what the blue line in this graph represents. This is looking at loudspeaker modelling. The red line is obviously the frequency response as loudspeakers are ...
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2 votes
2 answers
128 views

Which theory do oscilloscopes or multimeters follow to measure RMS value?

For calculating RMS value , what I have found so far is that samples of a full cycle are taken then the ADC values are used to calculate RMS. Thus the RMS value stays independent of signal frequency. ...
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0 answers
157 views

Signal multiplier circuit using op amp concepts

Design a circuit that from two sinusoidal inputs generates the output \$s(t) = \sin(2π f_1 t) \times \sin(2π f_2 t)\$, where \$f_1\$ and \$f_2\$ are two distinct frequencies between 1 kHz and 10 kHz. ...
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