Impedance vs frequency graph

Impedance vs frequency graph

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impedance vs frequency graph

It only takes a minute to sign up. I thought that at the series resonant frequency of a piezoelectric oscillator the impedance of the crystal would be the lowest, and at the parallel resonant frequency the impedance would be the highest.

This picture would suggest so:. Clearly at series resonance, the impedance spikes low, and at parallel resonance the impedance spikes high. In the first one, apparently positive y-axis indicates inductive reactance, and negative y-axis indicates capacitive reactance.

I get the series resonant point: It is the one with the smallest absolute value. But why is the parallel resonant point at somewhere between 0 and the tip of the spike?

Shouldn't it be at the tip where the impedance is the highest? And what is "antiresonance"? The second picture I find equally confusing. It again seems to plot the absolute value of the impedance. Here the series and parallel points are the lowest and highest, as I would expect, but only in the center region!

Clearly if we go to the left, the curve goes up again, indicating there is a frequency for which the impedance of the crystal is higher. And likewise, if we go to the right, it would seem there is a point with a lower impedance.

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So why aren't the resonant points somewhere on the higher and lower frequencies? Or is there something I've completely misunderstood about resonance? On the left, there is an oscillator with the crystal in series mode.

The output of the amplifier is connected to the input through the crystal. As the series mode crystal has the smallest impedance at the series frequency, this is the frequency that is filtered from noise by the crystal and fed back to the amplifier input, and therefore the oscillator oscillates at this frequency. This is how I would imagine it to work, but according to the graphs, there should be other frequencies higher that can pass the crystal easier.

So why doesn't the oscillator oscillate at these frequencies? The same question applies for the parallel oscillator, except this time the impedance is highest for the desired frequency, and it is therefore the one being fed into the amp, with the other frequencies being directed to ground as the impedance is very low for these frequencies.

The vertical axis is purely impedance and the parallel impedance coincides with the peak impedance. Adding more parallel capacitance lowers that high-impedance point. Look at the X-scale - everything happens over a few hertz so some graphs seen on the internet are downright misleading because they don't tell you that what they show is just the X-axis in a small range of a few hertz.

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The parallel resonance is the peak of the magnitude BUT it doesn't have a defined impedance angle unlike series resonance.Documentation Help Center.

This tool can also be activated from the Powergui block dialog box by selecting Impedance vs Frequency Measurement. For example:. Lists the Impedance Measurement blocks of the model. Select the blocks for which you want to obtain the frequency response. Use the CTRL key to select several impedances to be displayed on the same plot.

Specify the frequency vector, in hertz Hz. The default is logspace 0,3, If selected, data are saved in a variable in the workspace. The name of the variable is defined by the Workspace variable name parameter. The complex impedances are saved in an array together with the corresponding frequencies.

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Frequency is saved in column 1 and impedances are saved in the next columns. Default is unselected. Click to initially display the impedance versus frequency measurement and, if the Save data when updated check box is selected, save the data to your workspace.

Click to start the impedance versus frequency measurement again and display results after multiple runs of your model.

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Search MathWorks. Off-Canvas Navigation Menu Toggle. Dialog Box. Measurement Lists the Impedance Measurement blocks of the model. Range Hz Specify the frequency vector, in hertz Hz. Grid If selected, a grid is displayed for the two plots. Save data when updated If selected, data are saved in a variable in the workspace.

Select a Web Site Choose a web site to get translated content where available and see local events and offers. Select web site.Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied. The term complex impedance may be used interchangeably. Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of a sinusoidal voltage between its terminals to the complex representation of the current flowing through it.

Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phaseunlike resistance, which has only magnitude. When a circuit is driven with direct current DCthere is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle. The notion of impedance is useful for performing AC analysis of electrical networks, because it allows relating sinusoidal voltages and currents by a simple linear law.

In multiple port networks, the two-terminal definition of impedance is inadequate, but the complex voltages at the ports and the currents flowing through them are still linearly related by the impedance matrix.

However, cartesian complex number representation is often more powerful for circuit analysis purposes. The reciprocal of impedance is admittancewhose SI unit is the siemensformerly called mho. Instruments used to measure the electrical impedance are called impedance analyzers. The term impedance was coined by Oliver Heaviside in July In addition to resistance as seen in DC circuits, impedance in AC circuits includes the effects of the induction of voltages in conductors by the magnetic fields inductanceand the electrostatic storage of charge induced by voltages between conductors capacitance.

The impedance caused by these two effects is collectively referred to as reactance and forms the imaginary part of complex impedance whereas resistance forms the real part. Impedance is defined as the frequency domain ratio of the voltage to the current.


For a sinusoidal current or voltage input, the polar form of the complex impedance relates the amplitude and phase of the voltage and current. In particular:. The impedance of a two-terminal circuit element is represented as a complex quantity Z. In Cartesian formimpedance is defined as. Where it is needed to add or subtract impedances, the cartesian form is more convenient; but when quantities are multiplied or divided, the calculation becomes simpler if the polar form is used.

A circuit calculation, such as finding the total impedance of two impedances in parallel, may require conversion between forms several times during the calculation. Conversion between the forms follows the normal conversion rules of complex numbers. The magnitude equation is the familiar Ohm's law applied to the voltage and current amplitudes, while the second equation defines the phase relationship. This representation using complex exponentials may be justified by noting that by Euler's formula :.

The real-valued sinusoidal function representing either voltage or current may be broken into two complex-valued functions.

By the principle of superpositionwe may analyse the behaviour of the sinusoid on the left-hand side by analysing the behaviour of the two complex terms on the right-hand side. Given the symmetry, we only need to perform the analysis for one right-hand term. The results are identical for the other.

At the end of any calculation, we may return to real-valued sinusoids by further noting that. The meaning of electrical impedance can be understood by substituting it into Ohm's law.

A phasor is represented by a constant complex number, usually expressed in exponential form, representing the complex amplitude magnitude and phase of a sinusoidal function of time. Phasors are used by electrical engineers to simplify computations involving sinusoids, where they can often reduce a differential equation problem to an algebraic one. The impedance of a circuit element can be defined as the ratio of the phasor voltage across the element to the phasor current through the element, as determined by the relative amplitudes and phases of the voltage and current.

The impedance of an ideal resistor is purely real and is called resistive impedance :. Ideal inductors and capacitors have a purely imaginary reactive impedance :. In both cases, for an applied sinusoidal voltage, the resulting current is also sinusoidal, but in quadrature90 degrees out of phase with the voltage.Sign in to comment. Sign in to answer this question. Unable to complete the action because of changes made to the page. Reload the page to see its updated state.

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What are impedance/ ESR frequency characteristics in capacitors?

Support Answers MathWorks. Search MathWorks. MathWorks Answers Support. Open Mobile Search. Trial software. You are now following this question You will see updates in your activity feed. You may receive emails, depending on your notification preferences. Impedance vs Frequency Plot. Alec Reed on 31 Jul Vote 0. Edited: madhan ravi on 12 Nov Accepted Answer: David John. I am experienced with Matlab but still learning Simulink. I am trying to use a lumped element model to simulate a ferrite bead, but struggling to set up the simulation.

The electrical circuit is just a Parallel RLC connection and a in line resistance, created from sim space blocks See Image 1. I want run a frequency sweep to show the impedance vs frequency see image 2 I have tried Using the impedance measurement and the DSP tool box spectrum analyzer but have not been able to connect any measurement tools to my circuit.

How can I run a frequency sweep within a Simulink simulation and output a impedance vs frequency bode plot? Image 1. Thanks for the help!


Accepted Answer. David John on 7 Nov Cancel Copy to Clipboard. Simscape solves in the time-domain, so you cannot directly do a frequency sweep.

You can, however, linearize the model and then perform a Bode analysis. Please see for an example of this approach. More Answers 0.Latest Projects Education. Homework Help Plotting input impedance vs frequency.

Home Forums Education Homework Help. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Plotting input impedance vs frequency. Thread starter jegues Start date Oct 31, Search Forums New Posts. Thread Starter jegues Joined Sep 13, See figure attached for problem statement.

We've been studying RC, LC and RLC circuits in class, but never have we discussed "resonance", or plotting things such as input impedance versus frequency, hence my confusion. I simply plugged in the values for R, L and C given into our equation for Zin. It says to use the logarthimic unit for impedance but I'm not entirely sure how to do that. If that equation is indeed what I am being asked to plot could anyone be so kind as to post a matlab graph?

I don't know why they ask for it using matlab, the students were not provided with it nor do we have any access to it. Is there any other tools out there that I can use to graph this?

What Speaker Impedance Means and Why It Matters

Thanks again! Scroll to continue with content. The instructions say you can plot the graph manually, The Log statement involves the graph type, e. A programmable calculator HP or TI will be able to run that equation for different inputs quite readily.

Last edited: Oct 31, The Electrician Joined Oct 9, 2,The chief electrical characteristic of a dynamic loudspeaker 's driver is its electrical impedance as a function of frequency. It can be visualized by plotting it as a graphcalled the impedance curve.

The most common driver type is an electro-mechanical transducer using a voice coil rigidly connected to a diaphragm generally a cone. Other types have similar connections, though differing in detail, between their acoustical environment and their electrical properties. The voice coil in moving coil drivers is suspended in a magnetic field provided by the loudspeaker magnet structure. As electric current flows through the voice coil from an electronic amplifierthe magnetic field created by the coil reacts against the magnet's fixed field and moves the voice coil and so the cone.

Alternating current will move the cone back and forth. The moving system of the loudspeaker including the cone, cone suspension, spider and the voice coil has a certain mass and compliance. This is most commonly likened to a simple mass suspended by a spring that has a certain resonant frequency at which the system will vibrate most freely. This frequency is known as the "free-space resonance" of the speaker and is designated by F s. At this frequency, since the voice coil is vibrating with the maximum peak-to-peak amplitude and velocitythe back-emf generated by coil motion in a magnetic field is also at its maximum.

This causes the effective electrical impedance of the speaker to be at its maximum at F sshown as Z max in the graph. For frequencies just below resonance, the impedance rises rapidly as the frequency approaches F s and is inductive in nature. At resonance, the impedance is purely resistive and beyond it—as the impedance drops—it behaves capacitively. The impedance reaches a minimum value Z min at some frequency where the behaviour is fairly but not perfectly resistive over some range.

A speaker's rated or nominal impedance Z nom is derived from this Z min value see below. Beyond the Z min point the impedance is again largely inductive and continues to rise gradually. The variation in loudspeaker impedance is a consideration in audio amplifier design. Among other things, amplifiers designed to cope with such variations are more reliable.

There are two main factors to consider when matching a speaker to an amplifier. This is the minimum value in the impedance vs. Minimum impedance is significant because the lower the impedance, the higher the current must be at the same drive voltage.

The output devices of an amplifier are rated for a certain maximum current level, and when this is exceeded the device s sometimes, more or less promptly, fail. Due to the reactive nature of a speaker's impedance over the audio band frequencies, giving a speaker a single value for 'impedance' rating is in principle impossible, as one may surmise from the impedance vs.

The nominal impedance of a loudspeaker is a convenient, single number reference that loosely describes the impedance value of the loudspeaker over a majority of the audio band. A speaker's nominal impedance is defined as:. The graph shows the impedance curve of a single loudspeaker driver in free-air unmounted in any type of enclosure. A home hi-fi loudspeaker system typically consists of two or more drivers, an electrical crossover network to divide the signal by frequency band and route them appropriately to the drivers, and an enclosure that all these components are mounted in.

The impedance curve of such a system can be very complex, and the simple formula above does not as easily apply. The nominal impedance rating of consumer loudspeakers systems can aid in choosing the correct loudspeaker for a given amplifier or vice versa.

impedance vs frequency graph

If a home hi-fi amplifier specifies 8 ohm or greater loadscare should be taken that loudspeakers with a lower impedance are not used, lest the amplifier be required to produce more current than it was designed to handle. Using a 4 ohm loudspeaker system on an amplifier specifying 8 ohms or greater could lead to amplifier failure.Properties of standard coaxial type cables have been very much standardized for many years. Unless you buy rogue stock from a supplier, if you abide by the manufacturer's application guidelines, there should not be any surprises.

Do not make a bend of smaller recommended radius, do not expose the cable to excess temperatures, vibration, mechanical stress, or chemicals. Be absolutely certain to attach the coaxial cable into a properly designed connector, printed circuit board, or other type termination, paying careful attention to insulation and dielectric strip lengths, solder temperatures and dwell times, and shielding preparation.

Do all that, and you will be assured a long lifetime from your cable system. Check this out - someone referenced this page on Wikipedia. Note that attenuation values are given at MHz, but can - and do - often have significantly different values at other frequencies.

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Always check with a coaxial cable vendor for values specific to the type you plan to use. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

impedance vs frequency graph


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