application of signals

[bhuvaneshnick]

All basic signals have specific purpose

impulse -used to get frequency response of system

step- used to get time response of system and it also used to extract some portion of signal

signum-?

ramp-?

my i knowthat use or application of above two signals.Thank you in advance.

 

[Tony Stewart]

signum ... or Sine wave represents a single frequency which may be suitable as a carrier for power, or signals in communication channels or just a pilot tone for testing.

ramp ... or an integrated Step, can represent a constant current into a large capacitor or battery until it stops or levels off, if the ramp is a voltage. ....If you apply a small battery to a large transformer or iron core inductor, the current will ramp until the core saturates. Smaller cores result in faster ramp current. Then when you open the current, you get an impulse voltage. (zap)

It is useful to know how to realize and convert an impulse into any other signal such as Integral to Step and 2nd integral to Ramp and Sine wave into a Resonant Circuit.

 

[bhuvaneshnick]

signum ... or Sine wave represents a single frequency

i have not crossed fourier series . Does fourier series of signum gives only one frequency ?

ramp ... or an integrated Step

is integrating step we get ramp?

can represent a constant current into a large capacitor or battery until it stops or levels off

step alone give constant current not ramp(it gives linearly increasing current )

If you apply a small battery to a large transformer or iron core inductor, the current will ramp until the core saturates. Smaller cores result in faster ramp current.

i cant understand this

It is useful to know how to realize and convert an impulse into any other signal such as Integral to Step and 2nd integral to Ramp and Sine wave into a Resonant Circuit.

i hear that any signal can be represented as weighted sum of impulse.is that what you saying in this line?

 

[KeepItSimpleStupid]

If you apply a small battery to a large transformer or iron core inductor, the current will ramp until the core saturates. Smaller cores result in faster ramp current.

i cant understand this

The current in an inductor can't change instantaneously. Look at the eqn for the voltage across an inductor. It has di/dt in it. di/dt can't be infinity.

 

[Jugurtha]

Hello,

The current in an inductor can't change instantaneously. Look at the eqn for the voltage across an inductor. It has di/dt in it. di/dt can't be infinity.

The way I understand it, the voltage across an inductor is L(di/dt). di/dt can't be infinity, but it "tends" to infinity if dt tends to zero 0 (as in opening a switch and breaking the current loop, the current drops crazy fast (the time it takes to open a switch)). We have a voltage spike (hence flyback/free-wheeling diodes when working with inductive loads for the energy stored in the magnetic field to be converted gradually (oversimplification)). So, granted, it's not "technically" infinity and "instantaneous" (the same technicality that makes it that we can't really say that a capacitof is fully charged), but it's still rather important.

At least, that's the way I understand it.

 

[KeepItSimpleStupid]

Back in my college days, those two principles of 1) the current can't change instantaneously in an inductor and the 2) the voltage can't change instantaneously in a capacitor were more important than the equations even though that's what the equations were trying to say.

One also has to learn to neglect things when they are not important and consider them when they are. I can say to you that vibration introduces currents in conductors and you might say I was nuts. I could also put probes on a piece of paper and give you a conductance that would depend on the amount of water the paper absorbed. I had to tape down wires to avoid measurement errors due to vibration or (a conductor moving in the Earth's magnetic field). Dissimilar mets at thermocouple half junctions with varying temperatures screw up the thermocouple measurements.

 

[Jugurtha]

One also has to learn to neglect things when they are not important and consider them when they are.

Oooh yeah, your comment makes a lot of sense for different reasons. These days, I'm brushing up my Physics and Maths and among the books I'm reading, there are Soviet Era books (MIR Publishers). Some of them I have from my older brothers and sisters, but anyway, I found it fascinating that there are many things Soviet books stressed from the beginning that I haven't found in books written elsewhere where they just take things for granted.

For instance, Belikov's "General Approach to Solving Physics Problems" introduces interactions (strong, electromagnetic, weak, gravitational) as soon as page 12. A lot of other books also introduce interactions and concepts of physics (example: Irodov's "Fundamental Laws of Mechanics" , Landau & Lifschitz's books, or Matveev's "Electricity and Magnetism"). You don't find this in most books.

My point is that they put a lot of stress on the fact that to study a problem, you can't take *everything* into account and you must simplify, sometimes idealize things, etc., in order to be able to solve the problem.. It'd be insanely hard not to. Something such as Newton's second law is introduced in a complete different manner, talking about the conditions of applicability of the law (inertial reference frame, etc). My courses in college were similar (momentum was introduced not as it's introduced in most books written in English 'mv', but included the "speed of light in vaccum" part (most books don't, and if they do, don't mention "in vaccum"), and then we're told that the particle moves much slower than photons, and the mass is constant (again, taken for granted in many books), so we can extirpate the mass from the derivation of the momentum, and the fraction of squared velociy/c is approximated to 0, which gives m.γ . ).

They are rigorous enough to tell you that sometimes you must not be too rigorous. Which is different from not being aware of the latitude you're taking simplifying a problem. This is a similar approach to the saying (I think Picasso's) :"Learn the rules like a pro so you can break them like an artist". These books are *soooooo* good, they make the other 99.99% of the books appear as "X for dummies".