Does Anyone Ever Squelch To Get A Better Impedance Measurement?

This seems to work on SPICE.

Bret Cahill

Then gently remove the higher frequency, and wash the wound with warm soapy water, and apply a clean bandage.

That seems fairly non-obvious to me. how is a low frequency better for measuring the impedance of a twisted pair?

I'm tring to picture a squelch switching at some high frequency and failing. Perhaps you mean something different?

Somehow "inductance" got left out.

The squelch working at a high frequency.

Whenever the absolute value of the 2nd derivative of current, or for that matter, the absolute value of the 1st derivative of voltage, is above a threshold value both voltage and current signals are set to zero.

Bret Cahill

That is evident. where was it supposed to go?

That sounds like a great way to inject noise at a yet higher frequency into an otherwise working system, I can't immagine whay you'd want to do that.

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Would that be true if the squelching was digital?

To get the inductance.

Bret Cahill

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Yes, I squelch from time to time, esp when I read my electricity bill.

Hardy

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I've obviously come in late here in comp.dsp, so there may be something I missed that would make this rational. As it stands with me, the question is ludicrous. You are evidently attempting to make an electrical measurement by blinding your instruments to both voltage and current. Can you explain how that's assumed to work?

Jerry

-- Engineering is the art of making what you want from things you can get.

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You are only shutting them down when their eyes could wander.

Bret Cahill

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How does that get you the information you want?

Jerry

-- Engineering is the art of making what you want from things you can get.

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Just as you don't need all the frequencies and you don't need all of the cycle of any one frequency either.

You can select just the parts of the cycle where the noise is lowest or, in this case, the current bleeding off through resistances and capacitances is lowest.

It would be surprising if this was the first time this was done in electronics.

Bret Cahill

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Whatever you need or don't, how does squelching provide more information?

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You sample the data, so instead of squelching the signal, why not simply ignore the samples you don't want? In any case, the current will be lowest when the voltage Resistance) or its derivative (capacitance) is.

Jerry

-- Engineering is the art of making what you want from things you can get.

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Well it provides _less wrong_ information, same as low pass filtering for inductance.

Is that really any different than squelching?

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One effective way to squelch for inductance is to integrate current to charge and integrate voltage a couple of times. Then discard the greater part of the cycle that isn't near the maximum charge or volts sec sec.

The low pass effect from the integration seems to help.

Bret Cahill