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Need to find LC impedance of the LC network - Reg

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prakashvenugopal

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Hi all,

I am using a LC network. For measurement of Inductance (L) and Capacitor (C), i am using LCR meter to measure the L & C. I have to measure Impedance of LC network using any meter. Is there any meter to measure the impedance of the LC network. Kindly let us know.

Regards,
V. Prakash
 

Hi,

Thanks for the reply. my LC network frequency is 30 khz. will we able to check the impedance of this LC network using this device? kindly let us know.

Regards,
V.Prakash
 

* The coil has a certain amount of ohmic resistance which you can measure with any VOM or DMM. It isn't necessarily crucial to know its value since the resonant LC frequency is based on L & C values as seen in the formula, however the formula contains no variable for R.

* A leaky capacitor has some unknown ohmic resistance, measurable with a VOM. A capacitor might have excessive ESR which cannot be detected with a VOM but can be observed via its altered operating characteristics.

* A general method to measure your AC reactive impedance... Feed it a sine waveform, measure amplitude. Insert a potentiometer (variable resistor) in the wire and dial it until amplitude drops to half the previous level. Then potentiometer resistance matches LC impedance at that frequency. For this to work properly, you must determine which is the sensible place to install the resistance, whether in series or in parallel, between signal and your LC network or following your network, etc.

As for 30 kHz, an inexpensive VOM or DMM probably won't respond properly to it.
 
Hi all,

I am using a LC network. For measurement of Inductance (L) and Capacitor (C), i am using LCR meter to measure the L & C. I have to measure Impedance of LC network using any meter. Is there any meter to measure the impedance of the LC network. Kindly let us know.

Regards,
V. Prakash
What is the manufacturer and model number of your LCR meter?
 

Hi

LCR meter Model: Sigma MTQ4070.
In this meter, no option to measure the impedance of the LC network. If anyother model meter to measure LC impedance is highly useful to me.

Regards,
V.Prakash
 

Hi

LCR meter Model: Sigma MTQ4070.
In this meter, no option to measure the impedance of the LC network. If anyother model meter to measure LC impedance is highly useful to me.

Regards,
V.Prakash
There are many meters that can do what you want, but they may cost more than your budget will allow.


Is this a school project, or are you working for a company? How much money can you spend on a new meter?
 
Hi,

It is for industrial use only. can spend upto 10,000 rs for LC network impedance measurement meter. kindly let us know if you used it.

Regards,
V.Prakash
 

Almost always when you make an LC arrangement you're interested in its resonant frequency, whether it's on target or needs further tailoring. Also its Q.

These give clues to how it should respond in your circuit, at your Volt and Ampere levels.

So while you're going to the effort of testing impedance, you might as well go to a little more effort and discover the full picture.

Impedance is not measured directly. To observe such parameters, the typical method is to apply various frequencies and see what happens.
Does the curve show a sharp peak at resonance? Or a barely noticeable bump? Or a trough? Or multiple peaks?
Is it resonant at a higher frequency than your desired frequency? Or a lower frequency? Do you need to change L or C value?
 
It would be helpful to know the LC network topology. A LCR meter measures complex impedance at a specific frequency, represented by an equivalent circuit of your choice, e.g. L+Rs, C+Rs, etc. Depending on the network topology, multiple frequency points are necessary to identify the network.
 
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