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how to measure inductance?

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chunlee

Advanced Member level 4
how to measure inductance

Can somebody tell which instruments are needed to measure the inductance and Q of a spiral inductor and active inductor? how to measure it?

Thanks.

Best regards,
chunlee

measuring inductance

you can use a network analyzer. You can determine the Q value from group delay obtained from the network analyzer.

hitechsolutions

hitechsolutions

Points: 2
how to measure inductance of coil

Hi,

latest technology of Fluke Instruments (the Digital Multi Meter that is)
can measure capacitance, charges (in coulombs) and inductances

Hey, I use Fluke!

hitechsolutions

hitechsolutions

Points: 2
inductor measurement

One of the easiest ways of measuring L is to build an LC oscillator with known capacitance, measure frequency and calculate the inductance from the common LC-tank equation: ω=1/√LC --> L=1/ω²C, where ω=2Πf ..
See circuit below ..
Regards,
IanP

Points: 2

Points: 2

arifsobhan

Points: 2
measure inductance of a coil

Q meter is mostly used for the measurement of inductance and Q of circuit

how to measure inductance of a coil

measure inductance

hi boy,

can u pls tell how to measure inductance and Q using network analyzer?
or send me some document about it?

Thanks.

measuring inductance of a coil

You can build an easy microcontroller based L/C meter
here is it..

I hope it helped.

covcst

V
Points: 2

covcst

Points: 2
inductance measurement method

chunlee said:
hi boy,

can u pls tell how to measure inductance and Q using network analyzer?
or send me some document about it?

Thanks.

The NA is a rather expencive & very rare instrument. You'd better try some LC-Q meter which are much easier to find.

how to measure inductor

VNA may measure L (and or C) but it's poorly accurate, especially on the Q determination.

Qmeter, when used in conjunction with Standard inductances is the most accurate instrument.
Qmeter give L, Q, SRF.

measure inductance coil

sergio mariotti said:
VNA may measure L (and or C) but it's poorly accurate, especially on the Q determination.

Qmeter, when used in conjunction with Standard inductances is the most accurate instrument.
Qmeter give L, Q, SRF.

Why did you comment so ? When you short circuit of an inductance, you'll get "very accurately" R and X so then to find inductance value and its associated Q factor are not difficult.

Because in RF region, inductances and capacitances are not flat responded and in my opinion an inductance or capacitance should be measured at the frequency of operation (or closer to )

But essentially, Q factor measurement equipments can not reach very high frequencies and their results are therefore not indicative.

how to measure an inductor

hi everyone,

I'm intend to measure my inductor on wafer at frequency around 2.4GHz. So i think the VNA is suitable for me. Can someone pls briefly tell me the procedure to characterize the inductor? (spiral and active inductor)

Thanks.

fluke inductance meter

BigBoss said:
sergio mariotti said:
VNA may measure L (and or C) but it's poorly accurate, especially on the Q determination.

Qmeter, when used in conjunction with Standard inductances is the most accurate instrument.
Qmeter give L, Q, SRF.

Why did you comment so ? When you short circuit of an inductance, you'll get "very accurately" R and X so then to find inductance value and its associated Q factor are not difficult.

Because in RF region, inductances and capacitances are not flat responded and in my opinion an inductance or capacitance should be measured at the frequency of operation (or closer to )
I try to answer BigBoss and chunlee both.

The accuracy of VNA measurement is set mainly by Standards, that are usually very accurate jewels, and often the residual accuracy is of the order of +/-0.02...0.05 (number! not dB). But, when you try to measure very reactive devices (i.e. near to the boundry of the Smith Chart) , a small uncertainty like +/-0.02 , will became a large uncertainty on Q determination . I don't provide here the formulation, see Agilent AN-95.

Qmeter has a different principle of operation. It read the resonant extravoltage.

But if the practical measurement needs are on wafer, there is no choices. Both VNA and on-wafer Standards are required.

Answering chunlee, set the VNA to display a Smith Chart on the screen. If necessary set marker parameters to display R+jX. I know that is possible on Agilent 87xx and 8510. Q=|X/R|

Since the accuracy on-wafer will be not very high, my suggestion is that the user should propagate the uncertainty equation to give an evaluation of the instrumental uncertainty.
Agilent provide a free and useful MS Excel speadsheet to evaluate uncertainty. look for "VNAUncert"

measuring coil inductance

What is the best way for measuring the inductance of a small planar coil inductor (i.e. RFID tag) ?

Would it be OK to use the VNA method for this? i.e. connect both terminals of the coil to a 50 Ohm bnc connector and measure it that way?

OR

Is there a better suited method? i.e. involving a signal/function generator?

Regards

Cat

measure coil inductance

chunlee said:
hi everyone,

I'm intend to measure my inductor on wafer at frequency around 2.4GHz. So i think the VNA is suitable for me. Can someone pls briefly tell me the procedure to characterize the inductor? (spiral and active inductor)

Thanks.

After doing two ports S-parameter measurement, transform S-matrix into admittance (Y) matrix, you can calculate Q and L using:

Q=-Im[Y(1,)]/Re[Y(1,1)]

L=Im[1/Y(1,1)]/ω

I am not sure whether there is difference between the calibration procedure of passive inductors and active inductors.

Regards,

find inductance

Treat the inductance as a two-port network, and you can measure the s parameter,
and you can deduce the L from the S parameters.
Perhaps not accurate.

s parameter inductance

Hi,

To measure the inductance of a coil is the following method reasonable?

1. Connect coil to DC voltage supply and measure the current
2. Calculate the DC resistance
3. Connect coil to an AC voltage suuply with known voltage and frequency, measure the current.
4. Calculate the Impedance
5. Calculate Inductive Reactance using results from steps 2 and 4.
6. Calculate the Inductance using the result from step 5.

Would this be accurate?

Regards

Cat

how to find inductance

Hi all,
I got a problem when re-draw S-parameters after de-embedding procedure.
I used ADS to re-draw Smith chart of an on chip spiral inductor.

- 1st, I used GSG probe tip to measure spiral (DUT) not very high frequency (50MHz --> 10GHz). Here I got S_measured values.
- 2nd, I measured inductor test-fixture only (open standard). Here I got S-open values.

Since I got the S-parameters data, I used ADS to convert S into Y data (S_measured ==> Y_measured & S_open ==> Y_open).
Then, took: Y_mo = Y_measured - Y_open
Finally, Y_mo data were reconverted into S-parameters and plotted in Smith chart.
But in here, the Smith chart was not as I expected.
Please take a look at 2 pictures following:

Is there any body give me an advice? I really appreciate any your help.
Thank in advanced! ^_^

fluke inductance

Can you connect the same to a connector directly-both ends of the inductor and measure S11 to find L?

coil inductance measurement

The problem is lying at that you Ymo=Y_meas-Y_Open, after that, the Y you got still include 50 ohm (system impedance) in series. That is why it looks so strange.

Hope it help!

Laipi

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