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Hello team,

Trying to understand a good method of measuring the inductance - lets say around 110uH - of a coil.

Is the L/C method the best? Is there any direct method of measuring the L?

Also, for L/C circuit where can I find a 1% accurate capacitor around 50 or 100 pf? If this LC method is the best, then I will make a jig where the capacitor its already embedded and I only add the coil.

Cheers!


Luis CT2FZI

I use XJW01 digital bridge 0.3% for measure R, L, C

Measure C: 0,1 pF–10000 mF
Measure L: 0,01 uH–1000 H
Measure R: 0,0002 Ом–9,999 МОм

If calibrate on good calibration standarts allow get better result

Use for measure 4 wire line

It show very good result

Luis,
Most commercial LCR meters for less than $200 only measure inductance or capacitance below 1 MHz. Manufacturers specify the values of their inductors or capacitors at a specific test frequency, also usually below 1 MHz. The NanoVNA can give measurements to at least 5% for inductors and capacitors using fairly simple fixtures such as the sma-banana plug adapter in the attached photos.

The attachments shows a Cambion 22 uH inductor being measured. From 50 kHz - 1 MHz the measured values vary from 22 uH by 0.5 uH.

If you attempt to measure the inductance or capacitance of the components at higher frequencies then the lead length, self-resonant frequency, and fixture all start to come into play with your measurements.

- Herb

What settings did you use to get these measurements ?

Tnx, Dick, W1KSZ
________________________________
From: [email protected] <[email protected]> on behalf of hwalker <herbwalker2476@...>
Sent: Sunday, April 26, 2020 8:33 AM
To: [email protected] <[email protected]>
Subject: Re: [nanovna-users] [Measuring] What is your favourite method of measuring inductance in a coil?

Luis,
Most commercial LCR meters for less than $200 only measure inductance or capacitance below 1 MHz. Manufacturers specify the values of their inductors or capacitors at a specific test frequency, also usually below 1 MHz. The NanoVNA can give measurements to at least 5% for inductors and capacitors using fairly simple fixtures such as the sma-banana plug adapter in the attached photos.

The attachments shows a Cambion 22 uH inductor being measured. From 50 kHz - 1 MHz the measured values vary from 22 uH by 0.5 uH.

If you attempt to measure the inductance or capacitance of the components at higher frequencies then the lead length, self-resonant frequency, and fixture all start to come into play with your measurements.

- Herb

Dick 9:58am #12913
What settings did you use to get these measurements ?
=====================================
Dick,
No special settings. Just turned off the CH1 traces, set the frequency sweep from 50k - 1M, and read the inductance on CH0 from the smith chart readout as shown in the screenshot.

- Herb

There must be something else as I cannot reproduce your results.
Now, I am using a NanoVNA-F, but I can't see where that matters.
Trying to measure a 10 mH RF Choke, display bounces around from
190pH to 600pH.

Guess it's back to my LCR Meter, at least I can get that to work.

Tnx for the reply,

73, Dick, W1KSZ
________________________________
From: [email protected] <[email protected]> on behalf of hwalker <herbwalker2476@...>
Sent: Sunday, April 26, 2020 10:34 AM
To: [email protected] <[email protected]>
Subject: Re: [nanovna-users] [Measuring] What is your favourite method of measuring inductance in a coil?

Dick 9:58am #12913
What settings did you use to get these measurements ?
=====================================
Dick,
No special settings. Just turned off the CH1 traces, set the frequency sweep from 50k - 1M, and read the inductance on CH0 from the smith chart readout as shown in the screenshot.

- Herb

Hi Herb,

Good thing those banana adapters are OK for DC, I will opt for that method.

I will need to measure some coils for end fed antennas and a coil in a
trap, lets see what I can do. At 1MHz I think I will be very happy with 5%
or less! :)




*73 de Luís, CT2FZI*

*QRV @ 145.300 MHz | **CQ0VMST (VHF REP Monsanto)*
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On Sun, Apr 26, 2020 at 10:44 AM, Dick wrote:

There must be something else as I cannot reproduce your results.
...... Trying to measure a 10 mH RF Choke, display bounces around from 190pH to 600pH. ..
==============================
Dick,
Sorry for the delayed response. I work at rf frequencies that only requires micro-henries for suppression and steering and haven't testing any chokes in the milli-henry range. It took me a while to hunt down something in my parts bin.

I found an old J. Miller 16mH choke which was too large to fit in the sma-banana plug, so I had to use micro-clips (see attachment). I don't know what test frequency manufacturers specify their chokes at but the J. Miller choke quickly became capacitive with high impedance above 200 kHz. I limited my sweep to 30 kHz-200kHz for testing. In that range values between 16.9 - 22.9 mH were measured. At 50 kHz the impedance of the choke measured closest to the NanoVNA system impedance (50 ohms) and the coil value was 16.7 mH (see screen shot attachment). If I was sorting components I would have used that value.

I also found a J. Miller 60mH choke but it wouldn't measure correctly and close examination with a magnifying glass showed that one of the wires had broken off its terminal. Tagged and marked for repair.

- Herb

On Sun, Apr 26, 2020 at 07:28 AM, CT2FZI wrote:

Also, for L/C circuit where can I find a 1% accurate capacitor around 50 or 100 pf?

I have several CDE silver mica capacitors I ordered from Mouser, and have several more on back order. I bought leadless surface mount capacitors, but they also have leaded varieties. The ones I bought are 1 percent tolerance, but some are also available in 0.5 percent tolerance, or even 0.1 pf tolerance. That's probably overkill (also expensive). The 1 percent caps I bought were just under 5 dollars each, if I remember correctly. If you can live with 5 percent tolerance, the price is probably half that, but I figured 5 bucks for a Hi-Q, tight tolerance capacitor I can use for a "standard" is cheap.

On Sun, Apr 26, 2020 at 01:27 PM, hwalker wrote:

Dick wrote:
There must be something else as I cannot reproduce your results.
...... Trying to measure a 10 mH RF Choke, display bounces around from 190pH to 600pH. ..

hwalker replied:
...I don't know what test frequency manufacturers specify their chokes at but the J. Miller choke quickly became capacitive with high impedance above 200 kHz. I limited my sweep to 30 kHz-200kHz for testing. In that range values between 16.9 - 22.9 mH were measured. ....
=========================================

An article titled "Measuring mH inductors with the VNWA" at also seems to indicate that large value (mH) inductors quickly go parallel resonant with with high impedance above 100 kHz making accurate measurements with a 50 ohm NanoVNA difficult.

If you are trying to determine how much impedance the 10 mH inductor will give you at and above its parallel resonant frequency, then you should switch to the series S21-method to get a more precise number. If you are just trying to verify its marked value then I would limit testing to below 200 kHz. Limiting the NanoVNA's band width below 1 kHz using DiSlord's beta firmware (not applicable to NanoVNA-F) also helped to stabilize readings.

The VNWA has been around for a few years now. I had been on the lookout for one before the NanoVNA came on the scene but never came across a deal that didn't break my budget. Many articles, fixtures, and measurement techniques for the VNWA can be applied to the NanoVNA. Kurt Poulsen OZ7OU, a member of this group, has been a frequent contributor to the VNWA over the years and has freely passed on some of his knowledge here.

- Herb