**EMRFD Message Archive 7925**

MessageDateFromSubject7925 2012-11-13 03:53:52 pauldebono@rocket... an accurate L meter I am searching for a good L meter, that can measure low to very low RF inductances. The various kits and models around based on a PIC and the LM311, are not good enough. So are these commercial multimeter types.

I came across the M3 or M-Cubed LCZR meter, which Monty, N5ESE, has reviewed and compared with the top, industry standard, the Philips PM6303 LCR Meter (now made by Fluke). Unfortunately , this meter kit is no longer in production. See: http://www.n5ese.com/M3LCR_meter.htm

However, a Metacrawler search, came up with an updated version of this meter:

(It is in French, but their sales department have an English version of the manual.)

http://www.mwinstruments.com/MW1008/MW1008_f.html

Paul7926 2012-11-13 04:35:35 Gary, WB9JPS Re: an accurate L meter I use my N2PK VNA for really small L and C values. Since they are probably SMT anyway, I have a little fixture with SMA connectors on it and short microstrips to which I solder the parts. Then the parasitics are very low, and also realistic for practical installations as well. Resoluti7927 2012-11-13 06:10:43 Thomas S. Knutsen Re: an accurate L meter How would the LM311 based meters do if you connect an larger inductor in

series with the small?

Radiometer used that technique in an high accurate LC meter in the 1960's.

An 0.5�H or 1�H high Q inductor in series, and nulled with the meter may

increase the accuracy.

If you still need to increase the accuracy above that, then an network

analyzer may be the tool you need to measure the inductors.

73 de Thomas LA3PNA / AE5YS.

2012/11/13 pauldebono@rocketmail.com <pawlud@gmail.com>

> **--

>

>

> I am searching for a good L meter, that can measure low to very low RF

> inductances. The various kits and models around based on a PIC and the

> LM311, are not good enough. So are these commercial multimeter types.

>

> I came across the M3 or M-Cubed LCZR meter, which Monty, N5ESE, has

> reviewed and compared with the top, industry standard, the Philips PM6303

> LCR Meter (now made by Fluke). Unfortunately , this meter kit is no longer

> in production. See: http://www.n5ese.com/M3LCR_meter.htm

>

> However, a Metacrawler search, came up with an updated version of this

> meter:

> (It is in French, but their sales department have an English version of

> the manual.)

> http://www.mwinstruments.com/MW1008/MW1008_f.html

>

> Paul

>

>

>

Please avoid sending me Word or PowerPoint attachments.

See <http://www.gnu.org/philosophy/no-word-attachments.html>

PDF is an better alternative and there are always LaTeX!

[Non-text portions of this message have been removed]7928 2012-11-14 06:57:02 Ashhar Farhan Re: an accurate L meter The simple way is to make an ugly vfo, measure the frequency shift

with and without the inductor under test and calculate the inductance

as a function of frequency shift.

The frequency shift of relatively small inductor (compared to the

effective inductance of the oscillator) will be a linear function of

the additional inductance. This is beacuse the differential of square

root is linear..

I have measured inductances as low as 5nH with this. The precision is

limited by precision and accuracy of the frequency counter and short

term stability of the vfo.

Add the unknown inductance between the coil and the ground. Measure

the frequency with the inductor and then use a toothpick to push the

other end of inductor to ground, effectively shorting it and make the

second measurement. Keep thing short, simple and ugly for best

accuracy.

- farhan

On 11/13/12, Gary, WB9JPS <gwj@spamcop.net> wrote:

> I use my N2PK VNA for really small L and C values. Since they are probably

> SMT anyway, I have a little fixture with SMA connectors on it and short

> microstrips to which I solder the parts. Then the parasitics are very low,

> and also realistic for practical installations as well. Resoluti7929 2012-11-14 07:08:03 William Carver Re: an accurate L meter For an example of using an LC oscillator to measure RF-valued coils and

capacitors see page Winter 1993 issue of Communications Quarterly.

Assuming you have a counter, cost is perhaps $20. Accuracy of 1% for

sub-1 uH coils is readily obtained.

W7AAZ

On Wed, 2012-11-14 at 20:27 +0530, Ashhar Farhan wrote:

>

> The simple way is to make an ugly vfo, measure the frequency shift

> with and without the inductor under test and calculate the inductance

> as a function of frequency shift.

> The frequency shift of relatively small inductor (compared to the

> effective inductance of the oscillator) will be a linear function of

> the additional inductance. This is beacuse the differential of square

> root is linear..

> I have measured inductances as low as 5nH with this. The precision is

> limited by precision and accuracy of the frequency counter and short

> term stability of the vfo.

> Add the unknown inductance between the coil and the ground. Measure

> the frequency with the inductor and then use a toothpick to push the

> other end of inductor to ground, effectively shorting it and make the

> second measurement. Keep thing short, simple and ugly for best

> accuracy.

> - farhan

>

> On 11/13/12, Gary, WB9JPS <gwj@spamcop.net> wrote:

> > I use my N2PK VNA for really small L and C values. Since they are

> probably

> > SMT anyway, I have a little fixture with SMA connectors7930 2012-11-14 14:49:26 kb1gmx Re: an accurate L meter