EMRFD Message Archive 7925

Message Date From Subject
7925 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

Paul
7926 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. Resoluti
7927 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
>
>
>



--

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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. Resoluti
7929 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 connectors
7930 2012-11-14 14:49:26 kb1gmx Re: an accurate L meter