Wanted: L/C Meter project

[Paul Burridge]

Hi all,

I'm finding my current meter increasingly useless as it can only
resolve relatively high values of inductance and capacitance. I really
need something that can provide accurate read outs of components in
the order of <5p and <10n. It strikes me this would make an excellent
home-build project. Does anyone have a design lying about somewhere
for such a measuring device? Perhaps something from an old QST or one
of the popular electronics magazines?
Many thanks.

p.

 

[Joel Kolstad]

I'm finding my current meter increasingly useless as it can only
resolve relatively high values of inductance and capacitance. I really
need something that can provide accurate read outs of components in
the order of <5p and <10n.

I think it's safe to say a lot of hobbyists have contstructed the Almost All
Digital Electronics LC meter here: http://www.aade.com/lcmeter.htm . It did
appear in... umm... Nuts & Volts, maybe? -- some publication -- a small
handful of years ago.

---Joel Kolstad

 

[Frank Buss]

http://www.aade.com/lcmeter.htm

If someone is interested: Same in german, but with nicer box and schematic
drawings:

http://www.spettel.de/ralf/projekte/lc-meter/index.html

 

[Spehro Pefhany]

If someone is interested: Same in german, but with nicer box and schematic
drawings:

http://www.spettel.de/ralf/projekte/lc-meter/index.html

FWIW, he wants 38 euros ($45 US) for the programmed micro.

Best regards,
Spehro Pefhany

 

[Frank Buss]

FWIW, he wants 38 euros ($45 US) for the programmed micro.

Yes, but I think the difficult part is the analog part, programming the
microcontroller is easy, so you don't need it.

But the relay for calibrating looks not very good. Is it possible to
substitute it with a chip, perhaps a 4066 quad switch? And perhaps the
other switches of the 4066 could be used to automaticly switch between L
and C mode. Then you simply test a component and the LC meter determines,
if it is a capacitor or a coil.

With some more analog switches it could be enhanced to an LCR meter and
with even more switches and microcontroller support you can integrate a
diode tester and a transistor tester, which can automaticly detect NPN or
PNP, and the pin assigment (I always forget the pin assigments, so this
would be a nice feature).

 

[Tim Shoppa]

Hi all,

I'm finding my current meter increasingly useless as it can only
resolve relatively high values of inductance and capacitance. I really
need something that can provide accurate read outs of components in
the order of <5p and <10n. It strikes me this would make an excellent
home-build project. Does anyone have a design lying about somewhere
for such a measuring device? Perhaps something from an old QST or one
of the popular electronics magazines?

In that region parasitics are often as large as the part you want to
measure.

You have three choices, IMHO:

1. Unquestioned answers. These are those digital two-terminal things
you hook a part to, you select the mode, and it gives you a number.

Those are fun to play with. Especially when the part you are measuring
gives readings in both "inductance" and "capacitance" mode

2. Unanswered questions. Some grid dip meters seem to fall into this
category. At least these get you started in thinking out of the
"this part can be characterized with a single number" zone.

3. A full-blown network analyzer.

Chances are that all three alternatives can be avoided with a little
thought and effort.

Tim.

 

[Paul Burridge]

3. A full-blown network analyzer.

Chances are that all three alternatives can be avoided with a little
thought and effort.

Thanks, Tim. I'm inclining towards option 3 at present. F*** it; it's
only money.

 

[James]

Paul wrote:

I really
need something that can provide accurate read outs of components in
the order of <5p and <10n. It strikes me this would make an excellent
home-build project. Does anyone have a design lying about somewhere
for such a measuring device? Perhaps something from an old QST or one
of the popular electronics magazines?

"Simple Digital Inductance Meter With 0.1nH Resolution," Williams, Rodger,
RF Design, Oct. 1987 pp50-55.

(a 3-linear IC design. Classy)

James

P.S. I believe the AADE design first appeared as a project in Radio Electronics
magazine, but, that aside, I don't think it has the resolving power you
request.. -j


et.net: delete it. (incoming e-mail subject to brutal filtering)