load capacitance of a quartz

U

usmgn

Guest
hi,

i would know : how measure "load capacitance" parameter on a 153.6khz quartz
(ref epson : 153.600k E 7YN)

usmgn
 
On Thu, 06 Nov 2003 18:26:04 +0100, usmgn wrote:

hi,

i would know : how measure "load capacitance" parameter on a 153.6khz quartz
(ref epson : 153.600k E 7YN)
Click to expand...
Build it into an oscillator, work out how much capacitance the circuit
presents to the crystal, the put a trimmer across the crystal, trim for
exactly the correct frequency and measure the trimmer. Add that to the
circuit capacitance and you have it.


--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
Fred Abse wrote:
On Thu, 06 Nov 2003 18:26:04 +0100, usmgn wrote:


hi,

i would know : how measure "load capacitance" parameter on a 153.6khz quartz
(ref epson : 153.600k E 7YN)


Build it into an oscillator, work out how much capacitance the circuit
presents to the crystal, the put a trimmer across the crystal, trim for
exactly the correct frequency and measure the trimmer. Add that to the
circuit capacitance and you have it.
Click to expand...
Yeah, that last sentence is the one that's unknown: circuit capacitance.

Of course, you have to have an accurate reference freq to get the
'exactly correct' frequency. Another 'minor' problem.

The manufacturer should be able to tell you something about the circuit
the xtal was made to be used in.
 
In article <boen3e$4op0q$1@hades.csu.net>, Watson A.Name "Watt Sun - the
Dark Remover" <NOSPAM@dslextreme.com> writes
Fred Abse wrote:
On Thu, 06 Nov 2003 18:26:04 +0100, usmgn wrote:


hi,

i would know : how measure "load capacitance" parameter on a 153.6khz quartz
(ref epson : 153.600k E 7YN)


Build it into an oscillator, work out how much capacitance the circuit
presents to the crystal, the put a trimmer across the crystal, trim for
exactly the correct frequency and measure the trimmer. Add that to the
circuit capacitance and you have it.

Yeah, that last sentence is the one that's unknown: circuit capacitance.

Of course, you have to have an accurate reference freq to get the
'exactly correct' frequency. Another 'minor' problem.

The manufacturer should be able to tell you something about the circuit
the xtal was made to be used in.

Two previous replies are correct.
Click to expand...
You cant measure the "parallel input capacitance " only infer it .
The manufacturer sets up a capacitance and adjusts the crystal frequency
to be correct with that value.
--
ddwyer
 
On Thu, 06 Nov 2003 15:56:35 -0800, Watson A.Name "Watt Sun - the Dark
Remover" wrote:

Of course, you have to have an accurate reference freq to get the
'exactly correct' frequency. Another 'minor' problem.
Click to expand...
I'd assumed that, if the OP was into quantifying crystals, he'd at least
have a frequency counter, or some sort of frequency substandard.
Otherwise, why bother?

Even a BC221 - remember those? :)

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
Fred Abse wrote:
Even a BC221 - remember those? :)

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
Click to expand...
Remember it? I owned one.
--


Michael A. Terrell
Central Florida
 
Fred Abse wrote:

On Thu, 06 Nov 2003 15:56:35 -0800, Watson A.Name "Watt Sun - the Dark
Remover" wrote:



Of course, you have to have an accurate reference freq to get the
'exactly correct' frequency. Another 'minor' problem.



I'd assumed that, if the OP was into quantifying crystals, he'd at least
have a frequency counter, or some sort of frequency substandard.
Otherwise, why bother?

Even a BC221 - remember those? :)



Anyone need a BC221. I have one or two that are no longer used.
Click to expand...

I like to look at them from time to time and remember what it was like
when one Hertz (cycle) at one MegaHertz was pretty good.

Bill K7NOM
 
Michael A. Terrell wrote:
Fred Abse wrote:

Even a BC221 - remember those? :)

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

Remember it? I owned one.
Click to expand...
Still got mine!


--
Graham W http://www.gcw.org.uk/ XP1800+ Page added, Graphics Tutorial
WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex
Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.
 
On Sat, 08 Nov 2003 23:30:33 +0000, Michael A. Terrell wrote:

Fred Abse wrote:

Even a BC221 - remember those? :)

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

Remember it? I owned one.
Click to expand...
So did I. A rather nice Philco-made one that someone unknown had lovingly
crafted a proper, regulated (neon stabilizer and pentode) battery
eliminator in a superb aluminum fitted cradle. I suspect some bored Army
radio tech working the night shift.

Sadly long gone. Regret it now.

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
On Sun, 09 Nov 2003 11:56:15 +0000, Graham W wrote:

Michael A. Terrell wrote:
Fred Abse wrote:

Even a BC221 - remember those? :)



Remember it? I owned one.

Still got mine!
Click to expand...
Lucky you! I wish I still had mine.

Does the temerature compensator still work on yours? I had to un-stick
mine. Lovely bit of engineering!

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx
 
Fred Abse wrote:
On Sun, 09 Nov 2003 11:56:15 +0000, Graham W wrote:

Michael A. Terrell wrote:
Fred Abse wrote:

Even a BC221 - remember those? :)



Remember it? I owned one.

Still got mine!

Lucky you! I wish I still had mine.

Does the temerature compensator still work on yours? I had to un-stick
mine. Lovely bit of engineering!
Click to expand...
I don't know, Fred. The electrons in mine stopped moving a quarter
of a century ago! 8Ź)


--
Graham W http://www.gcw.org.uk/ XP1800+ Page added, Graphics Tutorial
WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex
Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.
 
i precise my question :
i have a PIC16LF873A witch a 153.6Khz crystal.
I place a COMTEC crystal witch 12.5pf (factory spécification) load
capacitance and two 18pF capacitor to the GND. Witch this configuration i
have more than 20% of reject : oscillator dont start or oscillator stop in
cold ambiance.
I place a EPSON crystal (recovery) which a unknow capacitance load and all
work fine.
Question : why all it's ok wich EPSON crystal : it is a diferent parameter
"factory capacitance load" ? How to mesasure this factory parameter ? Is it
a bad way ?


usmgn
 
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