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load capacitance of a quartz

U

usmgn

Jan 1, 1970
0
hi,

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

usmgn
 
F

Fred Abse

Jan 1, 1970
0
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.
 
W

Watson A.Name \Watt Sun - the Dark Remover\

Jan 1, 1970
0
Fred said:
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.
 
D

ddwyer

Jan 1, 1970
0
Watson A.Name "Watt Sun - the said:
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.
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.
 
F

Fred Abse

Jan 1, 1970
0
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? :)
 
B

Bill Janssen

Jan 1, 1970
0
Fred said:
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.

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
 
F

Fred Abse

Jan 1, 1970
0
Remember it? I owned one.

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.
 
F

Fred Abse

Jan 1, 1970
0
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!
 
G

Graham W

Jan 1, 1970
0
Fred said:
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!

I don't know, Fred. The electrons in mine stopped moving a quarter
of a century ago! 8¬)
 
U

usmgn

Jan 1, 1970
0
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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