[time-nuts] Looking for QST Jan 1990 Article on Crystal S, Q & R testing By DeMaw

Brooke Clarke brooke at pacific.net
Fri Dec 22 19:52:23 UTC 2006


Hi Mike:

Thanks for the links.   I got a copy of the DeMaw article.

But what I'm looking for is a Crystal Activity Meter rather than to 
characterize crystals for filter use.  Typically these place the crystal 
in a circuit where it oscillates and an analog meter indicates activity 
(just what the meter is really indicating is not clear to me).  Since 
CAMs are no longer being made I'm trying to come up with a PIC based 
tester that would do a similar thing.  The easiest way is to probably 
use analog switches to insert a controllable resistance in series with 
the crystal, starting high and working down, to see at what the external 
series resistance the crystal will oscillate.  This value would be a 
good indicator of activity.   This is just a thought, and I'm happy to 
hear ideas on other ways to do it.

I used to work for HP in Santa Rosa supporting the instruments made in 
Kobe, Japan which included their crystal test stuff.  There are 
instruments that just do crystal characterization (E4900 series) with 
digital readouts and there are instruments (E5100 series) that have 
graphical outputs and these were used by most of the crystal 
manufacturers for characterization.  In both cases the crystal was 
connected in series between the generator and a network analyzer using a 
resistive minimal loss pad.  The method is called Z-transform.  The 
technique is for the operator to adjust the start and stop frequencies 
so that you capture the series and parallel resonant data and the 
instrument does curve fitting to come out with the crystal equivalent 
circuit values.

Methods that use conventional network analyzers are not as accurate 
since their error increases as the impedance gets farther from 50 Ohms.

Have Fun,

Brooke Clarke

w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com



Mike Suhar wrote:

>Hear are some articles on the subject worth reading:
>
>Crystal Motional Parameters, A comparison of Measurement Approaches by Jack
>R. Smith, K8ZOA, June 11, 2006
>http://www.cliftonlaboratories.com/Documents/Crystal%20Motional%20Parameters
>.pdf
>
>Lesson Plan where they measured a crystal
>http://www.omicron-lab.com/customer_examples/pdf/Measuring_Equivalent_circui
>t_of_Quartz_crystal_II.pdf
>
>Simplified Tools and Methods for Measuring Crystals by Jim Kortge, K8IQY
>http://www.k8iqy.com/testequipment/pvxo/Atlanticon2002V1R5.pdf
>
>
>
>I have done measurements using the techniques documented above.  I have used
>various pieces of equipment such as a spectrum analyzer with tracking
>generator, TAPR VNA, and the HP 3586C Selective Voltmeter with its internal
>tracking generator.  I noticed the transformer jig as documented by K8IQY
>left something to be desired in my measurements.  This was confirmed in the
>first document by K8ZOA where his table of test jigs and methods did not
>fair very well with the transformer jig.  I ended up settling on a 50 to
>12.5 ohm minimum loss pad on both sides of the crystal and the HP3586C for
>the measuring instrument. 
>
>I have not read, at least recently to remember anything about it, the QST
>1990 article. I probably have it on my QST CD collection. I will have to
>look it up.
>
>Mike
>
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Brooke Clarke
>Sent: Wednesday, December 20, 2006 5:15 PM
>To: Discussion of precise time and frequency measurement
>Subject: [time-nuts] Looking for QST Jan 1990 Article on Crystal S,Q & R
>testing By DeMaw
>
>Hi:
>
>I'm looking for  the subject article on crystal testing, or any other 
>articles on testing crystals.
>This is more related to knowing if a given crystal is alive than 
>characterizing it, i.e. a Crystal Activity Meter type thing.
>
>Have Fun,
>
>Brooke Clarke
>
>  
>




More information about the Time-nuts_lists.febo.com mailing list