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: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 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 > > > _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
