The previous pages describe the CINOX factory, our capabilities and the applications for our crystals. Of equal importance is your ability to specify the crystals which will satisfy your requirements at the lowest cost.

The first item to consider is the crystal holder. If a typical aging rate of ± 3 ppm in the first year and better than that in the following years will meet your requirements, then a resistance weld holder will be best for your application. If you require aging which is less than ± 1 ppm per year, then a coldweld holder is recommended. For some applications where shock, vibration or microphonics are a driving factor, it could be better to use one of the round TO-type holders because of the three to four point mounts available in these holders. The ultimate in miniaturization is presently only available in resistance weld packages. In general, the resistance weld package is the most economical if it can meet your electrical and mechanical requirements.

The next item to consider is whether the crystal will be operated on the fundamental mode or on one of the harmonic modes. A crystal can easily be manufactured to operate on the fundamental mode up to around 30 MHz. At that frequency the crystal is very thin and it may become desirable to operated on its 3rd harmonic. Similar decisions have to be made about operating on the 5th, 7th and 9th overtones or harmonics as frequency increases. There are "trade-offs" which will be encountered. In general, when the time comes to utilize a higher harmonic mode, the crystal becomes more rugged and less costly, but the resistance will be higher and the pullability and motional capacitance will be significantly lower. These things should be discussed with your CINOX engineering contact.

The next thing you should consider is the operating temperature range. Look at the frequency vs. temperature graphs located two topics later. If you find curves covering a two minute range which will meet your tolerances over the required temperature range, you can use an uncompensated crystal. If you have a requirement which clearly cannot be met by a crystal following these graphs, ± 1 ppm from the -30 degrees to +85 degrees C, for example, then you will have to use either a TCXO or ovenized approach.

Other parameters, such as series resistance, motional capacitance, shunt capacitance, etc. should be determined using the information in the previous topic, "Quartz Crystal Theory." Please keep in mind that compromises are often necessary when specifying a crystal because many parameters are dependent upon each other. CINOX engineering will provide you with assistance in writing the specification which will give you the best performance for the price.

While excellent OCXO crystals can be made with AT-cut crystals, the ultimate aging and phase noise are achived with SC-cut crystals.