Comparison of passive and active aging of SC-cut and AT-cut crystals

This paper reports on the results of pre-aging of four different types of OCXO crystal units. It compares the aging behaviour for a passive aging at +80/spl deg/C over 28 days and 12 days at different drive levels and the active aging in the following 34 days with the crystals continuously operating in oscillators. For the aging rates good correlation was found. One crystal of each group was additionally aged for 240 days. The measured long-term aging results are compared to the aging prediction derived from the first 30 days.