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Frequency Tolerance / Stability Over Temperature
The Frequency Tolerance of a crystal or oscillator is defined as the initial deviation of the crystal or oscillator frequency as compared to the absolute at 25C. The Frequency Stability over temp is defined as the frequency deviation compared to the measured frequency at 25C OVER the defined operating temperature range (I.E. 0C to +70C). Stability tolerance is sometimes expressed as a percentage of frequency deviation rather than as Parts Per Million (PPM) The conversion is as follows:

.01 % = 100 PPM
.005% = 50 PPM
.001 % = 10 PPM etc.

The stability tolerance of a crystal or oscillator needs to be specified, along with the operating temperature range. For instance, a crystal may be specified as having a frequency stability tolerance of 50 PPM over an operating temperature of -45C to + 85C, and having a frequency tolerance of 50 PPM at +25C. | Site Map