Observing the aging rate of high stability crystal oscillators from a longer time scale shows a decreasing trend as heating time continues. Therefore, when examining the annual aging rate of high stability crystal oscillators abroad, it is often based on the daily aging rate multiplied by a coefficient.

The meaning and measurement of daily frequency fluctuations:

Daily frequency fluctuation refers to the maximum change in frequency value of an oscillator within 24 hours after a specified preheating time. Some of the daily frequency fluctuations reflect a certain section of the aging effect curve, while others reflect the influence of factory noise.

Generally speaking, during a relatively short preheating time, the maximum change in frequency value is reflected, and unidirectional aging drift is the main factor; In this case, both are at the ends of the measured value, and in various frequency standards, the frequency modulation noise contained has slow changing components (the frequency can reach one week per year). This type of noise affects the frequency stability of sampling times such as hours and days, and when measuring daily frequency fluctuations, it generally includes the maximum frequency change within a day without further distinction. So for some crystal oscillators with high noise in certain factories, or when measuring the daily frequency fluctuations of crystal oscillators with long preheating times, different values may appear. For frequency sources that mainly drift in one direction, due to the logarithmic aging law, the longer the preheating time of most crystal oscillators, the smaller the daily frequency fluctuations.

For the measurement of daily frequency fluctuations, if ordinary counting measuring instruments are used, a sampling time of more than 10 seconds is adopted to improve the measurement resolution, and the sampling period is generally one hour.

For daily frequency fluctuations, some countries no longer use it as a specialized technical indicator because daily frequency fluctuations can often be manifested as the combined effects of aging rate, frequency stability, and temperature on oscillator frequency; However, this parameter is still used in some regulations and technical specifications of products in China.

Measurement of NTP Server Startup Characteristics:

The startup characteristics of NTP time servers refer to the method of measuring the maximum and minimum frequency values of the oscillator's frequency value after initial preheating over a period of time.

The NTP time server startup feature is a high-resolution measurement that is taken continuously every hour one hour after the entire machine is turned on. If the counting measurement method is used, the sampling time is 10 seconds, and the continuous measurement is for 7 hours. According to the above method, the maximum frequency change within 4 hours after one hour of startup and the maximum frequency change within 4 hours after 4 hours of startup are calculated; In addition, there are also measurements of startup characteristics within 8 hours after 3 hours of startup and within 8 hours after 6 hours of startup.