Key words: crystal inspection crystal oscillator skills target
⒈ total frequency difference: in the rules of time, due to regular operations and non-operating parameters caused by the combination of all the crystal vibration
Frequency and frequency of a given nominal frequency. It is stated that the total frequency difference includes frequency temperature stability, frequency temperature accuracy, frequency aging rate, frequency power supply
Voltage stability and frequency load stability together with the formation of the maximum frequency difference. Usually only in the short-term frequency of security care, and other frequency stability targets are not strictly requested occasions.
⒉ frequency temperature stability: in the nominal power and load, the operation within the regular temperature scale without implied
Reference temperature
Or the maximum permissible frequency offset with implied reference temperature.
FT = ± (fmax - fmin) / (fmax + fmin)
FTref = ± MAX [| (fmax-fref) / fref |, | (fmin-fref) / fref | fT: frequency temperature

Stability
(Without implied reference temperature)
FTref: frequency temperature stability (with implied reference temperature)
Fmax: the highest frequency measured in the regular temperature scale
Fmin: the lowest frequency measured in the regular temperature range
Fref: Frequency measured by the rule reference temperature
It is stated that the crystal vibrator with fTref target is more difficult to produce than the crystal vibrator with fT target, so the crystal oscillator of fTref target is higher.
⒊ frequency stability preheat time: to crystal oscillator stable output frequency as a benchmark, from the power to the output frequency is less than the regular frequency tolerance required time.
It is stated that in most of the applications, the crystal vibrator is energized for a long time, but in some applications the crystal vibrator needs
Frequent start-up and shutdown, when the frequency of preheating time to meet the target needs to be considered (especially on the use of military communications in harsh environments, when the request frequency temperature stability ≤ ± 0.3ppm (-45 ℃ ~ 85 ℃ ), The choice of OCXO as the local oscillator, the frequency of preheating time will be not less than 5 minutes, and the choice of DTCXO only need more than ten seconds)

⒋ frequency aging rate: in a stable environment to measure the vibrator frequency, the vibrator frequency and the relationship between the moment. This long-term frequency drift is formed by the slow change of the crystal element and the vibrator circuit element, and the available time limit
(Such as ± 10 ppb / day, after 72 hours of power up), or the maximum total frequency change in the regular time frame (eg,
± 1 ppm / (first year) and ± 5 ppm / (ten years)).
It is stated that the aging rate of TCXO is ± 0.2ppm ~ ± 2ppm (first year) and ± 1ppm ~
± 10ppm (except for special circumstances, TCXO rarely use the daily frequency of the aging rate of the target, even under the conditions of the laboratory, the temperature changes caused by changes in the frequency will greatly exceed the temperature of the crystal oscillator vibrator daily frequency aging , So this goal loses the meaning of practice). OCXO frequency aging rate: ± 0.5ppb ~ ± 10ppb / day (after 72 hours of power), ± 30ppb ~ ± 2ppm (first year), ± 0.3ppm ~ ± 3ppm (ten years)

⒌ frequency voltage control scale: the frequency control voltage from the reference voltage to the end of the rule voltage, crystal vibration
The minimum peak change in the frequency of the device.
It is stated that the reference voltage is + 2.5V and the end of the rule is + 0.5V and + 4.5V. The voltage-controlled crystal oscillator is controlled at + 0.5V frequency. The frequency change is -110ppm. When the voltage is controlled at + 4.5V frequency The amount of change is + 130ppm, then VCXO voltage control frequency voltage control scale shows: ≥ ± 100ppm (2.5V ± 2V).