How do we define Crystal Frequency Tolerance & Stability over Temperature

 

 

 

 

 

 

 

 

 

The frequency tolerance of a crystal or oscillator defined as the initial deviation of a crystal or oscillator frequency when measured at 25°C. The stability over the defined operating temperature range is defined as the Frequency Deviation compared to the measured frequency at 25°C. Tolerance and stability are typically expressed as parts per million and sometimes as a percentage of the frequency.

The conversion is as follows:

  • .01% is equal to 100 PPM
  • .005% is equal to 50 PPM
  • .001% is equal to 10 PPM

As frequency tolerances are tightened costs increase incrementally. Operational Temperatures is the defined band of minimum and maxim band temperatures that the crystal could reasonably expect to encounter in its normal application.

Because there are many different applications for crystals they are offered in a variety of temperature options. The unit of measure is usually in degrees Celsius. The wider the temperature band, the more difficult and costly it is to produce the crystal. The tolerance, stability and operational temperature range needs to be specific in order to offer solutions that will perform to the customers’ expectations.

For instance, a crystal may be specified as having a frequency tolerance of ±50 PPM @ +25°C in a frequency stability of ±50PPM over an operating temperature. This would give the crystal an overall stability and tolerance budget of ±100PPm or .01% potential frequency error. Thank you for your time.