Crystal Motional Parameters

Ever tried searching through your datasheets for the motional parameters of that quartz crystal you just bought? Good luck! Vendors simply don’t specify these parameters to general end users, and for most applications that’s OK. But for high Q oscillator and filter design, measuring and matching crystals can be important.

This video discusses crystal motional parameters, how to measure them with a crystal impedance meter, and finally examines the measured values of 150+ real world crystals.

Below are some interesting correlations/statistics gathered from the measured data; raw measurement data is available here.

Average C0 capacitance for each crystal holder type

Average C0 capacitance for each crystal holder type

Average motional resistance vs frequency

Average motional resistance vs frequency

Average motional inductance vs frequency

Average motional inductance vs frequency

Average unloaded Q vs frequency

Average unloaded Q vs frequency

Average unloaded Q for each crystal holder type

Average unloaded Q for each crystal holder type

Unloaded Q of glass-sealed crystals vs average unloaded Q

Unloaded Q of glass-sealed crystals vs average unloaded Q

Overall statistical analysis of unloaded crystal Qs

Overall statistical analysis of unloaded crystal Qs

References and additional reading:

Description Reference
Crystal motional parameters and relevant equations Understanding Quartz Crystals and Oscillators, Ramon M. Cerda, Chapter 1.27
Measuring quartz crystal parameters Measurement of the equivalent circuit of a quartz crystal, Omicron Lab
Crystal measurements with a VNA Crystal Bandpass Filters, W0QE
Crystal measurements with a Spectrum Analyzer Crystal Parameters — Experiments with a Tracking Generator + Spectrum Analyzer, QRP HomeBuilder
Comparison of crystal measurement techniques Crystal Motional Parameters: A Comparison of Measurement Approaches, Jack R. Smith, K8ZOA
Crystal test fixture design Assembly and Usage Notes for K8ZOA Crystal Test Fixture Revised for Version 1.2 PCB, Jack R. Smith, K8ZOA