In principle, the CERALOCK can be classified into two series: kHz-band type and MHz-band type. The product categories are identified by the vibration mode. However, any type of CERALOCK provides oscillation frequencies (parasitic oscillation) different from the main oscillation frequency. The oscillation with parasitic frequency is called spurious oscillation. You can check the behavior of the parasitic oscillation by using an impedance analyzer such as HP4294 (manufactured by Agilent Technologies).
Generally, any type of resonator provides odd-multiple overtone frequencies. However, the CERALOCK will rarely develop spurious oscillation due to overtone frequency, except for the resonators that inherently use the 3rd-overtone frequency, such as the CSTCW/CSACW_X Series (*1).
You can check the spurious oscillation due to overtone frequency by measuring the oscillation frequency. If the oscillation frequency is nearly triple the target frequency, it is regarded as spurious oscillation due to 3rd-overtone frequency.
When the CSTCW/CSACW_X Series is used, spurious oscillation with a fundamental wave (1/3 frequency) or quintuple wave (5/3 frequency) can be observed, because 3rd-overtone oscillation frequency is equal to its target oscillation frequency.
*1) CSTCW/CSACW Series
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