Problem: The factory inspection crystals found in the customer acceptance frequency of 20 to 30 percent failed.
Analysis: This phenomenon is systematic error of customers and suppliers of measurement equipment caused. When the current precision quartz crystal resonator of the instrument with no load capacitance measuring quartz resonator frequency can reach 2 × 10-6, but in the crystal load capacitance measurement with relatively difficult to ensure its accuracy. Commitment to ensure the accuracy of the instrument manufacturer for 1PF capacitance frequency pulling amount. This is due to the small capacitance measuring instrument was not accurate enough cause, in fact instruments of the load capacitance measurement accuracy can reach 0.2 ~ 0.5pF, therefore 5-10ppm error is easily occur. In particular, the fundamental frequency of the load capacitance is small crystal elements, each towing capacity pF capacitor can produce about 50 × 10-6. And measuring instruments of different manufacturers and the same instrument using different measurement methods, the results generated have different.
The solution is more stringent requirements for the frequency deviation of the resonator (eg less than 10ppm), placing orders while providing samples or samples provided by the manufacturer by the customer, both measuring system than the error in determining the direction and value, by suppliers corrected at the factory measurements.
