The load capacitance CL is a factor for determining the "conditions" of a crystal unit when used in the oscillation circuit .In an ordinary oscillation circuit the crystal unit is used in a range where it functions as an inductive reactance in such usage ,the oscillation circuit operates as a capacitive reactance .In other words ,when the oscillation circuit is seen from both terminals of the crystal unit ,this oscillation circuit can be expressed as a series circuit of a negative resistance -R and a capacitance CL ..At that time this capacitance is called the load capacitance .The relationship between load capacitance and oscillation frequency is not linear. When the load capacitance is small, the amount of frequency variation is large ,and when the load capacitance is increased, frequency variation lowers .If the load capacitance is lessened in the oscillation circuit to secure a large allowance for the oscillation frequency ,the frequency stability will be greatly influenced even by a small change in the circuit. The load capacitance can be any values, but 10-30PF is better.
负载电容 CL 是组成振荡电路时的必备条件。在通常的振荡电路中，石英晶体谐振器作为感抗，而振荡电路作为一个容抗被使用。也就是说，当晶体两端均接入谐振回路中，振荡电路的负阻抗 -R 和电容 CL 即被测出，这时，这一电容称为负载电容。负载电容和谐振频率之间的关系不是线性的，负载电容小时，频率偏差量大，当负载电容提高时，频率偏差量减小。当振荡电路中的负载电容减少时，谐振频率发生较大的偏差，甚至当电路中发生一个小变化时，频率的稳定性就受到巨大影响。负载电容可以是任意值，但 10-30PF 会更佳。