Quartz
Definitions
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When a crystal is operating at series resonance, it looks resistive in the circuit. In a well designed series resonant circuit correlation is not a problem and load capacitance does not have to be specified. When load capacitance is not specified Stabilix will manufacture the unit at series resonance. |
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When a crystal is operating at parallel or anti-resonance it looks inductive in the circuit. Therefore changes in circuit reactance values have the effect of pulling the frequency of the crystal. If a crystal is to be used at parallel resonance, the load capacity the crystal is looking into must be specified. This load capacity is the dynamic capacity of the total circuit, measured or computed across the crystal terminals. In parallel circuit design, the load capacity should be selected to operate the crystal at a stable point. |
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The equivalent circuit of a crystal, as illustrated on the left, is useful to explain the basic consepts governing it's behaviour. C0 represents the static capacity and is the sum of the electrode capacity and the capacities of the wire leads and holder. |
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