Note : With At-cut 3rd overtone and 5th overtone, lower frequency are available.

Theoretical Frequency-temperature Curves of Various Cuts

Temperature curves for AT-CUT and Tuning fork (32.768kHz)

The ratio of the shunt capacitance to the motional capacitance

It is barometer of the change in oscillation frequency caused by the change in load capacitance.

There are two frequencies when the crystal’s impedance is pure resistance. The low frequency is series resonance frequency fs and the high frequency is parallel resonance frequency fp.

To provide condition, crystal and load capacitance are connected in series or parallel, the fL is one frequency of the two frequencies when the connected impedance is only resistance. In series capacitance the low frequency is load resonance frequency. In parallel capacitance, the high frequency is load resonance frequency.

**Fundamental mode**

The main mode of the crystal. It is called the first (1st) overtone usually.**Overtone mode**

Odd numbers assigned for frequencies in terms of specified oscillation mode Standard 3rd overtone mode , followed by 5th , 7th , 9th etc.It is not actual to produce 9th overtone.

**Frequency**Expressed in Hertz, (Hz) the frequency is the oscillation output in number of cycles per second.

**Equivalent Series Resistance(ESR)**Equivalent resistance for series resonance frequency.

**Shunt capacitance(C0)**Shunt (parallel) capacitance(C0) is the capacitance between the crystal terminals. It is difference in package, usually it is less than 7.0pF

**Motional capacitance(C1)**The capacitance is the motional capacitance (series) in the equivalent electric circuit

**Motional inductance (L1)**The resistance is motional resistance (series) in the equivalent electric circuit.

**Equivalent Series Resistance(R1)**The resistance is motional resistance (series) in the equivalent electric circuit.

**Pullability**It is means that when a crystal is operating at parallel resonance, and the frequency change as a function of load capacitance CL in a parallel resonant crystal. Pullability is a function of shunt capacitance C0, motional capacitance C1 , and size of crystal.

**Load capacitance(CL)**The effective external capacitance associated with the quartz crystal which determines the load resonance frequency(fL).

**Frequency tolerance**Allowed maximum frequency deviation at room temperature(25℃) measured(relative to nominal frequency).

**Frequency stability**The maximum allowed frequency deviation compared to the measured frequency at 25℃ over operating temperature range.

**Quality Factor (Q)**The “Q” of a crystal unit is the Quality Factor or the motional arm resonance. The maximum stability that can be attained by the crystal is directly related to Q. The higher the Q , the smaller the band width (Δf ) and the steeper the reactance slope (fs-fp). External circuit reactance value changes have less effect on a high Q crystal (less pullability) than lower Q devices.

- In a resonant circuit composed of an L, C, and R, a quantity that represents the sharpness of a resonant curve, a curve that shows the relationship between the circuit current and power frequency.
**Spurious**Frequency responses other than the main or desired response, which the crystal elements have , specified in dB max. Frequency range must be specified.

**Insulation Resistance**Resistance between crystal’s leads, or between lead and case. It’s standard values is 500M Ω min //DC100V.

**Aging**Aging is very important to crystal unit. If we do not do that, the highest aging rate occurs within the first week, not one year later. The operating frequency will be over range early.