When X occurs, the fact that the resonance large=X Ç allows the construction of a formula that allows the resonance frequency (ƒ calculated from a circuit that only takes the value of L and the most commonly used formula for C. electrons) of the LCR circuit is:

Please note that this formula does not contain any information regarding resistance (R). Although any circuit containing L must contain at least some resistors, the presence of a small number of resistors in the circuit does not greatly affect the frequency of circuit resonance. Resonant circuits designed specifically for high frequencies are affected by stray magnetic fields, inductance, and capacitance in the surrounding environment. Therefore, most high-frequency LC series resonant circuits need to be shielded to isolate them as much as possible from external influences, and can adjust the frequency range within a very small range so that they can be accurately adjusted after assembly in the circuit.

However, although this formula has been widely used in radio frequency, it is often inaccurate at low frequencies (using large inductors with significant internal resistance). In this case, a more complex formula is needed, which also takes into account resistance. The following formula can be used for low-frequency (larger internal resistance) calculations.

In many applications, careful adjustment after circuit assembly is often the determining factor for not using pure LC circuits. In many applications, they have been replaced by solid-state ceramic filters and resonant crystal tuning circuits that do not require adjustment. However, sometimes solid-state filters may generate multiple resonant frequencies at the harmonic (s) of the desired frequency. Then a single adjustable LC tuning circuit can also be included to overcome this problem.

Calculation of series circuit.

In series LCR circuits, especially during resonance, many things occur, so calculations are usually multi-stage. Many commonly used calculation formulas have been described in earlier modules of this series, but the difference now is that the task of finding relevant information about circuit conditions relies on selecting appropriate formulas and using them in the appropriate order.

For example, in the following question, it is necessary to display the value items in red, but please note that V Ç and V large values cannot be calculated first. As the value for ƒ [R (and the alternative), the reactance needs to be calculated. But sometimes, by remembering the records about series resonance (also known as variable frequency resonance) in the gray panel above, this work can be made easier without calculating V L, because X C and X L are equal at resonance, so equal voltage will be generated at both ends.