Trimmer Capacitor


What are trimmer capacitors? Trimmer capacitors are variable capacitors which serve the purpose of initial calibration of equipment during manufacturing or servicing. They are not intended for end-user interaction. Trimmer capacitors are almost always mounted directly on the PCB (Printed Circuit Board), so the user does not have access to them, and set during manufacturing using a small screwdriver. Due to their nature, trimmer capacitors are cheaper than full sized variable capacitors and rated for many fewer adjustments. Trimmer capacitors are used to initially set oscillator frequency values, latencies, rise and fall times and other variables in a circuit. Should the values drift over time, these trimmer capacitors allow repairmen to re-calibrate equipment when needed. There are two types of trimmer capacitors: air trimmer capacitor and ceramic trimmer capacitor. Trimmer capacitor definition A trimmer capacitor is a variable capacitor used for initial calibration and recalibration of equipment. It is commonly mounted directly on a PCB and accessed only by professional repairmen, not the end-user. Characteristics Voltage rating, capacitance range, polarity Trimmer capacitors can be rated for voltages up to 300 volts, although voltage ratings of up to 100 volts are much more common. Since trim caps are variable capacitors, they come in a capacitance range rather than a single capacitance value. The minimum capacitance is usually between 0.5 pF and 10 pF, while the maximum capacitance is usually between 1 pF and 120 pF. The actual capacitance value can be varied between the minimum and maximum capacitance values for a given trimmer capacitor, but it can never be set to zero. It is worth noting that trimmer capacitors are not polarized. Tolerances and accuracy Trimmer capacitors do not boast a good capacitance value tolerance. Sometimes, the tolerances can be as high as -0 to +100%. This means that a trimmer [… read more]