Trimmer Capacitor Considerations in Practice
Trimmer capacitors are adjustable components that are used for fine-tuning RF circuits during manufacturing or maintenance. They enable adjustable tuning for frequency values and rise and fall times, allowing for recalibration if necessary. Trimmer capacitors are critical for sensitive applications such as magnetic resonance imaging (MRI), where even minor instability can have a significant impact on image output.
During MRI scans, protons in a patient's body align themselves in the same direction when exposed to a magnetic field. When a computer-generated RF signal is applied to a proton, it is disrupted and then returns to its original state of alignment. As protons realign, they emit energy that can be measured to identify different types of molecules and their locations in the body. Trimmer capacitors are used to tune the TX and RX coils to Lamor Frequency, the frequency at which this energy is emitted. Thus, proper trimmer capacitor tuning is essential for accurate MRI imaging.
To meet the demanding requirements of MRI, it is critical to select the appropriate trimmer capacitor. Voltronics, a brand of Knowles Precision Devices (KPD), has developed a unique test setup to measure Q and RF voltage breakdown at MRI operational frequencies. KPD's portfolio includes precision trimmer capacitors made of air, glass, sapphire, and PTFE dielectrics that can be used from 1 MHz to over 2 GHz and at voltages up to 20,000 VDC. These capacitors are available in precision multi-turn and half-turn formats, making them suitable for any application level.
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Q Factor |
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K Value (dielectric constant) |
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Dielectric Withstand Voltage |
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| Non-magnetic Properties |
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| Half-turn vs. Multi-turn Trimmers |
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