Just like the placement of a quartz crystal oscillator for generating clock signals, you should avoid placing the piezoelectric element itself directly above a ground plane as this creates a center-fed patch antenna. This allows the two quantities to be easily separated during measurement. The response from this sensor will have good linearity to changes in load, while it will be flat to changes in applied frequency for a constant load. You should use a high pass filter with cutoff near the first antiresonance (which has a lower frequency) and a low pass filter with cutoff near the first resonance to control the response range. If you are measuring across a range of frequencies, the usable range will lie between the first antiresonance and the first resonance. You can then use a bandpass filter in your board to remove responses at other frequencies. If you want to use a piezoelectric transducer to measure vibrations at a specific frequency, you should try to select a piezoelectric transducer with a resonance that matches the particular frequency you wish to measure. Crystals have much better long-term stability and are a better choice for high temperature measurements. Ceramic piezoelectric elements have lower costs and have sensitivities that can reach two orders of magnitude higher than piezoelectric crystals (i.e., quartz), but their sensitivity degrades over time, especially at higher temperature. The first point to make here is in choosing the right type of piezoelectric element for use in your device. Placing Piezoelectric Elements on Your PCB Utilizing sensors and transducers properly in your designs can be beneficial for device accuracy For this reason, you should be mindful of the frequency response if you want your transducer to respond in the linear regime. Changing the frequency of an input AC signal at a constant voltage will eventually cause the acoustic vibration of the transducer to change nonlinearly as you near a resonance or antiresonance. When working with a piezoelectric transducer, you will need to take this frequency response into account. This change in resonance is used to gather very sensitive biological and chemical measurements as the change in the vibration amplitude will be extremely sensitive near resonance. When a mechanical load is applied to the element, the frequencies in the response spectrum will shift to different values, and the magnitude of this shift is proportional to the applied load. If you want to use a piezoelectric element as a transducer in your board, it can be excited at multiple resonance frequencies. One important point here is that any vibrating mechanical membrane, which includes a piezoelectric crystal, has a spectrum of natural frequencies, not just a single resonance.įurthermore, the equivalent electronic circuit formed by a piezoelectric element has multiple resonance and antiresonance frequencies. ![]() In the case of an oscillating mechanical vibration, the output voltage also oscillates at the same frequency as the mechanical vibration. You can then use the equivalent digital number to perform some calculations and determine some physical quantity. ![]() This voltage can then be converted to digital data with an analog-digital converter (ADC) on your board. In the simplest sense, a piezoelectric material used as a sensor converts an applied mechanical load to an electric field, which can then be measured as a voltage. They are also manufactured in a variety of sizes, making them suitable for mounting on a PCB or as a packaged unit that attaches to a board with copper wire. These sensors are rugged and can withstand very high temperatures while remaining very sensitive to changes in environmental variables. With the exception of optical measurements, many dynamic measurements are gathered by examining the output from a piezoelectric sensor. As technology progresses, more sophisticated sensors are being developed for a variety of measurements, but piezoelectric sensors and transducers are here to stay. ![]() All sensors for use in electronic systems have a common characteristic: they take some type of physical disturbance and convert it into an electrical signal. From battery-powered wrist watches to electric cigarette lighters, piezoelectric elements play an important role in many devices, especially as a clock in digital circuits.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |