Vibration sensor
The piezoelectric film is one of the earliest application of violin pickup. Later, Gibson Guitar Company made saddle string code string code installed in the pickup launched a series of acoustic guitar with piezoelectric film. This pickup is very high fidelity leads to a series of vibration sensor and acceleration meter application.
Musical instrument pickup
At present, the piezoelectric film is picked up in the guitar
There are four design schemes for the application of the sound device:
The first kind is thick film, compression type
Force type (under string code) design;
The two is a low cost accelerometer.
The other two are contact microphones,
One is a saddle wrapped in a string code.
In shape, the other is glued to the instrument
The pickup. Due to the low value of Q self resonant no ceramic pickup.
Please take a look at the folding scheme of figure 57. The hot side is a slightly narrow electrode on the inside. Because shielding is made of piezoelectric material, folding technology can provide higher pick up sensitivity than other shielding methods. The traditional shielding layer can be made of multilayer piezoelectric film, viscose and shielding foil easily.
Machine monitoring
The high fidelity of the shielded piezoelectric film sensor in the instrument has led to the development of the vibration sensors used in the machine monitoring. In its simplest mode, a piezoelectric film vibration sensor is basically like a dynamic strain gauge. The piezoelectric film does not require an external power supply, but the signal is larger than the signal amplified by the strain gauge. A typical piezoelectric membrane sensor generates a voltage signal of 4 orders of magnitude larger than that of foil type strain gauge, which is 2 orders higher than that of semiconductor type, and the frequency response of piezoelectric film strain gauge is also excellent.
The high sensitivity is due to the shape of the piezoelectric membrane material. The thickness of the small material means a very small cross-sectional area. Therefore, very small longitudinal force can cause very large stress in the material.
The piezoelectric film sensor can be attached to the vibration surface to monitor the frequency and amplitude of the vibration structure. This sensor covers a larger area than a common strain gauge, so for a meaningful result, a direct comparison should be made in a uniform strain field. It is clear that the point sensor always needs it, although the capacitance of the small sensor is small, and the additional factors should be considered in the design. Using the traditional charge amplifier, or because of the relatively high signal level, the high impedance field effect transistor buffer circuit can achieve a frequency of a few hertz.
Bearing wear detector
A shielded piezoelectric film sensor has been used to monitor the wear and tear of the bearings. The sensor is permanently glued to the outer surface of the bearing sleeve with epoxy resin. Because of its small quality and small shape, it can be used as a built-in nondestructive testing sensor for bearing, without wasting time to repair the accelerometers regularly.
Fan air flow sensor
A laminated beam sensor is used as a fault sensor for the centrifugal fan in the pipeline air flow. The oscillation of about 100Hz in the sensor caused by the turbulence effect is measured in the presence of air flow. When there is no air flow, the signal disappears and triggers the circuit to work. The sensor and switch point path is composed of a double field effect transistor operational amplifier with TL084 four sets, and the standard input signal is 80mV. The reliability of the sensor is the key feature, but because it does not actually be subjected to any stress, the working life is unrestricted.
Yarn breaking sensor
The textile mill needs to break the yarn for thousands of yarns
Monitor? Once a leak will lead to a large amount of material scrap,
The labor cost of producing these materials is beyond its manufacture
Cost. When the switch is falling, yarn, switch
The contact is closed, very unreliable. The fiber crumbs will be stuck
The connection of the switch so that the output signal is not produced.
. The piezoelectric film vibration sensor is loaded on thin steel sheets
On the top, we monitor the sound signal generated by friction when the yarn slid through the steel sheet, which is similar to the violin string (Fig. 58). Once the vibration is stopped, it will immediately trigger the machine to stop.
Vending machine sensor
The piezo film dynamic strain gauge with the shielding layer is attached under the shipping slot to inspect the product. The vibration generated by the non collision will send out a "fault" alarm signal. The second application is the coin machine, which is counted by a piezoelectric film device. The sensors confirm the coins won, so that gamblers are afraid to make a malfunction at random. In the ticket dispenser, the beam type piezoelectric film device is used to count the tickets.
