Why piezoelectric sensors can t measure static signals

Reason: Piezoelectric sensors are acceleration sensors, and there is no acceleration in static, so they cannot measure static signals, nor can they measure uniform motion.

Piezoelectric sensors are sensors based on the piezoelectric effect. It is a self-generating and electromechanical conversion sensor. Its sensitive elements are made of piezoelectric materials.

When a piezoelectric material is stressed, an electric charge is generated on the surface. This charge is amplified and converted by the charge amplifier and the measuring circuit to become the output of electricity proportional to the external force. Piezoelectric sensors are used to measure non-electrophysical quantities in which forces and energy can be converted into electricity.

The piezoelectric effect can be divided into positive piezoelectric effect and inverse piezoelectric effect.

Positive piezoelectric effect refers to:

When the crystal is subjected to an external force in a fixed direction, the internal polarization phenomenon occurs, and at the same time, a charge with opposite signs is generated on two surfaces. When the external force is withdrawn, the crystal returns to an uncharged state; When the direction of the external force changes, the polarity of the charge also changes; The amount of charge generated by the force applied to the crystal is directly proportional to the magnitude of the external force. Piezoelectric sensors are mostly made using the positive piezoelectric effect.

What is the inverse piezoelectric effect:

The phenomenon of mechanical deformation of crystals caused by the application of an alternating electric field to crystals is also known as electrostrictive effect. Transmitters made with the inverse piezoelectric effect can be used in electroacoustic and ultrasonic engineering. The force deformation of piezoelectric sensitive components includes thickness deformation type, length deformation type, volume deformation type, thickness shear type, and plane shear type.

5 basic forms.

Piezoelectric crystals are anisotropic, and not all crystals can be here.

Piezoelectric effect is generated in 5 states. For example, quartz crystals do not have volumetric deformation piezoelectric effects, but have good thickness deformation and length deformation piezoelectric effects.

Extended Materials. The main parameters of piezoelectric sensors:

1) Piezoelectric constant is a parameter to measure the strength of the piezoelectric effect of a material, which is directly related to the sensitivity of the piezoelectric output.

2) The elastic constant of piezoelectric materials

The stiffness determines the natural frequencies and dynamic characteristics of piezoelectric devices.

3) For a certain shape,

size piezoelectric elements whose intrinsic capacitance is related to the dielectric constant;

The intrinsic capacitance in turn influences the lower frequency limit of the piezoelectric sensor.

4) In the piezoelectric effect, the mechanical coupling coefficient is equal to the square root of the ratio of the converted output energy (e.g., electrical energy) to the input energy (e.g., mechanical energy);

It is an important parameter to measure the electromechanical energy conversion efficiency of piezoelectric materials.

5) The insulation resistance of the piezoelectric material will reduce the charge leakage, thereby improving the low-frequency characteristics of the piezoelectric sensor.

6) The temperature at which the piezoelectric material begins to lose its piezoelectric properties is called the Curie point temperature.

Encyclopedia - Piezoelectric sensors.

Piezoelectric sensors only have a voltage output when the pressure changes, and when there is a constant stationary pressure pressed on it, there will be no output voltage. That is, the piezoelectric sensor uses the corresponding electrical signal generated by the movement of the measured object, while the static one cannot generate the corresponding electrical signal. (Second answer:.)

When the force acting on the piezoelectric element is a static force, the input voltage of the preamplifier is equal to zero, and the fundamental reason is that the charge generated by the static force will immediately pass through the input resistance of the preamplifier and the leakage of the sensor itself, so the piezoelectric sensor is only suitable for dynamic measurement and cannot be used for static measurement. ）

Because piezoelectric sensors only have a signal output when they are dynamic, they cannot be used for static measurements because they do not have a signal output regardless of whether they are under pressure or not, regardless of how high the pressure is.

Piezoelectric sensors belong to acceleration.

If the sensor is static, there is no acceleration, so it cannot measure static signals, nor can it measure uniform motion. There is only a signal output when the dynamic speed is in motion, and there is no signal output in the static situation, regardless of whether it is under pressure or not, and how much pressure there is.

Piezoelectric sensors utilize certain dielectrics.

The piezoelectric effect produced by force.

made of sensors. The piezoelectric effect can be divided into positive piezoelectric effect and inverse piezoelectric effect.

The positive piezoelectric effect refers to the fact that when the crystal is subjected to an external force in a fixed direction, the internal polarization phenomenon is generated, and at the same time, opposite signs of charges are generated on two surfaces; When the external force is withdrawn, the crystal returns to an uncharged state; When the direction of the external force changes, the polarity of the charge also changes; The amount of charge produced by the force applied to the crystal.

It is directly proportional to the magnitude of the external force.

Piezoelectric sensors are mostly made using the positive piezoelectric effect. The inverse piezoelectric effect refers to the phenomenon of mechanical deformation of the crystal caused by the application of an alternating electric field to the crystal, also known as the electrostrictive effect. Transmitters manufactured with the inverse piezoelectric effect.

It can be used for electroacoustic and ultrasonic engineering.

Types of piezoelectric sensors:

Piezoelectric sensors can be roughly divided into 4 types, namely: piezoelectric load cells, piezoelectric pressure sensors.

Piezoelectric accelerometers and polymer pressure sensors.

The above content reference: Encyclopedia - piezoelectric sensors.

Reason: Because piezoelectric sensors only have a signal output when they are dynamic, they cannot be used for static measurements because they have no signal output regardless of whether they are under pressure or not, and how much pressure they are in static.

The measurement method of measuring the measured during dynamic measurement is constantly changing with time during the measurement process. Generally, it is necessary to observe at a certain starting point for a few minutes in order to carry out the initialization work. After that, the moving receiver automatically makes observations at predetermined sampling intervals, and determines the spatial position of the sampling point in real time together with the synchronous observation data from the reference station.

At present, the accuracy of its positioning can reach the centimeter level.

In addition, according to whether the measurement sensitive element is in contact with the measured medium, it can be divided into contact measurement and non-contact measurement; According to whether the measurement system applies energy to the measured object, it can be divided into active measurement and passive measurement.

Since the charge after the action of an external force is only saved if the loop has an infinite input impedance, which is not the case, this determines that piezoelectric sensors can only measure dynamic stresses. Piezoelectric sensors are mainly used in the measurement of acceleration, pressure, and force. Piezoelectric accelerometers are a commonly used type of accelerometer.

It has the excellent characteristics of simple structure, small size, light weight and long service life.

Piezoelectric sensors can also be used to measure combustion pressure inside engines and vacuum levels. It can also be used in the military industry, for example, to measure the change in chamber pressure and the shock wave pressure at the moment when a gun bullet is fired in the chamber. It can be used to measure both large and small pressures.

Because the piezoelectric sensing element is a force-sensitive element, the piezoelectric sensor uses the corresponding electrical signal generated by the movement of the measured object, while the static one cannot generate the corresponding electrical signal.

The principle of operation of piezoelectric sensors dictates that they are only suitable for dynamic measurements, and the force acting on the piezoelectric sensor generates an electric charge. The amount of charge.

It's very faint and will leak out by itself. If the dynamic forces act, the charge can be replenished continuously without leaking completely.

Piezoelectric crystals change all the time with the change of pressure, and the static signal is of course difficult to measure.

This is due to the characteristics of piezoelectric ceramics, which can only be generated under the action of dynamic signals.

Because piezoelectric sensors use the corresponding electrical signals generated by the movement of the measured objects, while static ones cannot generate corresponding electrical signals.

Just like a generator, it can only produce electricity if an external force pushes it. Piezoelectric sensors also require an external force to generate an electric current, and we also measure the current it generates. I don't understand 5555!

What I said upstairs is complete nonsense, the piezoelectric sensor measures the force, it is the deformation caused by the pressure that causes the polarization of the non-central lattice, but it really can't be measured statically, because as long as the charge generated by the piezoelectric sensor is in the circuit it will be consumed in a kind of LC loop. In other words, a value is accurate only when it is forced. This error can only be made small enough by increasing the load to have time to read, but not static measurements.