High and low frequency measurement voltage output type piezoelectric accelerometer sensor

High frequency cutoff frequency of the sensor

The high frequency cutoff frequency refers to the highest frequency signal that can be measured within the specified sensor frequency response amplitude error (±5%, ±10% or ±3dB). The high frequency cutoff frequency is directly related to the error value. The larger the specified error range, the higher the corresponding high frequency cutoff frequency. Therefore, the high frequency cutoff frequency indicators of different sensors must be compared under the same error conditions.

The sensitive core of a sensor with a high high-frequency cutoff frequency must have a high natural frequency, so the sensitivity of the sensor is relatively low. When selecting a sensor for high-frequency measurement, in order to meet the high-frequency frequency response index of the sensor, it is necessary to appropriately reduce the sensitivity requirements. The high-frequency characteristics of a piezoelectric accelerometer depend on the first-order resonant frequency of the sensor's mechanical structure. In actual use, the first-order resonant frequency of the sensor is often its installation resonant frequency. The installation resonant frequency is determined by the natural frequency of the sensitive core inside the sensor, the overall mass of the sensor, and the installation coupling stiffness. The level of the installation resonant frequency will directly affect the high-frequency measurement range of the sensor, so under the premise of having a stable sensitive core resonant frequency, improving the installation coupling stiffness is an important condition to ensure high-frequency measurement.

Under the same installation conditions, the lighter the sensor, the higher its installation resonance frequency and high-frequency cutoff frequency. Of course, the most basic factor that determines the high-frequency response of the sensor is the natural frequency of the sensitive core inside the sensor. The internal sensitive core of BW-sensor adopts advanced memory metal from abroad. The sensitive core not only has a high natural frequency but also has very stable frequency response characteristics. The high-frequency response characteristics and consistency of BW-sensor are far superior to shear-type accelerometers designed and manufactured only by component tolerance matching or mounting screw tightening.

Sensor installation form, installation resonant frequency

The high-frequency cutoff frequencies provided by sensor manufacturers are obtained under ideal installation conditions. In actual use, the different installation forms and installation quality of the sensor will directly affect the installation coupling stiffness, and then change the high-frequency cutoff frequency of the sensor. The characteristics of different installation resonant frequencies corresponding to different installation methods (screws, bonding, magnetic base and handheld) have been described in many vibration measurement literature; but it is necessary to point out that when different forms of installation methods are combined (such as screw installation with magnetic base), the high-frequency response of the sensor will be restricted by the installation form with the lowest frequency response. The installation method of high-frequency measurement often adopts screw installation. In order to achieve the ideal effect, the surface of the measured object must meet the specified flatness and finish requirements and the specified torque when the sensor is installed, so as to increase the installation coupling stiffness as much as possible to ensure the high-frequency cutoff frequency of the sensor. The higher the high-frequency cutoff frequency of the sensor, the higher the installation requirements of the sensor. Therefore, users who use high-frequency measurement sensors must take the installation of the sensor seriously.

The influence of the sensor output connector and cable on the measurement signal

传感器的信号输出接头也是潜在的影响高频测量的重要因素。在实际应用中传感器的接头和电缆也是传感器的组成部分。各种形式的接头，电缆接头与传感器的联接，以及电缆的重量和电缆相对于被测物体的固定形式也将直接影响传感器的谐振频率。传感器的重量越轻，接头和电缆对高频测量的影响越显著。所以当安装条件许可的情况下小型高频测量传感器的接头形式应首先考虑联体电缆，联体电缆具有可动零件少，重量轻的特点，比较适合高频测量。

Typical high frequency measurement sensors

Low impedance voltage output type

D111/D112 sensitivity 1mV/ms-2, frequency range 0.5Hz~10kHz, M5 top/side output

Weight: 12g, Size: 13mm (hexagonal) x 19mm (height), M5 screw mounting

D121/D122 sensitivity 2mV/ms-2, frequency range 0.5Hz~10kHz, M5 top/side output

Weight: 12g, Size: 13mm (hexagonal) x 19mm (height), M5 screw mounting

Charge output type

D21100 sensitivity 0.1pC/ms-2, frequency range 1Hz~12kHz, M5 top output

Weight: 7 grams, size: 10mm (hexagonal) x 19mm (height), one-piece M6 screw installation

D21103 sensitivity 0.1pC/ms-2, frequency range 1Hz~12kHz, M5 top output

Weight: 7 grams, size: 10mm (hexagonal) x 23mm (height), shell insulation, M6 screw installation

D221/D222 sensitivity 0.3pC/ms-2, frequency range 1Hz~12kHz, M5 top/one-piece cable side output

Weight: 2 grams, size: 7mm (hexagonal) x 12~16mm (height), M3 screw installation

Low Frequency:

Charge output type Accelerometer Not suitable for low frequency measurement

Since the acceleration signals of low-frequency vibrations are very small, and the high-impedance small charge signals are very susceptible to interference; the larger the volume of the measured object and the lower the measurement frequency, the more prominent the signal-to-noise ratio problem is. Therefore, as acceleration sensors with built-in circuits are becoming more and more common, low-impedance voltage output piezoelectric acceleration sensors with relatively small electrical noise and excellent low-frequency characteristics should be used as much as possible.