传感器原理传感器原理 (10).ppt

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1、Principle of Sensors传感器原理电阻应变式传感器Resistance Strain-Gage Sensors 3.2.2、电阻应变计的动态特性Dynamic characteristics of Resistance Strain Gauges动态特性动态特性动态特性动态特性 Dynamic characteristics Dynamic characteristics 定义：定义：定义：定义：当测量频率较高的动态应变时应变计的响应特性。Definition:Definition:Response characteristics of strain gauge when me

2、asuring dynamic strain with high frequency.产生动态响应滞后的原因：产生动态响应滞后的原因：产生动态响应滞后的原因：产生动态响应滞后的原因：Causes of dynamic response lag:Causes of dynamic response lag:应变波从试件通过胶层、基片传到敏感栅需要一定的时间；The strain wave from the specimen through the glue layer and substrate to the sensitive gridneeds a certain time;应变波沿应变计长

3、度方向经过敏感栅需要较长的时间。It takes a long time for the strain wave to pass through the sensitive grid along the length direction of the strain gauge.对正弦应变波的响应对正弦应变波的响应对正弦应变波的响应对正弦应变波的响应Response to sinusoidal strain waves Response to sinusoidal strain waves 设一频率为 f 的正弦应变波在构件中以速度 v 沿应变片栅长方向传播，在某一瞬时 t，应变量沿构件分布如图

4、所示。设应变波波长为，则有=v/f。应变片栅长为l，瞬时t时应变计中点的瞬时应变为：Let a sinusoidal strain wave of frequency f propagate along the length of strain gauge at velocity v in the member.At a certain instantaneous t,the distribution of strain along the member is shown in the figure.Let the strain wave wavelength be,then =v/f.The

5、 instantaneous strain at the midpoint of the strain gauge when the grid length of the strain gauge is l and the instantaneous T is:对正弦应变波的响应对正弦应变波的响应对正弦应变波的响应对正弦应变波的响应Response to sinusoidal strain waves Response to sinusoidal strain waves xt为t瞬时应变片中点的坐标。应变片测得的应变为栅长 l 范围内的平均应变m，其数值等于 l 范围内应变波曲线下的面积除以

6、 l，即xt is the coordinate of the point at t instantaneous strain gauge.The strain measured by the strain gauge is the average strain m in the range of grid length l,and its value is equal to the area under the strain wave curve in the range l divided by l,that is,平均应变m与中点应变t相对误差为The relative error be

7、tween average strain m and midpoint strain t is 简化后简化后简化后简化后Simplified Simplified 由上式可见，相对误差相对误差相对误差相对误差 的大小只决定于的大小只决定于的大小只决定于的大小只决定于 的比值。的比值。的比值。的比值。It can be seen from the above formula that the relative error depends only on the ratio of .the relative error depends only on the ratio of .结论：结论：结论：

8、结论：越小，误差越小，一般可取1/10-1/20；Conclusion:Conclusion:The smaller ,the smaller the error,which is generally 1/10-1/20;When is given,the reasonable L and working frequency limit F can be determined according to the above formula.当给定时，可根据上式确定合理的l和工作频限f。The error increases with the increase of L and F;误差随l和f的

9、增大而增大；对阶跃应变波的响应对阶跃应变波的响应对阶跃应变波的响应对阶跃应变波的响应Response to step strain waves Response to step strain waves 式中 应变波在试件中的传播速度；where the propagation speed of strain wave in the specimen L L应变片长度。Strain gauge length当阶跃波沿敏感栅轴向传播时，其阶跃响应上升时间为：When the step wave propagates along the axis of the sensitive grid,the rise time of its step response is as follows:取最高工作频率 Take the highest operating 则 Then