CN0189: 使用双轴加速度计进行倾斜测量

概览

优势和特点
• 在90度和温度范围内具有1度的精度
• 双轴确保高精
• 滤波降低带内噪声
• 精密倾斜应用
• 病人监护
• 侧翻和稳定性控制
• 传感器和传感器接口
设计资源
设计和集成文件
• 原理图
• 物料清单
• Gerber Files
• Assembly Drawing
评估硬件
Part numbers with "Z" indicate RoHS Compliance.

• EVAL-CFTL-6V-PWRZ (\$ 17.00) Wall Power Supply for Eval Board
• EVAL-CN0189-SDPZ (\$ 60.00) Tilt Measurement Using a Dual Axis Accelerometer
• EVAL-SDP-CB1Z (\$ 99.00) Eval Control Board

设备驱动
Software, such as C code and/or FPGA code, used to communicate with a component's digital interface.
连接支持
This circuit supports 3rd party connectivity.

电路功能与优势

 Figure 1. Dual Axis Tilt Measurement System (Simplified Schematic: Decoupling and All Connections Not Shown)

电路描述

ADXL203输出是比率式的；当电源电压升高时，输出电压也会升高。输出灵敏度与电源电压成比例。VS = 3 V时，输出灵敏度典型值为560 mV/g。Vs = 5 V时，该器件的标称灵敏度为1000 mV/g

g输出电平也是比率式的，因此所有电源电压情况下，零g输出的标称值均等于VS/2。

BW = 1/(2πR×C(X,Y)), where R = 32 kΩ

RMS Noise = (110 μg/√Hz) × √(BW × 1.57)

 Figure 2. Output Response vs. Orientation

VMAX (+1 g) = (2.6 V) + (1040 mV/g)×(+1 g) = 3.64 V

VMIN (−1 g) = (2.4 V) + (1040 mV/g)×(−1 g) = 1.36 V

AX, OUT [g] = 1 g × sinθ

θ = sin -1 (AX, OUT [g]/ g)

 Figure 3. Single Axis Used for Tilt Sensing

 Figure 4. Output Acceleration vs. Angle of Inclination for Single Axis Inclination Sensing

 Figure 5. Two Axes Used for Tilt Sensing

 Figure 6. Output Acceleration vs. Angle of Inclination for Dual-Axis Incination Sensing

AX, OUT [g] = 1 g × sin θ
AY, OUT [g] = 1 g × cos θ

θ = sin-1 (AX, OUT [g]/ 1 g)

θ = cos-1 (AY, OUT [g]/ 1 g)

 Figure 7. Calculated Angle Error Due to Accelerometer Offset

 Figure 8. Calculated Angle Error Due to Accelerometer Sensitivity Mismatch

AOUT[g] = AOFF + ( 增益 × AACTUAL)

AOFF是失调误差，单位为g.
Gain是加速度计的增益，理想值为1。
AACTUAL是作用于加速度计的实际加速度，理想值为g.

A+1g[g] = AOFF + (1 g × 增益)
A−1g [g] = AOFF + (−1 g × 增益)

AOFF [g] = 0.5 × (A+1g[g] + A-1g[g])

AACTUAL[g] = (AOUT – AOFF) / 增益

T测试结果
PCB安装于能够自由旋转360°的板上，并用上述校准技术取得了一组数据（找出X和Y轴的+1 g和−1 g值来确定各个轴的失调和灵敏度）。通过调整PCB，使得Y轴输出+1 g电平(~3.5 V)，X轴输出0 g电平(~2.5 V)。经过校准后，将此方向视为0°。

 图9. 输入角度与输出角度之间的关系（以arcsin (X)进行计算）
 Figure 10. Input Angle vs. Output Angle Calculated as arcos(Y)
 图11. 输入角度与输出角度之间的关系（以arctan(X/Y)进行计算）

PCB布局考虑

电路评估与测试

• 带USB端口的Windows® XP、Windows Vista®（32位）或Windows® 7（32位）PC
• EVAL-CN0189-SDPZ电路评估板
• EVAL-SDP-CB1Z SDP评估板
• CN-0189评估软件
• 电源：+6 V或+6 V“壁式电源适配器”

EVAL-CN0189-SDPZ电路板上的120引脚连接器连接到 EVAL-SDP-CB1Z(SDP)评估板上标有“CON A”的连接器。应使用尼龙五金配件，通过120引脚连接器两端的孔牢牢固定这两片板。利用合适的RF电缆，通过SMA RF输入连接器将RF信号源连接到EVAL-CN0189-SDPZ板。

此电路中所用产品:

EVAL-CFTL-6V-PWRZ Wall Power Supply for Eval Board \$ 17.00 Yes
EVAL-CN0189-SDPZ Tilt Measurement Using a Dual Axis Accelerometer \$ 60.00 Yes
EVAL-SDP-CB1Z Eval Control Board \$ 99.00 Yes

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