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楼主 |
发表于 2010-8-5 17:25:09
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那些都看过。但有不明白的地方请教，AN214中
The zero magnetic field ADC count would ideally be 512 for both AN0 and AN1 inputs, but in reality the counts will have some offset from one or more error sources. These sources must be subtracted from the nominal 512-count reference level. If we call the AN0 counts “X” and the AN1 counts “Y”, then circuit offset correction values Xco and Yco are measured in the factory and stored in the microcontroller’s memory. Equations like:
Xco = X – 512, Yco = Y – 512
The next data massaging is to include ferrous content correction factors from the last user calibration routine. Nearby ferrous materials may create distortions in the earth’s magnetic field at the sensor bridges, and will require both offset values and scale factor values for both X and Y counts. These values can be denoted as Xoff, Yoff, Xsf, and Ysf. Before the scale factors can be applied, the Vref count level (e.g. 512) also must be removed to arrive at numbers that are bi-directional from the normalized “0” point. Thus the equations for true heading X and Y values are:
Xh = [(X – 512 - Xco) * (Xsf)] – Xoff
Yh = [(Y – 512 – Yco) * (Ysf)] –Yoff
Once these true heading count values are determined, the compass heading (azimuth) is computed by applying the formula:
Heading = arctan (Yh/Xh)
这里的Xh = [(X – 512 - Xco) * (Xsf)] – Xoff
Yh = [(Y – 512 – Yco) * (Ysf)] –Yoff不明白是什么意思？
为什么(Y – 512 – Yco)前面说Yco = Y – 512，那Yh不是就等于1024*Xsv-Xoff了吗？
cheaven能加我QQ六-八-九-八-一-六-一帮我解答一些这个传感器的疑问吗？ |
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发表于 2010-8-3 13:24:51
