ADIS16448AMLZ Datasheet, PDF (20/24 Pages) Analog Devices – Compact, Precision Ten Degrees of Freedom Inertial Sensor

ADIS16448
Data Sheet
Accelerometer Bias Correction Factors
When the bias estimate is complete, multiply the estimate by
−1 to change its polarity, convert it to the digital format for the
offset correction registers (see Table 40, Table 41 or Table 42)
and write the correction factors to the correction registers. For
example, lower the x-axis bias by 12 LSB (10 mg) by setting
XACCL_OFF = 0xFFF4 (DIN = 0xA1FF, 0xA0F4).
Point of Percussion Alignment
Set MSC_CTRL[6] = 1 (DIN = 0xB446) to enable this feature
and maintain the factory default settings for DIO1. This feature
performs a point of percussion translation to the point identified
in Figure 22. See Table 30 for more information on MSC_CTRL.
ORIGIN ALIGNMENT
REFERENCE POINT
SEE MSC_CTRL[6].
Figure 22. Point of Percussion Physical Reference
MAGNETOMETER CALIBRATION
The ADIS16448 provides registers that contribute to both hard
iron and soft iron correction factors, as shown in Figure 23.
1 + xMAGN_SIC
MAGNETIC
SENSOR
ADC
FACTORY
CALIBRATION
AND FILTERING
xMAGN_OUT
xMAGN_HIC
Figure 23. Hard Iron and Soft Iron Factor Correction
Hard Iron Correction
The XMAGN_HIC (see Table 43), YMAGN_HIC (see
Table 44), and ZMAGN_HIC (see Table 45) registers provide
the user programmable bias adjustment function for the X-, Y-,
and Z-axis magnetometers, respectively. Hard iron effects
result in an offset of the magnetometer response.
Table 43. XMAGN_HIC (Base Address = 0x26), Read/Write
Bits
Description (Default = 0x0000)
[15:0]
X-axis hard iron correction factor,
twos complement, 7 LSB/mgauss, 0x0000 = 0
Table 44. YMAGN_HIC (Base Address = 0x28), Read/Write
Bits
Description (Default = 0x0000)
[15:0]
Y-axis hard iron correction factor,
twos complement, 7 LSB/mgauss, 0x0000 = 0
Table 45. ZMAGN_HIC (Base Address = 0x2A), Read/Write
Bits
Description (Default = 0x0000)
[15:0]
Z-axis hard iron correction factor,
twos complement, 7 LSB/mgauss, 0x0000 = 0 mgauss
Hard Iron Factors
When the hard iron error estimation is complete, take the
following steps:
1. Multiply the estimate by −1 to change its polarity.
2. Convert it into digital format for the hard iron correction
registers (see Table 43).
3. Write the correction factors to the registers. For example,
lower the x-axis bias by 10 LSB (~1.429 mgauss) by setting
XMAGN_HIC = 0xFFF6 (DIN = 0xA7FF, 0xA6F6)
Soft Iron Effects
The XMAGN_SIC (see Table 46), YMAGN_SIC (see Table 47),
and ZMAGN_SIC (see Table 48) registers provide an adjust-
ment variable for the magnetometer sensitivity adjustment
in each magnetometer response to simplify the process of
performing a system level soft iron correction.
Table 46. XMAGN_SIC (Base Address = 0x2C), Read/Write
Bits
Description (Default = 0x8000)
[15:0] X-axis soft iron correction factor,
twos complement format, 1 LSB = 100%/32,767
0x7FFF = 100% increase (2×)
0x8000 = 100% decrease (0×)
Table 47. YMAGN_SIC (Base Address = 0x2E), Read/Write
Bits
Description (Default = 0x8000)
[15:0] Y-axis soft iron correction factor,
twos complement format, 1 LSB = 100%/32,767
0x7FFF = 100% increase (2×)
0x8000 = 100% decrease (0×)
Table 48. ZMAGN_SIC (Base Address = 0x30), Read/Write
Bits
Description (Default = 0x8000)
[15:0]
Z-axis soft iron correction factor,
twos complement format, 1 LSB = 100%/32,767
0x7FFF = 100% increase (2×)
0x8000 = 100% decrease (0×)
FLASH UPDATES
When using the user calibration registers to optimize system
level accuracy, set GLOB_CMD[3] = 1 (DIN = 0xBE04) to save
these settings in nonvolatile flash memory. Be sure to consider
the endurance rating of the flash memory when determining how
often to update the user correction factors in the flash memory.
RESTORING FACTORY CALIBRATION
Set GLOB_CMD[1] = 1 (DIN = 0xBE02) to execute the factory
calibration restore function, which resets the gyroscope and accel-
erometer offset registers to 0x0000 and all sensor data to 0. Then, it
automatically updates the flash memory and restarts sampling and
processing data. See Table 25 for information on GLOB_CMD.
Rev. B | Page 20 of 24