ADIS16488 datasheet(23/36 Pages) AD

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Data Sheet

ADIS16488

Rev. B | Page 23 of 36

CALIBRATION

The ADIS16488 factory calibration produces correction formulas

for the gyroscopes, accelerometers, magnetometers, and

barometers, and then programs them into the flash memory.

In addition, there are a series of user-configurable calibration

registers, for in-system tuning.

GYROSCOPES

The user-calibration for the gyroscopes includes registers for

adjusting bias and sensitivity, as shown in Figure 22.

X-AXIS

GYRO

FACTORY

CALIBRATION

AND

FILTERING

X_GYRO_OUT

X_GYRO_LOW

XG_BIAS_HIGH

XG_BIAS_LOW

1 + X_GYRO_SCALE

Figure 22. User Calibration Signal Path, Gyroscopes

Manual Bias Correction

The xG_BIAS_HIGH registers (see Table 64, Table 65, and

Table 66) and xG_BIAS_LOW registers (see Table 67, Table 68,

and Table 69) provide a bias adjustment function for the output

of each gyroscope sensor.

Table 64. XG_BIAS_HIGH (Page 2, Base Address = 0x12)

Bits

Description (Default = 0x0000)

[15:0]

X-axis gyroscope offset correction, upper word

twos complement, 0°/sec = 0x0000, 1 LSB = 0.02°/sec

Table 65. YG_BIAS_HIGH (Page 2, Base Address = 0x16)

Bits

Description (Default = 0x0000)

[15:0]

Y-axis gyroscope offset correction, upper word;

twos complement, 0°/sec = 0x0000, 1 LSB = 0.02°/sec

Table 66. ZG_BIAS_HIGH (Page 2, Base Address = 0x1A)

Bits

Description (Default = 0x0000)

[15:0]

Z-axis gyroscope offset correction, upper word;

twos complement, 0°/sec = 0x0000, 1 LSB = 0.02°/sec

Table 67. XG_BIAS_LOW (Page 2, Base Address = 0x10)

Bits

Description (Default = 0x0000)

[15:0]

X-axis gyroscope offset correction, lower word;

twos complement, 0°/sec = 0x0000,

1 LSB = 0.02°/sec ÷ 216 = ~0.000000305°/sec

Table 68. YG_BIAS_LOW (Page 2, Base Address = 0x14)

Bits

Description (Default = 0x0000)

[15:0]

Y-axis gyroscope offset correction, lower word;

twos complement, 0°/sec = 0x0000,

1 LSB = 0.02°/sec ÷ 216 = ~0.000000305°/sec

Table 69. ZG_BIAS_LOW (Page 2, Base Address = 0x18)

Bits

Description (Default = 0x0000)

[15:0]

Z-axis gyroscope offset correction, lower word

twos complement, 0°/sec = 0x0000,

1 LSB = 0.02°/sec ÷ 216 = ~0.000000305°/sec

Bias Null Command

The continuous bias estimator (CBE) accumulates and

averages data in a 64-sample FIFO. The average time (tA)

for the bias estimates relies on the sample time base setting in

NULL_CNFG[3:0] (see Table 70). Users can load the correction

factors of the CBE into the gyroscope offset correction registers

(see Table 64, Table 65, Table 66, Table 67, Table 68, and Table 69)

using the bias null command in GLOB_CMD[0] (see Table 114).

NULL_CNFG[13:8] provide on/off controls for the sensors that

update when issuing a bias null command. The factory default

configuration for NULL_CNFG enables the bias null command

for the gyroscopes, disables the bias null command for the accel-

erometers, and establishes the average time to ~26.64 seconds.

Table 70. NULL_CNFG (Page 3, Base Address = 0x0E)

Bits

Description (Default = 0x070A)

[15:14]

Not used

Z-axis acceleration bias correction enable (1 = enabled)

Y-axis acceleration bias correction enable (1 = enabled)

X-axis acceleration bias correction enable (1 = enabled)

Z-axis gyroscope bias correction enable (1 = enabled)

Y-axis gyroscope bias correction enable (1 = enabled)

X-axis gyroscope bias correction enable (1 = enabled)

[7:4]

Not used

[3:0]

Time base control (TBC), range: 0 to 13 (default = 10);

tB = 2TBC/2460, time base,

tA = 64 × tB, average time

Turn to Page 3 (DIN = 0x8003) and set GLOB_CMD[0] = 1

(DIN = 0x8201, then DIN = 0x8300) to update the user offset

registers with the correction factors of the CBE. Make sure that the

inertial platform is stable during the entire average time for optimal

bias estimates.

Manual Sensitivity Correction

The x_GYRO_SCALE registers enable sensitivity adjustment

(see Table 71, Table 72, and Table 73).

Table 71. X_GYRO_SCALE (Page 2, Base Address = 0x04)

Bits

Description (Default = 0x0000)

[15:0]

X-axis gyroscope scale correction; twos complement,

0x0000 = unity gain, 1 LSB = 1 ÷ 215 = ~0.0003052%

Table 72. Y_GYRO_SCALE (Page 2, Base Address = 0x06)

Bits

Description (Default = 0x0000)

[15:0]

Y-axis gyroscope scale correction; twos complement,

0x0000 = unity gain, 1 LSB = 1 ÷ 215 = ~0.0003052%

Table 73. Z_GYRO_SCALE (Page 2, Base Address = 0x08)

Bits

Description (Default = 0x0000)

[15:0]

Z-axis gyroscope scale correction; twos complement,

0x0000 = unity gain, 1 LSB = 1 ÷ 215 = ~0.0003052%

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