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TLE5014
GMR-Based Angle Sensor
Initial Calibration
8
Initial Calibration
This chapter describes which initial calibration has to be performed with the TLE5014.
8.1
Zero Angle Calibration
The zero angle (or angle base) is stored in the bits [15:3] of address 0x00A0 of the EEPROM as a 14-bit value (see
Description EEPROM Address 0x00A0
In the application, the angle base has to be programmed by the customer.
The following procedure for angle base calibration is recommended (external reference required):
1. Measure the angle value of several reference points (e.g. ≥ 16) over a full rotation. A fixed distance between
the reference points is not necessary
2. Calculate the angle difference between each reference point (ideal position) and the corresponding
measured angle value
3. Calculate the arithmetical mean value of these angle differences to get the overall angle offset error
4. Calculation of ANG_BASE parameter:
•
If angle values were read out with SICI:
shift right by 1 bit resp. round angle values to 14 bit
•
If angle values were read out with SPC/SENT/PWM:
shift left angle values by 2 bits, i.e. multiply by 4 (i.e. scale to 14bit)
5. Shift left ANG_BASE by 2 bits and OR it with desired ANG_DIR setting
6. Write resulting word into ANG_BASE line in EEPROM
8.2
Look-up Table Calibration
The sensor has a 32 point look-up table (LUT) implemented. With the help of the look-up table it is possible to
do an additional end-of-line calibration and reduce non-linearities resulting from a non perfect magnetic
circuit (e.g. assembly tolerances as tilt and/or eccentricity). For this, an external reference is required and the
sensor output at defined angle positions has to be measured.
The following procedure is recommended for look-up- table calibration:
1. Measure the angle values on the 32 equidistant distributed reference points over 360° (0°, 11.25°, 22.5°,...)
2. Calculate 16bit look-up table value (LUT[LSB
[
LUT LSB 16
POSITION[LSB
]: 16bit reference angle
16
readout[LSB12]: 12bit angle value at reference position
3. If difference is negative or ≥ 2
to cutting of the overflow bits resp. is implicitly done, if the calculation is done in pure 16 bit
4. Write each of the 16-bit LUT values into the corresponding reference point's index in the LUT
5. The 8-bit CRC calculated over the written LUT values has to be written into the address 0x00F0, bits [7:0]
(see
Description EEPROM Address 0x00F0
In case the look-up table is used for sensor output linearization, the angle base (angle offset) has to be
corrected first by programming the angle base register 0x00A0. After defining the correction values for the
look-up table, the angle base shall not be changed as this will introduce additional angle error.
User's Manual
ANG_BASE). The sensor output angle is in reference to this angle base.
]
⋅
=
2 POSITION LSB 16
16
: add/subtract 2
CRC_LUT)
(Description EEPROM Address 0x00A0
])according to the equation below:.
16
[
]
(
–
16 readout LSB 12
16
so that the result is within 0 and 2
42
ANG_BASE)
⋅
[
16
-1. This is equivalent
(Table
]
)
10)
Rev. 1.0
2019-03-12
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