HAL800 Datasheet, PDF (10/24 Pages) Micronas – Programmable Linear Hall Effect Sensor

HAL 800
2.3.2. Calibration of Angle Sensor
The following description explains the calibration pro-
cedure using an angle sensor as an example. The
required output characteristic is shown in Fig. 2–8.
– the angle range is from −25° to 25°
– temperature coefficient of the magnet: −500 ppm/K
Step 1: Input of the registers which need not to be
adjusted individually
The register values for the following registers are given
for all applications:
– FILTER
Select the filter frequency: 500 Hz
– RANGE
Select the magnetic field range: 30 mT
– TC
For this magnetic material: 1
– TCSQ
For this magnetic material: 12
– CLAMP-LOW
For our example: 0.5 V
– CLAMP-HIGH
For our example: 4.5 V
Enter these values in the software, and use the
“WRITE” command for writing the values in the regis-
ters.
Step 2: Calculation of V_OQ and Sensitivity
There are 2 ways to calculate the values for V_OQ and
Sensitivity
Manual Calculation:
Set the system to calibration point 1 (angle 1 = −25°)
and read the register ADC-READOUT. For our exam-
ple, the result is ADC-READOUT1 = −2500.
Now, set the system to calibration point 2 (angle 2 =
25°), and read the register ADC-READOUT again. For
our example, the result is ADC-READOUT2 = +2350.
With these measurements and the targets V_OUT1 =
4.5 V and V_OUT2 = 0.5 V, the values for Sensitivity and
V_OQ are
Sensitivity =
4.5 V − 0.5 V
−2500 − 2350
2048
* _{5 V} = −0.3378
V_OQ = 4.5 V −
−2500 * (−0.3378) * 5 V _{= 2.438 V}
2048
V
5
V_{OUT 4}
Clamp-high = 4.5 V
Calibration point 1
3
2
1
Clamp-low = 0.5 V
Calibration point 2
0
–30 –20 –10 0 10 20 30 °
Angle
Fig. 2–8: Example for output characteristics
This calculation has to be done individually for each
sensor.
Automatic Calibration:
Use the menu CALIBRATE from the PC software and
enter the values 4.5 V for V_OUT1 and 0.5 V for V_OUT2.
Set the system to calibration point 1 (angle 1 = −25°),
hit the button Read ADC-Readout1, set the system to
calibration point 2 (angle 2 = 25°), hit the button Read
ADC-Readout2, and hit the button Calculate. The soft-
ware will then calculate the appropriate V_OQ and Sen-
sitivity.
Now, write the calculated values into the HAL 800 for
programming the sensor and use the “STORE” com-
mand for permanently storing the EEPROM registers.
Step 3: Locking the Sensor
The last step is activating the LOCK function with the
“LOCK” command. The sensor is now locked and does
not respond to any programming or reading com-
mands.
Warning: This register cannot be reset!
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