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5. Calculate the according gain and offset parameters from the recorded HCAL1 and HCAL2 values and the
desired VDAC1' and VDAC2' values using
G
16384
32768
=
+
OS
16384
VDAC1'
=
+
6. Programm the gain (G) and offset (OS) values into the sensor's EEPROM.
Attention: HCAL is a 16bit signed integer value in the range of ±30000. VDAC is a 12bit unsigned decimal
value applied to the internal DAC for the ratiometric output stage. The value range is from 0 to
4095 and corresponds to 0% to 100% of VDD..
6.2
Two-Point Calibration Examples
6.2.1
Calibration with Application Readout
Optimum accuracy of the TLE4997 can be achived by using a two-point calibration with readout of the HCAL
registers in the application. The sensor´s output register HCAL is measured at the end points of the applications
range of motion and derive the optimum offset and gain parameters from the desired VOUT values. The registers
can be read using the TLE4997 Evaluation Kit.
Example
An example application has a linear movement range from x
recorded.
In the application , it is desired to have the output value VOUT1' = 0.25V (5% of the full 5V range) at position x
and VOUT2' = 4.75V (95% of full 5V range ) at position x
The measured HCAL and desired VOUT' values are shown in
Table 6-1
Example VOUT and HCAL values for 2-point calibration
Position
measured
HCAL (Hex)
x
EAC5
1
H
x
183B
2
H
Applying the HCAL and VDAC' values form
G
16384
32768
=
+
OS
16384
205-
=
+
This corresponds to a multiplicative gain of 2.53 and an offset of 2.35V, according to the formulas in
Attention: If the measured HCAL values are close to the range limits ±30000, saturation takes place. In this
case, it is recommended to switch to a higher magnetic range (±100 or ±200 mT) prior to the
calibration.
User's Manual
Equation (6.2)
VDAC2' VDAC1'
–
⋅
-------------------------------------------------- -
HCAL2 HCAL1
–
(
) HCAL1
⋅
G 16384
–
------------------------------------------------------ -
–
32768
HCAL (Dec, signed)
Range ±30000
-5435
6203
Table 6-1
(
)
3890 205
–
⋅
------------------------------------------
(
– (
)
)
6203
5435
–
(
)
⋅
– (
26759 16384
–
---------------------------------------------------------------- -
32768
Calibration of TLE4997 Output Characteristic
and
Equation
to x
. In both positions , the register value HCAL is
1
2
.
2
Table 6-1
desired
VOUT' (V)
0.25
4.75
in
Equation (6.2)
26759
=
)
5435
18310
=
35
User's Manual
(6.3).
desired
VDAC' (Dec)
VDAC'(Hex)
Range 0 to 4095
CD
205
H
F32
3890
H
and
Equation (6.3)
yields:
TLE4997
(6.2)
(6.3)
1
(6.4)
(6.5)
Chapter
4.
v01_01, 2019-08
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