HP206C Datasheet, PDF (11/17 Pages) List of Unclassifed Manufacturers – PRECISION BAROMETER AND ALTIMETER SENSOR

DataSheet
HP206C
6.1 Setup the Altitude Offset Compensation Parameter
6.1.1 ALT_OFF_LSB, ALT_OFF_MSB - (RW)
The two registers form the 16-bit value of ALT_OFF, which saves the altitude offset data used to
compensate the altitude calculation. The data is in 2’s complement format and the unit is in centimeter. The
users need to set these registers if they need to use the altitude computation function of the device.
Normally, the values of the local average standard atmospheric pressure (P_local) may vary in different places
around the world. The varying range is from 1000 mbar to 1026 mbar. The device requires the user to setup
the ALT_OFF to remove the offset. The following table is provided to assist to finding the value of desired
altitude offset.
P_local has unit in mbar, Aoffset has unit in meter
P_local
1000
1001
1002
1003
A_offset
‐111.18 ‐102.73 ‐94.29 ‐85.85
P_local
A_offset
1004
‐77.43
1005
‐69.02
1006
‐60.62
1007
‐52.23
P_local
A_offset
1008
‐43.84
1009
‐35.47
1010
‐27.11
1011
‐18.76
P_local
A_offset
1012
‐10.41
1013
‐2.08
1014
6.24
1015
14.56
P_local
A_offset
1016
22.86
1017
31.15
1018
39.44
1019
47.71
P_local
A_offset
1020
55.98
1021
64.23
1022
72.48
1023
80.71
P_local
A_offset
1024
88.94
1025
97.16
1026
105.36
If the users find out that the value of P_local is an integer, they can directly obtain the corresponding altitude
offset value in the above table; if the P_local has decimal numbers and the value is larger than P1 and
smaller than P2 (P1 ^{and P2 are two adjacent pressure values in the table),} the user shall first obtain the
corresponding altitude offset value A1 and A2 in the table, than use either of the following two formulas
to calculate the desired altitude offset value A:
A = A₁ + 8.326 x (P_local – P₁), or ^{A = A}2 ^{- 8.326 x (P}2 ^{– P}local⁾
For example, the P_local is 1016.4 mbar, which is between ^{1016 mbar (P}1^{) and 1017 mbar (P}2^{). Looking up the table,}
A₁ is 22.86 m and A₂ is 31.15 m. Thus:
A = 22.86 + 8.326 x (1016.4 – 1016) = 26.19 m, or A = 31.15 - 8.326 x (1017 – 1016.4) = 26.15 m
Either of the results is acceptable. After obtaining the value of A, no matter by looking up the table
directly or by calculation, the user shall multiply the A by 100 in order to convert the unit from meter to
centimeter.
Finally, convert the result to a 2’s complement number to obtain ALT_OFF, and fill it into the two registers.
The following table shows 2 examples with the calculated altitude offsets and their corresponding values
to fill into the two registers.
HP206C_DataSheet_EN_V2.0
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