Vaisala Hydromet Data Collection Platform User Manual
Page 172
User's Guide ______________________________________________________________________
170 _________________________________________________________________ M210933EN-C
An air pressure value of 991.9 hPa will then be compressed as follows:
1.
The value is first multiplied with the Multiplier value (10),
resulting in 9919 which in binary format is 10011010111111.
2.
The binary value is then divided into three separate 6-bit parts and
compressed to the three 8-bit ASCII-coded characters as follows:
a.
The 6 least significant bits: 111111 -> 00111111 = 63 = '?'
b.
Next 6 bits: 011010 -> 01011010 = 90 = 'Z'
c.
The remaining 2 bits: 000010 -> 01000010 = 66 = 'B'
d.
The string of characters representing the compressed data
value 991.9 is written as "BZ?" where the first character
includes the most significant bits.
The string "B_j" representing compressed data would be decompressed
as follows:
1.
First the 6-bit parts of each character are extracted as follows:
a.
'B' = 66 = 01000010 -> 000010
b.
'_' = 95 = 01011111 -> 011111
c.
'j' = 106 = 01101010 -> 101010
2.
As the last character includes the least significant bits, the resulting
binary number is 000010011111101010, which corresponds 10218
in the decimal format.
3.
The decimal number (10218) is divided with the pre-conversion
scale (10) resulting 1021.8 hPa as the measured air pressure value.
Example 2:
Configure the report as follows to compress the measured air
temperature value using the pseudo-binary format:
1.
Select the Signed value option, as the data may be either positive
or negative.
2.
Enter 10 as the Multiplier in order to include one decimal in the
compressed data.
3.
Use
as reference when entering the field
width value. In this case, enter 2 in the Field width box as the air
temperature value may vary between -50.0 °C and +80.0 °C, and
when the value is multiplied, the value to be compressed may vary
between -500 and +800.