User manual

OPERATION MANUAL
Technical changes reserved
0141 0316-196 27.08.2015
Humidity- temperature probe
with USB-Interface
Format of Data transfer
The USB-port works as a so-called COM-Port emulation and from a
programmer‘s point of view, it behaves like a serial interface.
The transfer of useful data takes place in lines. All characters are
ASCII coded. All information is sent continuously without separation
characters. In one line, only information of one channel is transfer-
red. At the end of the line, the last two ASCII characters are sent for
the check sum(CRC) of the current line. Each line closes with the
character ‘Carriage return’ ‘<CR>´. Several lines form a data-block. A
data-block can have the following contents, for example:
@<CR>
I01010100B00725030178<CR>
V010892A1<CR>
I02020100B00725030148<CR>
V0216B0EA<CR>
$<CR>
The data block has a following structure:
• A synchronization pattern for the beginning of a Data block. For
synchronization, the sequence ´@ <CR>´ is used.
• The conguration data (´Identier´) of a channel. The data line
begins with the character ‘I’, followed by the logical channel
number, and then followed by conguration data and the sensor
serial number. The line is closed with the check sum and the
character ‘<CR>’.
• The measured values of a channel. The data line begins with the
character ´V´, followed by the logical channel number, followed
by useful data. Only numerical measurement values and the
check sum (CRC) at the end of the line, are transferred. All other
information like number format, number of characters, physical
unit, etc. are contained in the conguration data (probe code).
• The conguration data and measurement values follow the same
scheme for all other channels.
• The continuation character ´$´ <CR>´ is sent at the end of a
data-block.
Structure of conguration data line
• The conguration data line contains all infor-mation of the sensor
working on the corre-sponding channel. The line has a following
structure:
• Identication character ´I´ at the beginning of the line.
• 8 bits (two ASCII characters) logical channel number. The logical
channel number is used to co-relate conguration data with the
measured values. In the Humidity-Temperature module, the tem-
perature values are transmitted through channel 01 and humidity
values are transmitted through channel 02.
• 8 bits (two ASCII characters) physical probe coding. Based on
probe coding, the number format, scale, physical unit and allo-
wable range of values are specied. For the described device,
probe coding is 01 for temperature channel and 02 for humidity
channel.
• 8 bits (two ASCII characters) hardware coding (type of the
measurement probe). The Tem-perature/Humidity module has
the code num-ber 01.
• 48 bits (twelve ASCII characters) serial number of the sensor.
Each serial number is allotted only once.
• 8 bits (two ASCII characters) CRC (check sum)
• ´<CR>´ as line termination
Structure of measured value data lines
The measured value data line contains the current measurements of
the sensor operating on the corresponding channel. All information
is represented in binary and is transferred in ASCII coded format
without separation characters. For the probe code 01, the line has
following a structure:
• Identication character ´V´ at the beginning of the line
• 8 bits (two ASCII characters) logical channel number (01 for
temperature, 02 for humidity)
• 2 Byte (4 ASCII-characters) measurement data. For the
temperature with 0.01°C resolu-tion. The hexadecimal value is
to be converted into a decimal number and to be divided by
100. With this, the temperature value is ob-tained in °C with
two decimals. For humidity value with 0.005 % resolution. The
hexadecimal value is to be converted into a decimal number and
to be divided by 200. With this, the relative humidity rH value is
ob-tained in % with two decimals.
• 8 bits (two ASCII characters) check sum (CRC)
• ´ <CR>´ as line termination
In the example given in opposite column, the measured temperature
is equal to 21.94° C and humidity of air is 29.04 % RH.
Humidity- temperature probe
with USB-Interface
B+B Thermo-Technik GmbH | Heinrich-Hertz-Straße 4 | D-78166 Donaueschingen
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