SENTRON A120-001, Technical Manual, Page: 7 / 12

7
Data communication
Before connecting and powering up the modules in your embedded environment or to the computer make sure the all the necessary module are connected to
each other and correct baud rate of 115k2 8N1 is set. See chapter 3 for power and data pins on the AD converter module when the USB interface is not connected
and the communication is directly to the AD converter.
5.1 Protocol
A command is sent to the device in the form of ASCII characters, and the return string is received as a series of bytes representing 6-bit binary decimals. The
return bytes will need to be decoded into a measurement value through a calculation. The method of decoding is shown in the table below.
1 Dummy bytes
2 Response time is depending on signal stability, maximum at 120 seconds
3 Use function after desired number of calibration points is achieved
4 Separation bytes
5 Shown numbers are separate bytes, not characters.
Function
Send ASCII command
(bytes)
Decode calculation.
Multiply or add decimal
byte position value.
Units
A B C D
1
E
1
F
1
G
1
H
1
I
1
J K
A*4096+B*64+C 0.001 pH
byte byte byte 000 000 000 000 000 000 013 010
A B C
1
D
1
E
1
F G A*64+B 0.1 ° F
byte byte 000 000 255 013 010
Start Calibration
CLR!<CR>
(067 076 082 033 013)
082 013 013
Calibration pH 2
111!<CR>
5
(001 001 001 033 013)
001 013 010
2
Calibration pH 4
112!<CR>
5
(001 001 002 033 013)
002 013 010
2
Calibration pH 7
113!<CR>
5
(001 001 003 033 013)
003 013 010
2
Calibration pH 10
114!<CR>
5
(001 001 004 033 013)
004 013 010
2
Calibration pH 12
115!<CR>
5
(001 001 005 033 013)
005 013 010
2
End calibration
3
QIT!<CR>
(081 073 084 033 013)
084 013 010
000!<CR>
(048 048 048 033 013)
ABCDEFGHIJKLMN 013 010 A
4
B C D
4
E F G
4
H I J
4
K L M N
001 byte byte Slope pH 2-4 = B*64+C 0.1 %
002 byte byte Slope pH 4-7 = E*64+F 0.1 %
003 byte byte Slope pH 7-10 = H*64+I 0.1 %
004 byte byte 013 010 Slope pH 10-12 = K*64+L 0.1 %
Receive bytes from AD Converter or USB Interface.
Retrieve slope
Decimal bytes return
ABCDEFG 013 010
777!<CR>
(055 055 055 033 013)
Retrieve temperature
ABCDEFGHIJK 013 010
999!<CR>
(057 057 057 033 013)
Retrieve pH value