Reading The Gas Concentration - Dräger Polytron 8000 Series Technical Manual

Integration into process control systems
Changing passwords
There are 2 parameters for changing passwords. Both parameters are 4 registers
long. In the first two registers, the current password is requested, and in the other
two registers, the new password is set.
Password
Calibration PWD
Settings PWD
Checking the password changes
The PASSWORD_STATUS parameter can be used to check whether the
passwords were changed successfully. The parameter is one register long (register
40709) and can assume the following values.
Parameter values
0000
0x00
0x02
0x05
The following subsections present telegrams for reading and/or writing based on
the corresponding key parameters of the gas detector.
5.2

Reading the gas concentration

The MEASUREMENT_MODE parameter indicates the current value of the gas
concentration and can be read cyclically via the register address 40507. The
parameter is read-only and is updated each second by the gas detector.
Bit15 Bit14 Bit13 Bit12 Bit11 Bit10 Bit09 Bit08 Bit07 Bit06 Bit05 Bit04 Bit03 Bit02 Bit01 Bit00
MEASUREMENT_MODE.VALUE[3]
E.g.: MEASUREMENT_MODE.VALUE=40.00 (dec) / 0x42200000 (hex)
0x42
Bit15 Bit14 Bit13 Bit12 Bit11 Bit10 Bit09 Bit08 Bit07 Bit06 Bit05 Bit04 Bit03 Bit02 Bit01 Bit00
MEASUREMENT_MODE.VALUE[1]
E.g.: MEASUREMENT_MODE.VALUE=40.00 (dec) / 0x42200000 (hex)
0x00
The corresponding telegram from the master for reading the
MEASUREMENT_MODE parameter is shown in the following table. The parameter
is read using the Modbus function code 0x03 - Read Holding Registers. In addition,
the master needs the address of the gas detector and the register address for
successful communication.
Slave address Function code
0x03
28
Parameter
SET_CAL_PASSWORD
SET_CFG_PASSWORD
Meaning
Successfully changed
Error
Incorrect selection
Too few bytes
Register: 40507
Register: 40508
Register address -1
0x03 0x01
0xFA
Technical Manual
Register
40705 - 40708
40701 - 40704
MEASUREMENT_MODE.VALUE[2]
0x20
MEASUREMENT_MODE.VALUE[0]
0x00
Number of regis-
ters
0x00
0x02
|
Digital Communication - Modbus RTU
CRC
0x24
0xE4