E+E Elektronik EE872 Series, User Manual

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10
User Manual EE872 Modular Probe for CO
2
, RH, T and p
5.2.2 Modbus Register Map
The measured data is saved as 32 bit floating point values (data type FLOAT) and as 16 bit signed integer
values (data type INTEGER):
FLOAT 32 bit
Parameter Unit Register number
1)
[DEC] Protocol address
2)
[HEX]
Read register: function code 0x03 / 0x04
CO2 (average) ppm 1061 0x424
CO2 (raw) ppm 1063 0x426
Pressure p* mbar 1201 0x4B0
Pressure p* psi 1203 0x4B2
Relative humidity RH** % 1021 0x3FC
Temperature T** ° C 1003 0x3EA
Temperature T** ° F 1005 0x3EC
Temperature T** K 1009 0x3F0
Dew point temperature Td*** ° C 1105 0x450
Dew point temperature Td*** ° F 1107 0x452
Dew point temperature Td*** K 1147 0x47A
Tab. 2 Floating point values (read register)
INTEGER 16 bit
Parameter Unit Scale
3)
Register number
1)
[DEC] Protocol address
2)
[HEX]
Read register: function code 0x03 / 0x04
CO2 (average) ppm 1 4031 0xFBE
CO2 (raw) ppm 1 4032 0xFBF
Pressure p* mbar 10 4101 0x1004
Pressure p* psi 100 4102 0x1005
Relative humidity RH** % 100 4011 0xFAA
Temperature T** ° C 100 4002 0xFA1
Temperature T** ° F 50 4003 0xFA2
Temperature T** K 50 4005 0xFA4
Dew point temperature Td*** ° C 100 4053 0xFD4
Dew point temperature Td*** ° F 100 4054 0xFD5
Dew point temperature Td*** K 100 4074 0xFE9
Tab. 3 Integer values (read register)
*available for versions M13, M15
**available for version M13 only when probe is not heated (default setting)
***available for version M13 always: enabling or disabling the probe heating does not affect the Td measurement
1) Register number starts from 1.
2) Protocol address starts from 0.
3) Examples: For scale 100, the reading of 2550 means a value of 25.5. For scale 50, the reading of 2550 means a value of 51.
5.2.3 Reading Example
Example of MODBUS RTU command for reading the CO
2
(float value) CO
2
= 1288,34375 ppm
from the register 0x424:
Device EE872; slave ID 237 (0xED)
Reference document, chapter 6.3:
http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
Modbus ID
address
Function
code
Starting
address Hi
Starting
address Lo
No. of
register Hi
No. of
register Lo
CRC
Request [Hex]: ED 03 04 24 00 02 93 9C
Modbus ID
address
Function
code
Byte count Register 1
value Hi
Register 1
value Lo
Register 2
value Hi
Register 2
value Lo
CRC
Response [Hex]: ED 03 04 0B 00 44 A1 27 61