9
User Manual EE072 Humidity and Temperature Probe with Modbus RTU
INTEGER (read register):
Parameter
Unit
Scale
3)
Register number
1)
[Dec] Register address
2)
[HEX]
Read register: function code 0x03 / 0x04
Temperature T
°C
100
4002
0xFA1
Temperature T
°F
50
4003
0xFA2
Temperature T
°K
50
4005
0xFA4
Relative humidity RH, Uw
% RH
100
4011
0xFAA
Water vapour partial pressure e
mbar
10
4051
0xFD2
Water vapour partial pressure e
psi
1000
4052
0xFD3
Dew point temperature Td
°C
100
4053
0xFD4
Dew point temperature Td
°F
100
4054
0xFD5
Dew point temperature Td
°K
100
4074
0xFE9
Wet bulb temperature Tw
°C
100
4055
0xFD6
Wet bulb temperature Tw
°F
100
4056
0xFD7
Wet bulb temperature Tw
°K
100
4073
0xFE8
Absolute humidity dv
g/m³
10
4057
0xFD8
Absolute humidity dv
gr/ft³
10
4058
0xFD9
Mixing ratio r
g/kg
10
4061
0xFDC
Mixing ratio r
g/lb
10
4062
0xFDD
Specific enthalpy h
kJ/kg
1
4063
0xFDE
Specific enthalpy h
ft lbf/lb/kg
1
4064
0xFDF
Specific enthalpy h
BTU/lb
1
4065
0xFE0
Frost point temperature Tf
°C
100
4066
0xFE1
Frost point temperature Tf
°F
100
4067
0xFE2
Frost point temperature Tf
°K
100
4075
0xFEA
Ice bulb temperature Ti
°C
100
4119
0x1016
Ice bulb temperature Ti
°F
100
4120
0x1017
Ice bulb temperature Ti
°K
50
4121
0x1018
1) Register number starts from 1
2) Register 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.
5.3 Modbus RTU Example
Example of MODBUS RTU command for reading the temperature (float value) T = 26,953624 °C
from the register 0x3EA
•
Device EE072; slave ID 234 [0xEA]
Reference document, chapter 6.3:
www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
• See Application Note Modbus AN0103 (available on
)
Modbus ID
address
Function
code
Starting
address Hi
Starting
address Lo
No. of
register Hi
No. of
register Lo
CRC
Request [Hex]:
EA
03
03
EA
00
02
F2
A0
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]:
EA
03
04
A1
06
41
D7
12 CE
Decoding of floating point values:
Floating point values are stored according IEEE754 standard. The byte pairs 1, 2 and 3, 4 are inverted
as follows:
MMMMMMMM
MMMMMMMM
SEEEEEEE
EMMMMMMM
Byte 3
Byte 4
Byte 1
Byte 2
Example:
Response [Hex]
Value in
decimal
Byte 1 (Register 2 - Hi) Byte 2 (Register 2 - Lo) Byte 3 (Register 1 - Hi) Byte 4 (Register 1 - Lo)
41
D7
A1
06
26.953624
