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<< Click to Display Table of Contents >> Navigation: Hardware Overview > Sensors and Probes > CCD-S > Modbus |
The probe can be addressed directly using the MODBUS protocol, to request the measured CO2 values. The parameters highlighted in yellow should be selected according to the table below.
Important: In order to communicate directly with the digital probe via MODBUS, please use the E2-05XX-MOD cable. The digital MODBUS protocol is delivered over RS485. |
Probe address |
Command ID |
Start address |
Number of records |
MODBUS CRC1 |
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0x00 |
0x04 |
0x00 |
0x00 |
0x00 |
0x00 |
0x0000 |
1 CRC calculation according to MODBUS standard
Probe address: 0…255, if '0' then all probes respond regardless of the address.
Start address |
Number of records |
Return values |
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|---|---|---|---|---|---|
0x00 |
0x04 |
Serial number |
CO2 |
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0x00000000 |
0x0000 |
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0x00 |
0x02 |
Serial number |
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0x00000000 |
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Probe address |
Command ID |
Number of data bytes |
Data (4…10 bytes) |
MODBUS CRC |
|---|---|---|---|---|
0x00 |
0x04 |
0x00 |
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 |
0x0000 |
Probe address |
Error code |
MODBUS CRC |
|
|---|---|---|---|
0x00 |
0x84 |
0x00 |
0x0000 |
Error codes |
|
|---|---|
0x02 |
Start address and number of records invalid |
0x03 |
Number of records invalid |
In the event of a short circuit or open circuit at the probe, a value of 19999 is output for the measured value concerned.
Primary tables |
Type |
Read / Write |
Coils / Registers |
Function code |
|
|---|---|---|---|---|---|
Coils |
Bit |
Read/Write |
1 … 9’999 |
0x01 |
Read Coils |
0x05 |
Write Single Coil |
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0x0F |
Write Multiple Coils |
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Discrete inputs |
Bit |
Read Only |
10’001 … 29’999 |
0x02 |
Read Discrete Inputs |
Input registers |
16-bit |
Read Only |
30’001 … 39’999 |
0x04 |
Read Input Register |
Holding registers |
16-bit |
Read/Write |
40’001 … 49’999 |
0x03 |
Read Holding Registers |
0x06 |
Write Single Register |
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0x10 |
Write Multiple Registers |
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Note: Coils and registers in Modbus are addressed starting at zero. Therefore coils numbered 1…16 are addressed as 0…15 or registers numbered (e.g. 10'001…10'016 are addressed as 10'000…10'015) |
Connection timeout: When TCP connection is open and for more than 30 seconds no communication is performed, the device automatically closes the TCP connection. In case of a communication interruption, this prevents the socket being blocked.
Additional MODBUS details can be found here: MODBUS in RMS.