Modbus interface
Configuration section to select and configure the interface to be used for the modbus communication.
"Modbus interface" configuration section
| 1 | Selection of the interface to be used for the modbus communication | |
| off | Interface deactivated | |
| on | The RS485 interface should be used. | |
| 2 | Selection of the required baud rate | |
| 3 | Selection of the required stop bits | |
| 4 | Selection of the required parity | |
| 5 | Number of data bits to be used | |
| 6 | Time during which the modbus server must react to the command from the device | |
| 7 | Selection if the commands should be repeated when a communication error occurs | |
| Off | A communication error is highlighted immediately. | |
| 1-3 | When a communication error occurs, the relevant command is repeated x times. The error is only highlighted when the selected number of attempts has failed. | |
| 8 |
Number of measurement cycles for which the measurement value is held until the error value is issued |
|
| 9 | Activates the 120 Ω terminal resistance or RS485 A and B | |
| 10 | Activates the 390 Ω clamp resistances (pull up to RS485 A and pull down to RS485 B) | |
Example to explain the correlation between "Timeout", "Retry" and "Measurement interval"
| Basic setting |
|
Record interval | 5 min. |
|
Measurement cycle | 1 min. | |
| Modbus interface |
1st attempt |
Timeout | 4 sec. |
 Retry |
|||
| Retry | 1 |
Explanation: In this example 7 channels are activated, the modbus server however does not respond. At the time of measurement, there is an attempt to read the data for the modbus measurement channel 1. Since "Retry" is activated, there is another attempt to read the data for modbus measurement channel 1 after the "Timeout" has expired. After the "Timeout" has expired for the second time, the error code "OL" (Open Loop) is set for modbus measurement channel 1 and the first attempt to read the data for the modbus measurement channel 2 is started.
The number of activated channels (modbus measurement channels + modbus output channels), the "Timeout", the number of "Retry"s and the measurement cycle must hence be chosen as follows:
Retry not active: "Timeout" * no. of active channels < "Measurement cycle"
Retry active: "Timeout" * (1+ no. of retrys) * no. of active channels < "Measurement cycle"
