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by anonymous
Hi to all... I can't find previous question I made about this, I hope to not post same question twice.

I need RUT955 alerts me when battery goes down, the same when battery level backs to normal voltage.
I set input/output but analog readings gives +/- 0.02V tolerance, so if I set 12.50V as threshold I continuously get alerts by SMS or mail when voltage is around 12.5V value.
I am asking about set an hysteresis...

For the while I made in this way:

- OUTPUT4_OFF = when Output4 low
- OUTPUT4_ON = when Output4 high

- Send mail battery low
- Send mail battery ok
- OUTPUT4_ACTIVE = maintain, Output (4) set high, condition OUTPUT4_OFF
- OUTPUT4_IDLE = maintain, Output (4) set low, condition OUTPUT4_ON


- Analog input (6,9) = inside 0.5-11.8 range, actions "send mail battery low" and OUTPUT4_ACTIVE, conditions OUTPUT4_OFF

- Analog input (6,9) = inside 12.3-15.0 range, actions "send mail battery ok" and OUTPUT4_IDLE, conditions OUTPUT4_ON

This works but I need to use output 4 as hardware flag, so I can't use relays previously connected to output4.
Is there a smartest solution?

1 Answer

0 votes
by anonymous



Could you clarify what you are using the digital output for?

Generally, I would recommend configuring Modbus Alarms here. This way, the device would read its Modbus registers continuously every x amount of seconds, and if the values match the specified condition (voltage low), it can:

  • Perform a Modbus write request to the RUT955 or any other Slave device;
  • Send an MQTT message;
  • Trigger any I/O output;
  • Send an SMS;
The main advantage of doing it this way is that the Modbus Alarms also include options for Action frequency and Redundancy protection. Action frequency specifies whether the action needs to be executed every time the condition is satisfied, or only the first time. Redundancy protection will help alleviate any undesirable duplicate messages for a specified amount of time (e.g. don't send the message for the first 200 seconds).

To configure it, you'll first need to enable the Modbus TCP Slave by navigating to Services → Modbus → Modbus TCP Slave. Once it's enabled, open the Modbus TCP Master settings. Add a new slave device. Once the advanced configuration window opens up, enable the instance, enter a name, IP address (, and the period of how often the voltage should be checked.

Once that is done, scroll down to the bottom to the alarms configuration and create a new instance

  • Enable the instance;
  • Select the function as Read Holding Registers (3);
  • Compared condition data type as 32bit UINT, Byte order 1,2,3,4;
  • First register number as 142 (full list of Modbus registers of RUT955 can be found here);
  • In the Values field, specify 12 or 13 (voltage)(this field does not allow floating numbers);
  • Select the condition as Less than (if the voltage is lower than 12);
  • Action frequency should be set to First trigger;
  • Enable the redundancy protection and specify the time in seconds to delay the action;
  • Select the action you'd like to perform when the condition is specified;

Multiple alarms can be configured with the same condition if needed (e.g. set the I/O pin and send an SMS). Once configured, everything should function as expected.

Let me know if any additional information is needed!


Best regards,