Monitor temperature and trigger an alarm

The scenario: a cold storage facility has sensors in several rooms. You want to see the temperature on a dashboard and get an alarm when the inlet temperature goes above 23.5 °C.

Prerequisites: the workspace, the channel warehouse-telemetry, and the devices have been created and connected (publish), and a storage rule is in place. If not, follow the Quick start.

1. Send data

The device (or the simulator) sends SenML every few seconds:

[{"bn":"room-a1:","n":"temp_inlet","u":"Cel","v":22.4},
 {"n":"temp_outlet","u":"Cel","v":33.7},
 {"n":"humidity","u":"%RH","v":48.3},
 {"n":"power_draw","u":"W","v":1128.3}]

In Messages, the metric name is stored as room-a1:temp_inlet. If you use SenML without bn, the name is just temp_inlet.

2. Build the alarm rule

In Automation → Rules → Create rule, build:

Channel Subscriber → Lua → Alarm.

1. Add Input: Channel Subscriber, pick the channel Warehouse Telemetry, and leave the subtopic empty.

2. Add Logic: Lua code, paste the code below. It returns an alarm object when the temperature exceeds the limit, or false when it is normal.

   function logicFunction()
     for _, rec in ipairs(message.payload) do
       if rec.n and string.find(rec.n, "temp_inlet$") and rec.v and rec.v > 23.5 then
         return {
           severity    = 70,
           cause       = "Inlet temperature above limit",
           measurement = rec.n,
           value       = rec.v,
           unit        = "Cel",
           threshold   = "23.5",
         }
       end
     end
     return false
   end
   return logicFunction()

3. Add Output: Alarm. Leave the fields empty (they are taken from the Lua result). Set auto-clear: after N consecutive normal messages, for example 3.

4. Save the rule with the name High inlet temperature alarm, then turn on the Rule enabled switch.

Without code

For a simple condition, use a Comparison node (message.payload[1].v >= number 23.5) in front of the Alarm output, with the alarm fields filled in through templates. Lua is used here because the metric name contains a source prefix.

3. Test with Test Rule

Click Test Rule and enter a sample payload. The logic really runs; the Alarm output only shows a preview, so no real alarm is created.

4. See and handle the alarm

When the temperature crosses 23.5 °C, an alarm appears in the Alarms menu, on the Home card, and in the bell in the top bar.

• Later readings that stay high do not create a new alarm: the occurrence counter increases (deduplication per rule, device, and measurement).
• After 3 consecutive normal messages, the alarm becomes cleared automatically.
• You can Acknowledge, Assign to a colleague, write a comment, or Resolve manually.

5. Notifications

On the Alarms page, set the workspace notifications: in-app, e-mail, and Telegram, with a minimum severity (60 by default). The Send test notification button makes sure a channel works. The severity-70 alarm in this example (High) meets the default threshold.

6. Show it on a dashboard

Add an Alarm Table widget and a Count Card (the alarms entity) to your dashboard, together with a temp_inlet chart per room (Dashboards).

Variations

Need	How
An alarm only when high for 5 minutes	Use a scheduled rule with query_agg("room-a1:temp_inlet", "5m", "min") > 23.5, then an Alarm output (Scheduled rules).
Also send to Telegram	Add a Telegram output on the same logic; the template uses {{.Result.cause}} and {{.Result.value}}.
An alarm per room	Use measurement = rec.n (as in the example) so each room has its own alarm.