Hermetry has three tools that act on device data: alarm rules on device profiles, the Rules card on dashboards, and flows. They share the same alarms, the same commands and the same notifications. Pick the simplest one that does the job.
Which tool to use
| You want to | Use | Where you set it |
|---|---|---|
| Open an alarm when a value crosses a limit, and close it when it is back | An alarm rule | The device profile’s Alarm rules tab. One rule covers every device of the profile. |
| Open an alarm when a device goes offline | A Device offline rule | The same tab. |
| Do something when something happens: switch a fan, change a setting, tell people, wait, branch | A rule in the Rules card | A Rules card on a dashboard, for one site, building, room or device. |
| Work by the clock or the calendar: at 07:00 on weekdays, at sunset, on public holidays | A rule in the Rules card | The same card. |
| Transform, enrich or route messages, compute derived values, call outside systems | A flow | Automation. See Flows. |
Rules of thumb:
- If the answer is “an alarm”, start with an alarm rule. Debounce, hysteresis, dampening, reminders and the storm guard are built in.
- If the answer is “do something”, use the Rules card. Every rule is a flow behind the scenes, but you never draw it.
- If neither fits, use a flow. A Rules-card rule can be detached into an ordinary flow when it outgrows the card.
| Alarm rule | Rules card | Flow | |
|---|---|---|---|
| Set per | Device profile | Place (asset or device) | Organisation |
| Compares with | Fixed values or a device attribute | Fixed values, or a formula over stored values | Anything a block can compute |
| Acts | Opens, escalates and clears one alarm | Commands, settings, notifications, alarms, waits, other rules | Every block |
| Who may change it | Admin | Admin | Admin |
| Stopped by Manual mode | No | Yes | No |
How device data reaches them
- A device sends a message.
- The organisation’s root flow runs for it (or the root flow of the device’s profile, if it has one). By default it saves telemetry, saves client attributes and evaluates the alarm rules of the device’s profile.
- After a value is stored, the Rules-card rules that watch it receive it.
- Alarm changes go to the bell, notifications, webhooks, dashboards, Rules-card rules and flows.
Note
Only flows store data. A message that no flow saves is not stored, and alarm rules see only what the root flow passes to them. Do not remove the save and alarm steps from a root flow unless you mean it. See Hosts, the root flow and profile root flows.
In this section
Alarms
- Alarms: severities, statuses, lifecycle, history
- Working with alarms: the Alarms page, acknowledge, clear, notes
- Muting a device for maintenance
- Alarm rules on device profiles
- Alarm conditions reference
- Debounce, hysteresis and dampening
- Offline alarms
- Clear conditions and late readings
- Alarm rule cookbook
The Rules card
- The Rules card: overview, home, writing and testing a rule
- Rules card: triggers (“When”)
- Rules card: conditions (“Only if”)
- Rules card: actions (“Then”)
- Time, sunrise/sunset, dates and holidays
- Manual and Auto modes
- Rules card cookbook
Related
- Flows and Notifications: short overviews that lead to their own sections
- Troubleshooting rules and alarms