HMI trends, recipes and user management
Trends and data logging on panels, recipe handling between HMI and PLC, user levels and audit — what to configure and what to watch out for.
Trends and logging
- Online trends show values from the runtime buffer — fine for watching a startup.
- Historical trends need data logs on the panel (SD card, internal memory) or a historian. Define for each logged tag: sampling (cyclic or on change), deadband, retention period, storage size.
- Panel storage is limited and fails silently when full — check rotation settings and back up logs, or move history to SCADA/historian.
Recipes
A recipe is a named set of parameters (temperatures, times, speeds) for one product. Two patterns:
| Pattern | Data stored in | Notes |
|---|---|---|
| HMI recipes | Panel memory / files | Easy editing; download to PLC must be consistent (all values in one transfer + handshake) |
| PLC recipes | PLC data blocks / arrays | Survive panel replacement; HMI only selects and edits |
Always confirm a recipe download with a handshake: the PLC accepts the data set only when the equipment is in a state where parameters may change.
User management
- Define roles, not individuals: operator, shift leader, maintenance, engineer, administrator.
- Assign each critical action (setpoint change, mode change, bypass, recipe edit) a minimum level.
- Automatic logoff after inactivity; no shared generic accounts for critical actions.
- In regulated industries (pharma, food) changes must be traceable: user, time, old and new value — an audit trail.
- Central user management (e.g. directory integration) simplifies large plants.
Connections
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Sources
Updated 2026-10-02