Signal Data Model¶

The SHM backend organizes monitoring signal metadata into two parallel hierarchies: main signals and derived signals.

Main Signal Hierarchy¶

erDiagram
    Signal ||--o{ SignalHistory : "has many"
    Signal ||--o{ SignalCalibration : "has many"

    Signal {
        int id PK
        string signal_name
        int subassembly_id FK
        string direction
    }

    SignalHistory {
        int id PK
        int signal_id FK
        datetime time
        string status
        int sensor_serial_number
    }

    SignalCalibration {
        int id PK
        int signal_id FK
        datetime time
        float offset
        float cwl
    }

Derived Signal Hierarchy¶

erDiagram
    DerivedSignal ||--o{ DerivedSignalHistory : "has many"
    DerivedSignal ||--o{ DerivedSignalCalibration : "has many"
    DerivedSignal }o--o{ Signal : "parent signals"

    DerivedSignal {
        int id PK
        string signal_name
        int subassembly_id FK
        string source_name
    }

    DerivedSignalHistory {
        int id PK
        int derived_signal_id FK
        datetime time
    }

    DerivedSignalCalibration {
        int id PK
        int derived_signal_id FK
        datetime time
        float yaw_offset
    }

Processing Pipeline¶

Raw configuration events (JSON arrays) are transformed into typed records by the processing subpackage:

1. Parse — DelimitedSignalKeyParser extracts signal name and property from keys like "NRT_WTG_TP_STRAIN/status".
2. Accumulate — ProcessedSignalRecord and ProcessedDerivedSignalRecord collect status, offset, CWL, and calibration rows.
3. Convert — SignalProcessingResult.to_legacy_data() produces the archive-compatible dict shape consumed by the upload layer.

Upload Workflow¶

The signal upload orchestrator (ShmSignalUploader) follows this sequence:

1. Create main signals — one per signal name, returns backend IDs.
2. Create signal histories — status rows per signal.
3. Create signal calibrations — offset/CWL rows per signal.
4. Create derived signals — one per derived signal name.
5. Create derived signal histories — with parent signal patches.
6. Create derived signal calibrations — calibration rows per derived signal.

See the Process Signal Configs how-to guide for a step-by-step recipe.