[Vineyard & Winery Elf EN](https://help.vineyardelf.com/index.md) / [VineyardElf](https://help.vineyardelf.com/vineyardelf.md)

# [Leaf Wetness Sensor (LWS Sensor)](https://help.vineyardelf.com/leaf-wetness-sensor-lws-sensor.md)

## What is the LWS Sensor?

The LWS (Leaf Wetness Sensor) measures the surface wetness of grapevine leaves. Accurate leaf wetness data is key to precisely forecasting the risk of fungal infections, especially downy mildew.

## Why does it matter?

**The 50 degree-hours rule (h°C)**

A downy mildew infection requires:
- A wet leaf for a certain period of time
- A suitable temperature

Formula: `temperature (°C) × wetness duration (h) ≥ 50 h°C`

Example: A leaf wet for 5 hours at 12°C = 60 h°C = **infection risk!**

## How it works in VineyardElf

### Without a physical sensor (Proxy model)

If you don't have an LWS sensor, the system estimates leaf wetness based on:
- Air humidity > 85%
- Rainfall > 0

**Accuracy:** ±30% (estimate)

### With an LWS sensor

The physical sensor measures the actual surface wetness of the leaf.

**Accuracy:** ±5% (precise data)

## What you see on the dashboard

The "Leaf Wetness" card shows:

- **Degree-hours (48h)** - the main risk metric
- **Wet (24h)** - how many hours the leaf was wet
- **Now** - current wetness
- **Status**: Dry / Wet / ⚠️ Infection risk

Threshold colors:
- 🟢 Green (0-70%) - safe
- 🟡 Yellow (70-100%) - caution
- 🔴 Red (>100%) - infection risk!

## Sensor technical specification

Recommended hardware:

| Component | Description |
|-----------|-------------|
| LoRa E5 Mini | Communication module (STM32 + LoRa) |
| SHT40 | Temperature and humidity sensor |
| LWS PCB | Capacitive leaf wetness sensor |
| IP67 enclosure | Waterproof protection |

**Battery life:** 2-3 years on AA batteries

**Measurement interval:** every 5 minutes

## Integration with disease models

LWS data is automatically used by:
- Downy Mildew model
- Powdery Mildew model
- Crop protection alerts

## Feature status

- ✅ Data model in the system
- ✅ Monitoring card on the dashboard
- ✅ API for receiving sensor data
- 🚧 Hardware in prototyping phase