> ## Documentation Index
> Fetch the complete documentation index at: https://docs.appliedaifoundation.org/llms.txt
> Use this file to discover all available pages before exploring further.

# UV Disinfection Technology

> How UV intensity is generated, measured, and why lamp efficiency degrades over time.

## The physics of UV-C disinfection

UV-C light (wavelengths 200–280 nm) causes **thymine-thymine dimers** to form in microbial DNA. This photochemical damage prevents cells from replicating, rendering organisms non-viable — even if they are not immediately destroyed.

Disinfection efficacy is **dose-dependent**:

```
UV Dose (mJ/cm²) = Intensity (W/m²) × Exposure Time (s) × 0.1
```

At a fixed flow rate and reactor length, increasing lamp intensity directly increases the delivered dose. This is why UV intensity is the primary compliance metric.

## How intensity is measured

Two intensity values appear in telemetry:

| Field                      | Description                                                                  |
| -------------------------- | ---------------------------------------------------------------------------- |
| `UVR_INTENSITY`            | Raw UV sensor reading in W/m²                                                |
| `UVR_INTENSITY_NORMALIZED` | Corrected for water temperature and transmittance via `WATER_QUALITY_FACTOR` |

Compliance checks in the dashboard use `UVR_INTENSITY`. The normalised value is available for analysis in the Data Export tab.

## Power output and compensation

As lamps age, they produce less UV output per watt of electrical power consumed. The system's Lamp Drive Controller (LDC) compensates by increasing power to maintain the intensity setpoint:

| Field                    | Description                                                        |
| ------------------------ | ------------------------------------------------------------------ |
| `UVR_POWER_OUTPUT`       | Current power delivered to the lamp array (% of rated capacity)    |
| `UVR_POWER_SETPOINT`     | Target power level commanded by the controller                     |
| `POWER_COMPENSATION_PCT` | Extra power percentage consumed to compensate for lamp degradation |
| `DEGRADATION_IMPACT_PCT` | UV output reduction (%) attributable to lamp aging                 |

A `POWER_COMPENSATION_PCT` of 20 means the system is consuming 20% more electrical power than new lamps would require to achieve the same UV intensity. This is a reliable early indicator of lamp aging before efficiency drops below warning thresholds.

## Lamp efficiency degradation curve

UV lamps degrade non-linearly over their operating life:

* **0 – \~1,500 hours**: Efficiency stays above 90%, minor power compensation needed
* **1,500 – 2,500 hours**: Gradual degradation, efficiency enters the 70–90% warning band
* **2,500 – 3,000 hours**: Accelerated degradation, replacement recommended before the 3,000-hour rated life

The Trend Analysis tab's **Lamp Efficiency & Power vs Runtime** chart visualises this degradation curve for any selected lamp, using data grouped into 10-hour runtime buckets.

## Water quality effects

Water conditions affect how efficiently UV light penetrates the flow:

| Field                  | Effect                                                  |
| ---------------------- | ------------------------------------------------------- |
| `UVR_WATER_TEMP`       | Cold water increases UV transmittance (less absorption) |
| `WATER_QUALITY`        | Turbidity descriptor                                    |
| `WATER_QUALITY_FACTOR` | Numeric multiplier used to compute normalised intensity |

Turbid or warm water requires higher lamp output to deliver the same effective dose. The LDC controller adjusts `UVR_POWER_SETPOINT` in response.

## The LDC (Lamp Drive Controller)

The LDC converts AC power to the high-frequency power needed by UV lamps and controls power delivery. Its health is critical because overheating shortens lamp life.

| Field             | Description                      |
| ----------------- | -------------------------------- |
| `LDC_AIR_TEMP`    | Compartment air temperature (°C) |
| `LDC_FAN_SPEED`   | Cooling fan speed (RPM)          |
| `LDC_FAN_STATUS`  | Fan operational state            |
| `LDC_WATER_ALARM` | Water ingress alarm flag         |

The `thermal_health` component of the system health score reflects LDC temperature management. See [Health Score Calculation](/methodology/health-score).