Compact in-line UV absorption sensor for real-time total chlorine measurement

Overview

This solution is a compact, in-line sensor designed for real-time measurement of total chlorine in water. It addresses the need for continuous monitoring of chlorine levels in space-limited and field-deployable environments where traditional laboratory-based instruments are impractical. By leveraging ultraviolet (UV) absorption spectroscopy with UV light-emitting diodes (LEDs) and a highly sensitive silicon photomultiplier (SiPM), the sensor delivers accurate chlorine detection below 0.1 mg/L in a small footprint suitable for integration into existing water management and treatment systems.

Technical specifications

• Measurement principle: UV absorption spectroscopy targeting the absorption bands of mono-, di-, and tri-chloramine species, which exhibit peak absorption wavelengths between approximately 260 nm and 340 nm
• Light source: Commercially available UV LEDs with peak wavelengths ranging from 255 nm to 410 nm, covering the full absorption spectra of total chlorine
• Photodetector: Silicon photomultiplier (SiPM) based on avalanche photodiode technology, capable of single-photon response with ultrahigh gain to overcome the inherently low absorption of chlorine
• Optical components: Integrated optical filters for wavelength selection and noise reduction
• Electronics: Microprocessor-controlled circuitry with precise LED current control, temperature feedback, current sensing, and data transmission capabilities
• Stability features: Pulsed LED emission and precise driving current control to compensate for junction temperature effects and ambient condition variations
• Form factor: Integrated unit smaller than 10 cubic centimeters, designed for in-line installation at required flow rates

Technology readiness level

The sensor is at an early-to-mid stage of development. The research team brings validated expertise in LED-based optical and fluorescent sensing platforms for handheld and field-deployable applications, including LED driving circuits, calibration to ambient conditions such as temperature, and handling of highly sensitive photodetectors. Future validation will focus on integrating the UV LEDs, SiPM, optical filters, and electronic components into a compact unit under 10 cm³ and testing performance at the required flow conditions to confirm reliable measurement of total chlorine below 0.1 mg/L in an in-line configuration.