The testo 425 is a compact yet highly capable hot wire anemometer, purpose-built for accurate flow velocity, volume flow, and air temperature measurements within ventilation ducts. Whether you’re performing system commissioning, troubleshooting, or airflow balancing, the testo 425 provides reliable data quickly and effortlessly.

At the heart of its performance is a cable-connected telescopic hot wire probe that extends up to 820 mm, allowing easy access to hard-to-reach or overhead ducts. The instrument is optimised for use in HVAC and ventilation systems, where precise readings and efficient data handling are essential.

With built-in automatic calculations, the device can generate time and multi-point averages and compute volume flow directly, saving time and eliminating manual errors. For even greater efficiency, the testo Smart App allows users to configure measurements, view real-time data on a smartphone (as a second screen), and manage results with graph visualisation, memory storage, and fast report generation.

Rugged, lightweight, and user-friendly, the testo 425 is the ideal choice for professionals looking for a smart, dependable solution to ventilation flow diagnostics.