Testo 405i Hot-Wire Anemometer

The Testo 405i is a thermal (hot-wire) anemometer in the Testo Smart Probes family. It measures air velocity and air temperature in ducts and at outlets, and calculates volume flow from the duct dimensions and shape entered on the phone. The probe has no display of its own. Readings go over Bluetooth to measureQuick or the testo Smart App, and the telescoping shaft extends to 15.7 in (400 mm) to reach the center of a duct through a test port.

Air Velocity and Temperature Measurement

The hot-wire sensor covers 0 to 5,906 fpm (0 to 30 m/s) at 2 fpm (0.01 m/s) resolution. Accuracy is ±(20 fpm + 5% of reading) up to 394 fpm (2 m/s), ±(59 fpm + 5% of reading) from 394 to 2,953 fpm (2 to 15 m/s), and ±(98 fpm + 5% of reading) from 2,953 to 5,906 fpm (15 to 30 m/s). An NTC sensor reads air temperature from -4 to 140 °F (-20 to 60 °C) at ±0.9 °F (±0.5 °C). Timed and multi-point averaging supports a duct traverse, and Testo pairs the 405i with the 605i thermohygrometer for heating and cooling capacity measurements.

measureQuick Wireless Integration

The 405i connects to measureQuick over Bluetooth alongside the other Testo Smart Probes on the job. Air velocity, air temperature, and calculated volume flow land in the test record with no hand transcription, recorded with the static pressure from a 510i and the temperature and humidity from 605i probes. That puts a measured airflow number on the job to check against the 350 to 450 CFM per ton range most systems are designed around.

Build and Field Readiness

The 405i measures 7.9 x 1.2 x 1.6 in (200 x 30 x 41 mm) and fits the Testo Smart Case with the 410i, 510i, and 605i. Three AAA batteries give about 15 hours of run time, so a full day of traverses calls for spares. It operates from -4 to 122 °F (-20 to 50 °C) and ships with batteries and a calibration protocol.