Testo 405i Thermal Anemometer (Smart Probe)

Testo 405i Overview

The testo 405i is a hot-wire Smart Probe with a telescope that extends to 400 mm. It sends air speed, temperature and duct volume flow to the testo Smart App, where you set the duct size, take timed or multi-point averages and send the report as PDF or Excel.

Who the Testo 405i is for

The Testo 405i suits HVAC technicians and commissioning engineers who need air speed and duct volume flow without carrying a handheld meter, since the phone becomes the display. A hot-wire sensor reads low air speeds that a vane probe misses, which helps at supply grilles, in low-velocity ducts and when checking draughts.

Accuracy bands from the testo 405i data sheet (07.2023):

• ±(0.1 m/s + 5% of reading) from 0 to 2 m/s
• ±(0.3 m/s + 5% of reading) from 2 to 15 m/s
• ±(0.5 m/s + 5% of reading) from 15 to 30 m/s, with 0.01 m/s resolution
• Temperature -20 to +60 °C, ±0.5 °C, 0.1 °C resolution

Practical points from the testo Smart Probes manual:

• Switch the probe on above 10 °C with the protective cap closed so the hot wire can warm up at zero air speed
• An arrow on the housing shows the flow direction testo specifies for best results; line it up with the air stream
• Readings update once a second and can be shown in m/s, fpm, m³/h, cfm or l/s
• Bluetooth range is about 15 m in free field; testo currently specifies iOS 13 / Android 8 or newer and Bluetooth 4.2 for the Smart App

For higher, steadier air speeds at grilles the Testo 410i vane anemometer is the alternative, and the Testo 605i thermohygrometer pairs with the 405i for heating and cooling output. The Testo 510i covers differential pressure and Pitot readings. Compare other anemometers or browse the Testo brand page.

Testo 405i Key Features

Strong points of the Testo 405i:

• Bluetooth® thermal anemometer operated via the testo Smart App
• Measures air velocity (0 to 30 m/s), temperature and volume flow
• Telescopic 400 mm probe shaft for reaching into ducts
• Ideal for duct measurements and indoor air-velocity checks
• Calculates cooling and heating output with the testo 605i
• Compact 200 × 30 × 41 mm body on 3 AAA cells, rated by testo for about 15 hours of use

Testo 405i Applications

Where the Testo 405i earns its keep:

• Air velocity and volume flow measurement in ventilation ducts
• Indoor air-velocity checks and draught detection at windows
• HVAC commissioning, balancing and service
• Cooling/heating output calculation with a paired thermohygrometer

What comes with the Testo 405i (0560 1405)

Inside the Testo 405i pack:

• testo 405i thermal anemometer Smart Probe
• 3 x AAA micro batteries
• Calibration protocol

Testo 405i FAQ

Quick answers for Testo 405i buyers:

• How long do the batteries last in the Testo 405i? Testo rates it for about 15 hours on 3 AAA cells. For comparison, the 410i vane probe is rated for about 130 hours.
• Can it calculate duct volume flow? Yes. You enter the duct shape and size in the testo Smart App, and it calculates volume flow from the measured air speed, including timed and multi-point averages.
• Does it have a display? No. All readings, graphs and reports are on the phone or tablet. Reports can be sent as PDF or Excel files.
• What case fits it? Testo lists the Smart Case (VAC), 0516 0260, which holds the 405i together with the 410i, 510i, 605i, 805i and 905i.

Why buy the Testo 405i from MME

Not sure whether a hot-wire or a vane probe suits your ducts? Tell MME the duct sizes and the air speeds you expect, and we will point you to the testo 405i or the testo 410i and quote. Download the testo 405i datasheet (PDF)PDF