Testo 405i Bluetooth Thermal Anemometer Smart Probe – Measuring the Air Inside and Out
This thermal anemometer smart probe is the perfect tool for getting accurate readings on air velocity, temperature and volume flow. It's specifically designed for use in ventilation ducts and indoor environments where a vane anemometer might not be able to reach - behind grilles, through service hatches or in cramped HVAC spaces. The Testo 405i connects to your phone via Bluetooth and then you can use the free Testo Smart App to operate it remotely and start getting instant results. The app not only lets you set up and start measuring, it also does the maths and spits out a PDF or Excel document for you to save or email off.
The Testo 405i is especially useful for jobs where a vane anemometer won't cut it – it's a tiny hot wire sensor that reaches into tight spaces and gives you accurate air velocity readings from way back in the duct. And because it's just a probe and not a full-on device, it's a heck of a lot easier to use when the probe is stuck in a duct and you're trying to read the results on your phone – much more practical than trying to read a screen on the probe itself from across the room.
The Testo Smart App does all the hard work for you – just tell it the duct's dimensions and geometry and it'll calculate volume flow automatically throughout the whole measurement session. Plus, it does timed and multi-point mean calculations, which gives you a really solid idea of how much airflow is going on in the duct. Trend analysis and data visualisation makes it easy to spot any issues with airflow and to get that information down in writing. When you pair the 405i up with the Testo 605i thermohygrometer you even get cooling capacity and heating output calculations – really handy for getting a complete picture of how your HVAC system is performing.
Note the Testo 605i does need to be purchased separately if you want to do those extra calculations.
Key Features & Benefits
Hot Wire Accuracy – Measures air velocity from 0 all the way up to 30 m/s, and it's accurate right down to 0.01 m/s – perfect for slow airflow jobs where vane anemometers start to struggle.
Long Reach Telescope – 400mm of telescope lets the 405i reach into tight spaces, behind grilles and through service hatches – places that are impossible to get to with a regular vane anemometer.
Testo Smart App – Easy Volume Flow – Tell the app the duct's dimensions once and it'll do the maths for you, giving you volume flow calculations all session long.
Operate from Your Phone – Much easier to use when the probe is stuck in a duct than trying to crane your neck to see a screen on the probe itself.
Timed & Multi-Point Mean – Get accurate, repeatable measurements for commissioning reports.
Trend Analysis & Data Visualisation – Easy to spot airflow issues and get them down in writing.
PDF/Excel Reporting from Site – Email off your measurement logs directly from the app – no more scribbled notes or data entry.
Indoor Air Velocity & Window Draught Check – Detect draughts from leaky windows and get an idea of indoor air velocity - whole lot more useful than just duct measurement.
Pairs with Testo 605i for HVAC Diagnosis – Get a complete picture of how your HVAC system is performing when you pair it up with the 605i (sold separately).
Calibration Protocol Included – Ready to go straight out the box, and you get the calibration details in the package.
Ideal For
Measuring air velocity in ventilation ducts
HVAC commissioning and diagnostics
Measuring volume flow in rectangular and circular ducts
Indoor air velocity checks and draught detection
Window airtightness investigation
HVAC diagnosis and system performance assessment
Engineers working on building services and ventilation
Anybody who needs to measure airflow in tight spaces.
What's in the Box?
Testo 405i Thermal Anemometer Smart Probe
400mm long telescope
3 × AAA batteries
Calibration details
Why Buy the Testo 405i?
Hot Wire Can Go Where Vane Can't – This thing can measure in places the 100mm vane probe just can't get to. If your work involves measuring ducts beyond outlet grilles then a thermal anemometer like this is the one for you – not some sort of workaround.
Accuracy Down to 0.01 m/s – At low airflow rates vane anemometers start to lose their accuracy, but the hot wire sensor on the 405i resolves to 0.01 m/s and gets it spot on. Perfect for those low-velocity diagnostic jobs.
The Telescope Makes Duct Access Hassle-Free — We've all been there trying to fish a probe through a duct while squinting at a small display on the end - not the most fun task. With the 400mm telescope and your phone, all that's changed. Stick the probe in the duct and read the display on the screen in front of you, its a whole lot easier.
A Useful Addition to Your Kit, Not a Replacement — Let's be clear - the 405i is a duct measurement tool and the 417 kit handles grille and outlet measurement. So what's the point of having both? When you're doing a proper HVAC commissioning, having the right tool for the job really makes all the difference - especially when you need to get into tight spaces.
The Perfect Probe for Tactically Tough Jobs Testo 405i Bluetooth Thermal Anemometer Smart Probe is in stock and ready to go as soon as you order it. Get it today and you'll be able to take accurate airflow measurements in any spot on the site - even the ones a vane probe can't quite reach.
Specification
Testo 405i Bluetooth Thermal Anemometer Smart Probe Specification
Brand
Testo
Model
Testo 405i Smart Probe
Sensor Type
Hot wire thermal
Velocity Range
0 to 30 m/s
Velocity Accuracy
±1 digit ±(0.1 m/s + 5% of mv) (0–2 m/s); ±(0.3 m/s + 5% of mv) (2–15 m/s)
Testo 405i Bluetooth Thermal Anemometer Smart Probe Features
Hot Wire Thermal Sensor — Measures air velocity from 0 to 30 m/s — accurate at low velocities (0.01 m/s resolution) where a vane anemometer struggles.
400mm Extendable Telescope — Reaches into ventilation ducts, behind grilles and through service hatches — accesses measurement points that physical size makes impossible with other probe types.
Testo Smart App — Automatic Volume Flow Calculation — Input duct dimensions and geometry once; the app calculates volume flow automatically throughout the measurement session.
Remote Smartphone Operation — Phone is the display — read measurements from your hand while the probe is in the duct, no craning to see a display at the probe end.
Timed & Multi-Point Mean Calculation — Averaged readings across a duct cross-section — precise, repeatable results for commissioning documentation.
Trend Analysis & Data Curve Visualisation — Visual airflow data in the app — easier to identify issues and communicate findings to clients.
PDF & Excel Reporting from Site — Email measurement logs directly from the app — no manual logging, no data to process back at the office.
Indoor Air Velocity & Window Airtightness Check — Detects draughts from non-airtight windows and checks indoor air velocity distribution — wider diagnostic capability beyond duct measurement.
Pairs with Testo 605i for HVAC Calculations — Combined cooling capacity and heating output assessment when used alongside the Testo 605i thermohygrometer (sold separately).
Calibration Protocol Included — Ships ready for professional use on documented installations.
