testo 862

The Gap It Fills

It’s worth understanding, because the 862 sits in a specific place in the range.

The testo 860i has no screen. It clips to a phone and the app becomes the display, which keeps it small, but means the phone has to be there, charged and allowed on site.

The testo 868 and above are handheld instruments with their own screens, built for producing survey reports, and priced to match.

The 862 is a camera with its own screen that fits in a pocket. There’s no phone required, it’s ready to use in seconds, and it’s small enough to carry daily, rather than fetch from the van when someone suspects a problem.

That last point matters more than any specification. A thermal camera left in the office finds nothing. One that lives in a pocket gets used on the job that wasn’t about thermography at all, which is where many faults are actually spotted.

Two Resolutions

Both have a 25 Hz refresh rate, thermal sensitivity under 50 mK and a minimum focus distance of 0.25 metres.

The difference is the detector, and it decides how small a target you can measure and from how far.

That’s worth putting a number on. The 862-1 has a geometric resolution of 4.62 milliradians, so one pixel covers about 4.6 millimetres at one metre, and 46 millimetres at ten. Since a reliable temperature needs the target to cover several pixels, the practical figure is roughly a 15 millimetre target at one metre, or 140 millimetres at ten.

The 862-2, at 3.75 milliradians, covers about 3.75 millimetres per pixel at one metre, so it needs roughly an 11 millimetre target at one metre, or 110 millimetres at ten. It also has a wider field of view, so it takes in more of the scene from the same spot.

So the 862 is a close range instrument by design. A terminal in a switchboard at arm’s length, a wall, a radiator or a pipe run are all well within it. A connection at height, or a panel on a roof seen from the ground, isn’t.

Why it matters is worth stating. A target smaller than the camera’s spot size gets averaged with its cooler surroundings, so it reads cooler than it actually is. Under resolving doesn’t give a blurry picture of a fault. It gives a fault that looks acceptable.

Fast Diagnostics on the Spot

The 862 is built for quick decisions during an inspection.

Built in alarms, automatic delta T, and hot and cold spot detection pick out what matters straight away. Up to five adjustable measuring spots and three regions of interest can be placed on an image. DeltaHeat quickly shows the spread between flow and return temperatures on heating systems.

Fusion mode blends the thermal and visual images, and picture in picture shows them together, so it’s easy to see exactly what was being looked at. The 2 MP visual camera focuses from 0.2 metres.

Mould and Electrical Checks

Humidity mode assesses mould risk. Readings from an optional testo 605i thermohygrometer transfer over Bluetooth straight to the camera, or the values can be entered by hand. A dedicated humidity palette shows the result.

Electrical mode works the same way with an optional testo 770-3 clamp meter. A hot connection at 20 amps and a hot connection at 200 amps are very different findings, and recording the load alongside the temperature makes the difference clear.

Two 862-2 kits package these up: the Electrical Kit includes the testo 770-3 clamp meter, and the Mould Kit includes the testo 605i thermohygrometer.

Built for Daily Carrying

The 862 weighs 215 grams, is rated IP54, and is drop tested to 1.5 metres. The built in battery runs for about 3 hours, and charges over USB-C, with a 15 minute charge giving 25 minutes of use.

Images are stored on 12 GB of internal storage, and can be analysed in testo IRSoft, which is free. The camera can also record non radiometric video.

Choosing Between the Two

The decision comes down to how close you can get, and how much you need to see.

The 862-1 suits close range work, where the target is reasonably large: a terminal at arm’s length, a radiator, a wall or a section of pipe.

The 862-2 gives 49,152 measuring points against 19,200, with a finer geometric resolution and a wider view. Smaller targets become workable, and it’s the version that comes in the Electrical and Mould Kits.

If the work is varied, or the reading has to be trusted rather than indicative, the 862-2 is worth having. Where it’s consistently close range on reasonably sized targets, the 862-1 does the job for less.

Where It’s Used

Electrical maintenance and fault finding. Switchboard and distribution board checks. Building fabric and insulation assessment. Damp, condensation and mould investigation. Underfloor heating tracing. Blocked pipe and radiator diagnosis. HVAC fault finding. Refrigeration and cool room checks. Plumbing leak location. General maintenance and service work. Property inspection and reporting.