Video: IRDL708

Video transcript

A 640 by 480 thermal camera that places every hot spot in its real surroundings. How it works, how to measure well with it, and where it is used. In a switch room, dozens of cubicles look the same. A thermal image shows that something is hot, but on its own it rarely says which terminal, in which cubicle. A report needs both answers, and so does the person sent to repair it. An uncooled microbolometer of 640 by 480 pixels, from 8 to 14 micrometres. Its thermal sensitivity is 200ths of a degree,

and each pixel resolves 0.65 milliradians. At the front, the infrared lens, and above it the 5 megapixel visible camera, between its two lights, and the laser pointer. The handle runs along the top, the viewfinder sits at the back, and the touchscreen folds out from the side. From the side: a key switches the laser on, and the shortcut keys next to it can be assigned to the functions you use most. The screen opens and turns to any angle,

and the viewfinder is there for bright sunlight. The answer to the problem is fusion. The camera lays the thermal image over the visible one, as a blend or as a picture in picture, and saves both linked together. The hot spot appears where it really is: on this breaker, on this terminal. Before trusting a number, set the emissivity: how much of its own heat a surface really radiates. Bare aluminium, about a 5th.

Oxidised aluminium, about half. Paint, almost everything. Get it wrong and the reading is wrong, however good the image. Low emissivity also means reflection: a shiny busbar can mirror a lamp, or your own body. If a hot spot moves when you move, it is a reflection. Enter the background temperature, distance, humidity and ambient temperature, and the camera corrects the rest. Then the load. A contact only heats when current flows through it,

and the heating rises with the square of the current. Inspect at the normal load of the installation, write the load down with each image, and do not compare a reading at night with one at the peak of the day. Here the warmest point is the centre phase of the right-hand breaker. Its neighbours, in the same breaker and under the same load, are the reference. The other breaker is warm too, but evenly. And the visible image around the thermal window shows which device it is. The difference against that reference sets the priority.

A small one is recorded and inspected again. A clear one goes into the repair plan. A large or growing one is dealt with straight away. Take the limits from your maintenance standard, and apply them the same way every time. On screen, up to 10 movable areas give the maximum, minimum and average, and up to 5 lines draw a temperature profile. Isotherms colour a band of temperatures,

and an alarm warns by voice or colour when a limit is passed. The standard range runs from minus 40 to 650 degrees. With the optional calibrations it reaches 1200 or 2000, for foundries, metallurgy and combustion. Accuracy is two degrees or two percent of the reading, whichever is greater. In practice: set the emissivity and the distance first. Frame the target with the fusion on, focus, and scan. When something stands out, measure it against its reference,

then capture, with a voice or text note. Images go to an SD card of 8 gigabytes, or up to 32. Infrared files keep 14 bits of measurement data, video is recorded as H₂ 6 4 or with the original radiometric data, and each image can carry 60 seconds of voice. It can also work as a live sensor. Through the network port, with its own IP address, it streams the original image data or an MPEG 4 stream in real time. There is a video output for a monitor, an audio output, and a 12 volt input.

In the field, it weighs 1.75 kilograms with the battery, runs for 3 hours, and is sealed to IP 54, from minus 15 to 50 degrees. The laser is class two: never into anyone's eyes. And never point the camera at the sun. In the Amperis range, the IRDL708 is the most sensitive of the 4, and the one that brings fusion and live streaming to a 640 pixel camera. Thermal imaging, from Amperis.