Fluke Ti25

From the minute you pickup the Fluke Ti25 you know that you are holding a quality Fluke instrument. Solid, firm, soft touch rubber with plenty of FLUKE yellow… all these things are immediately noticeable and the impression is lasting. At 1.2kg it is not the lightest “point and shoot” camera in it’s class, but the quality and robust feel does fill you with confidence. A positive audible chirp on start-up let’s you know that the camera is firing up just moments before the flash screen appears. The camera boots up surprisingly fast, although it takes a couple more seconds for the image to calibrate and stabilise before it is in a useful state. For a 160×120 detector, the image is surprisingly good, in fact unbelievably good. This might have something to do with the 3.6 inch 640×480 VGA LCD display. Obviously to get a native image from 160×120 up to 640×480 involves some kind of enhancement, and Fluke have done believably well. My immediate suspicion is whether it will look as good in a report or on the PC as it does on the camera, something I will need to wait to find out. The stated thermal sensitivity of 100mk also appears to be conservative. This is a very crisp image, that would by first impressions appear to be better the stated sensitivity.

How high will it go?

The Fluke Ti25 treats us to a nice broad temperature range of -20 to 350°C, and it is split across 2 ranges giving the primary range excellent thermal sensitivity. Unlike most brands, the ranges are not user selectable, but in fact automatic. I feel that this function actually requires some user training as many people I have met who use this unit, aren’t aware of how this works. From the behaviour of the unit, first range is -20 to 125°C. When looking at a target above 125°C the heat seeking cursor will indicate >125°C. In fact it will show this result for an inordinate amount of time before deciding to automatically shift to the next range, which is indicated by the unit displaying the “calibrating” indicator on screen. The confusing part about this is that the unit periodically calibrates under normal operation and it is not clear that this calibration is associated with a change in the temperature range. At this point most novice or impatient users will simply move on, assuming the camera is doing it’s normal calibration, unaware that the camera is seeking the next measurement range and would have possibly given them a higher measurement reading. Sounds confusing… it is. Also when you are continuously working on higher temperature targets utilising range 2, and you momentarily come across lower temperature targets the camera will automatically slip back to range 1. Each time it changes range it calibrates which involves several seconds of interruption. If you are never measuring over 125°C you won’t have a problem, but if you have to work in the >125°C range you will need to contend with this issue. Personally I find the automatic measurement range selection very frustrating.

How good is the measurement?

With a 23° FOV lens, the spatial resolution on this unit is a very usable 2.5 mrad. While the manufacturer does not quote a distance to spot ratio (or MFOV), my laboratory tests have it at approx 100:1. That means it can measure a 10mm target at 1 meter and therefore uses approx 4×4 pixels to obtain a measurement. For this resolution size, it is consistent with industry standards. Disappointingly no optional lenses are available with the Fluke Ti25. I am surmising, but the attitude at the time of this units inception was wide angle and telephoto lenses belonged in the realm of professional thermographers using much higher resolution equipment. They were also horrendously expensive, likely ruling them out as a viable accessory. Nowadays, optional lenses have become very affordable and useful accessory.

How good is that screen?

The Fluke Ti25 screen is nothing short of fantastic. I’ve already mentioned the 640×480 display, however it’s the brightness and vibrancy that makes it so easy to see under a variety of conditions. The 3.6 inch screen has a gentle forward slope that makes it ergonomically easy, and the plastic screen cover offers surprisingly good performance in outdoor sunlight. No external screen performs great in sunlight (when compared to a internal viewfinder), but this is still readable and provides a good amount of glare resistance. If you intend to use the Fluke Ti25 for extended periods in bright sunlight I cannot recommend highly enough the optional sunshield, which is a high quality accessory.

Please tell me it has FUSION?

Yes it does, and FLUKE sold the FUSION concept very well as a “must have function” with models like the Fluke Ti25. What is FUSION you ask? It is the blending and/or overlay of the thermal image with the visual daylight image. While in some contexts fusion can be a very dramatic presentation tool, my personal view is that it is often misused and undermines the credibility of information presented in the thermal report. Too often, critical evidence of material condition, emmitance or reflectance properties are obscured and unobtainable with the overlay or blending hiding essential information. Particularly for electrical and mechanical inspections I insist on obtaining a clear and unobstructed visual and thermal image to assess the target conditions (and results) for myself. On a side note, the visual is a respectable 640×480 image that aligns very well with the thermal image. Thumbs up!

Is it easy to use?

When it comes to ease-of-use, the Fluke Ti25 is quite polarising. On one hand, first time users and novices will find it a breeze, and the user interface hits its mark with this audience. However, with either formal training or a little experience, I feel a user will quickly reach it’s limitations. The user interface on the Fluke Ti25 is very straight forward and exceptionally easy to use for the first time or novice user. The character size is good for those more visually challenged and the menu titles are very easy to read. The battery indicator is a permanent feature in the top right, and is surprisingly accurate. Date and time are presented onscreen, but alas no Emissivity value which can be frustrating when the person before you thinks they know something about emissivity and have adjusted all the settings! I really like that the unit has a centre point measurement tool as well as hot/cold seeking cursors which generally provide the most important temperature references for the scene. Three buttons below the screen and the front trigger provide all the control to the menu system. The buttons are large and well spaced, and easily operated with gloves or protective clothing. This is a sequential menu system, whereby you scroll through each and every page of the menu by hitting the centre menu button. Each of the 3 buttons corresponds to an onscreen command or value. With only 2 functions available on each page, I counted 6 pages of menus from start to finish. At this point in the operation, more advanced users will become very frustrated with the step through menu. Each menu screen or page must be sequentially clicked through to obtain the following page, meaning that if you need to access a function like ranging or emissivity adjustment you will need several clicks to find it in the menu, and several more clicks to adjust it’s setting. This get’s very cumbersome and tiresome. Moreover, the camera and processor can be a little slow to respond, with a definite “lag” in the user interface. Trying to use the instrument quickly results in “over clicking” or going past your menu choice due to impatience and waiting for the camera to catch up. To generalise, I would say the user interface discourages you from using more manually controlled settings and forces you to rely on the cameras “auto” modes to obtain the correct image settings. This won’t phase the “point and shoot” thermogapher, however an experienced user will get quickly tired of it. Trying to use the 3 button user interface to manually control the level and span settings is a frightful experience and one that most users will avoid. The downside to this is that as any professional will tell you, you can be much more time efficient on an inspection utilising a user controlled level and span. Beyond the user interface, the Ti25 has great ergonomics and control. The camera is well balanced and has a large sturdy hand grip with one of the best adjustable hand straps in the business. It provides a firm grasp around your hand to minimise accidental drops, and can be easily adjusted for left of right handed use. Also, if your hand and/or index finger are sufficiently long you can also reach the focusing lens for single handed operation. Smaller hands/fingers will be challenged by the function, however for me it works perfectly. The camera is tremendously easy to get a sharp clean focus. For me, one of the biggest let downs of the Fluke Ti25 is the image save process. With any type of plant or professional inspection I am reliant on a detailed “running sheet” to document the inspection (ie asset, asset ID, location, load and other relevant conditions). An important aspect of this running sheet is being able to document the thermal image number next to the asset identification. Sadly, upon squeezing the trigger on the Fluke Ti25 and pressing the store button the only onscreen information I get is that the image is “storing” and then “image stored” before returning to a live image. There is no announcement of an image number at all, which is a common feature on most cameras. As such i cannot easily document the image capture against my running sheet, and need to go back into the menu system and recall from memory and image to indentify it’s number. This is a time consuming and painful exercise. Hopefully this is something Fluke will address with future firmware upgrades.

But i can record voice, right?

Some may argue that the voice annotation may negate the need for “image numbers”, however in 15 years of performing thermographic surveys I have never found a more reliable method of documenting a survey than using a detailed (hand written or electronic) running sheet. Additionally in most industrial environments, voice annotations and recordings are absolutely useless due to high levels of ambient noise. For those interested, you can find an example of my running sheets here…

But it’s a Fluke…

There is no doubt the Fluke Ti25 is built to the high Fluke standards of quality we’ve come to expect from this brand. This name is synonymous with high quality electrical test equipment and this unit is top of it’s class for finish and fitment. The 2 meter drop proof specification inspires confidence in even the clumsiest of users. Keeping in mind that the Fluke Ti25 is pitched at plant maintenance personnel it does not have a field replaceable battery. The completely sealed unit, utilises and internal battery that gives between 3-4 hours of field use. This of course would be a significant limitation for the professional user and they would need to seek a model like the Fluke Ti32 that has field swappable batteries. However for in-house personnel, where a power socket is never far and anything more than a 4 hour sojourn into the plant is unlikely this is unlikely to prove inconvenient. It also simplifies the practice of battery management, where so often in large organisations batteries get misplaced or lost by the various users who share the asset.

Yeah… but what about the software?

The Fluke Ti25 is bundled with free software called SmartView, and let me say from the outset I am very fond of this software. The package I have been using is version 3.1, which has a much needed feature of template customisation that was absent from earlier versions. I will admit that the template customisation is not easy, and it’s taken me more than a few hours (or days) to master XML based templates (In Word), but it can be done and the result is very professional. For those familiar with any of my reviews, you will know I am biased toward Microsoft Word based reporting writing software, and this is no exception. Most of us have spent years self teaching and fumbling our way through this Microsoft behemoth and have now become quite proficient. A well tailored Word document can return some incredibly professional results. The mechanics of this software are very simple and straight forward and easy for anyone to master. For those who know their way around, it is also surprisingly fast. This is one package I would say suits novice and professionals alike. When it comes to value for money, it’s not an easy task to assess the Fluke Ti25 or any Fluke product for that matter. These cameras are not cheap, and are at the pointy end of the scale in most comparisons. Much of the value comes with the brand; which for me is the perception of uncompromised quality, and the peace of mind of trouble free ownership. That said, for the price of a Ti25 at this time of writing a high resolution camera with 4 times the resolution could be had for the same money.


Imaging performance
Field of view 23° x 17°
Spatial resolution (IFOV) 2.5 mRad
Minimum focus distance
  • Thermal lens: 15 cm (6 in)
  • Visible (visual) light lens: 46 cm (18 in)
Focus Manual
Image frequency 9 Hz refresh rate
Detector type 160 X 120 focal plane array, uncooled microbolometer
Infrared lens type 20 mm F = 0.8 lens
Thermal sensitivity (NETD)  0.09 °C at 30 °C target temp. (90 mK)
Infrared spectral band 7.5 ?m to 14 ?m
Visual camera 640 x 480 resolution