Brenton WardJune 6, 2018 at 11:55 pm #289
The Testo 875 represents the entry level unit in Testo’s range of Building Thermography Cameras.* While these units are purpose built for building thermography, they actually perform remarkably well across a whole range of thermography disciplines. *With a temperature range up to 280°C the Testo 875 is plenty capable for the majority of electrical and mechanical applications.* A key design feature throughout the entire Testo fleet is the -20 to 100°C primary range which keeps the thermal sensitivity sharpest for building thermography.
For an entry level camera, the 875-1 has a surprising level of equipment for the modest price tag of (see pricing) at the time of writing. In reviewing entry level units I am always mindful that you only get what you pay for, therefore my evaluation is intentionally measured against price.* In this case you get a lot for a little.
Starting with a 160×120 detector measuring 19,200 pixels.* That’s right, not a 120×120 or anything less that you could expect to find in a camera of this price.* How does 80mk sensitivity sound?* Yep, that’s right, around 20% more thermal sensitivity than it’s competitors, and it’s not a mere exaggeration of spec, the image is clear and clean as you would expect from a camera boasting this sensitivity. Are you sure the price is correct?
I asked Testo the exact same question, and they have slashed prices across the entire range in an obvious effort to buy market share. And it seems to be working because I am told these things are selling like hotcakes.
If you asked me what really stands out about the Testo 875 I would be quick to say it was the 32° wide angle lens.* When you compare this to the more common 23°and 24° FOV lenses found on competitive models, the Testo 875 offers nearly 30% more view. *This is very important when working at close quarters in domestic structures.* Narrower angle lenses struggle to provide the desired perspective or imagery.*** This angle works nicely. I am acutely aware that with a 160×120 resolution you would not want to go any wider, however the unit maintains a respectable geometric resolution of 3.3 mrad.
It’s also very handy when working in close proximity to large motors and machinery.
I am impressed that Testo also include the MFOV (measurement field of view) or the Spot Size of the camera in their specifications.* This reveals that the camera is capable of measuring a 10mm target size at a distance of 1 meter.* That equates to a very respectable DTS (distance to spot size) of 100:1, which puts it on par with many other cameras with that use much narrower lenses to support this.
“How can this be?” you ask “wouldn’t a wide anger lens diminish the measurement capability?”
Usually it would, however it seems Testo have compensated for this by using fewer pixels for their MFOV to maintain quantitative measurement.* As such you get the best of both worlds; wide angle view for maximum scene capture and accurate temperature measurement.
With these 3 specifications in mind (resolution, thermal sensitivity and FOV) it’s easy to see why these units are favoured by building thermographers.* *This application places it’s highest demands on resolution and thermal sensitivity.* The wide angle lens is just the icing on the cake.
Testo Visual, 875 & 882 Comparison
FLIR i3, i5 & i7 Comparison
Testo Visual, 875 & 882 Comparison
FLIR i3, i5 & i7 Comparison
If you are after a visual image you will need to go up a model to the Testo 875-2, which combines the digital image capture with the thermal.* If you are using the Testo 875-1 and using a separate digital camera the software allows for easy attachment of your visual to the thermal so you can automatically generate a report with both.
The screen is nice. It’s a respectable 3.5 inch LCD that displays 320×240 screen resolution.* The angle is really good and allows the screen to be easily read under most conditions.* The brightness is great and really illuminates even the smallest objects clearly and precisely.* The camera does have brightness control, for those who might want to save some battery power.
Saving and image
The save function is good, actually it’s better than good, it’s excellent. Saving is as simple as clicking the trigger.* It’s the next bit where the camera excels, and that is it gives you the opportunity to choose and name a folder to save your images, enabling you to easily sort and organise yourself in the field. While many cameras offer a similar function, this is done with great simplicity via the large icon user interface. It is literally child’s play. Before we get carried away with bells and whistles, let us not forget the most important aspect of saving… Displaying an IMAGE NUMBER.* Following the save confirmation a large Image Number is displayed onscreen (for several seconds), allowing you to transcribe this all important number to your running report/sheet/notes so that you can later identify which image you assigned to what asset.* In my opinion this is the deal breaker in any camera.
What kind of batteries does it use?
The Testo 875 utilises a lithium ion battery that slides up through the base grip of the camera handle. It provides a very commendable 4 hours of operation.* The battery is very well designed and has moulded keyways (slots) into the side of the battery to prevent it from slipping all the way out on release.* This stops it from dropping to the floor (or on your foot) when you hit the battery release button.* You need to give it a firm pull to release it from the camera. It is a little disappointing that the standard model only comes with one battery and this must be charged within the camera with the provided mains adapter. At this price point it is hard to complain, and additional batteries and dual bay chargers can be purchased for a modest fee.
Toy or Tool?
The overall build quality of this unit is excellent. Plastic mouldings are well finished (no sharp edges) and the casing fits together well without gaps or overlaps.* Soft touches are added all over the unit with rubber panels and inserts on all the main wear and contact points.* The buttons feel firm and have a positive sound and feel when pressed. They are made of firm rubber giving a quality feel. There is nothing worse than cheap hard plastic buttons that click loudly making you feel like you are playing with a kids toy.* Definitely tool!
What’s it like to hold?
The Testo 875 quite simply has excellent ergonomics. The pistol grip is highly contoured to fit your hand with a confident and natural grip feel.* The buttons are within easy reach of my thumb, but it may challenge those with smaller hands. The unit is well balanced and weighted, unlike similar “pistol” style cameras that tend to be top heavy and require the user to really hold them in position.* The manual focusing lens turns effortlessly to provide crisp clean images, the rubberised lens ring providing ample feel and feedback to the fingertips.
Can you get any bits for it?
There is a long list of accessories and options for the Testo 875, including, telephoto lens, high temperature filter, sun shield, soft carry case, dual bay fast charger and IR lens protection filter,.
The sunshield accessory is pretty basic in terms of reducing sun glare, and offers more physical protection from bumps and knocks than it does sun.* I would recommend it on this point alone. However if you want real sun protection you would need to consider the “soft case” which provides excellent physical protection, a connection point for a lanyard and a broader visor for sun protection.* It is less of a case that a giant rubber boot that you can operate the camera in.
What’s the software like?
Testo provide their full Professional Reporting software at no extra charge.** At the time of this writing I tested Version 2.7 of the unoriginally titled ” IRSoft Software”.* While the name doesn’t standout, the software does.* This software is stable, bug free and put together very well. It would classify it as ideal for entry level users wanting to create, precise reports at the touch of a button.** What makes it entry level is that the recipe is simple, straight forward and hard to make a mistake. If trying to create something more detailed and elaborate it may disappoint seasoned professionals. I am a firm believer that when it comes to software you can’t be everything to everyone.* The end result is a very professional looking report with minimal fuss… which is what we all want, right?
In more detail?
My first impression is that it is neat and orderly, allowing one to work through their images with minimal distraction of confusion.* All the essential tools are located in the same “box” as the visual or thermal, so you don’t need to look far to find what you need.** One of the primary adjustment functions, the level and span, or in this case titled “temperature scale” is a large and impossible to miss function on the right side of screen. It utilises arrow sliders that get the job done with ease and give a good graphical representation of the image’s scale relative to the available temperatures measured.* It deals with isotherms and “colour saturation” functions (seen as “limit values”) in a very intuitive manner. Big thumbs up for this interface.
It does take a while to work out what all the little icons do, but at least when you roll over the icon with the mouse pointer you get ample indication of it’s function.
One nicety is that you can tweak the image brightness on the visual image, something that few manufacturers pay attention to.
Can you Zoom in on that buddy?
The answer to that is, “no sorry I can’t”. Something I was unable to find was a zoom control or function for the thermal image. Often, especially when imaging small targets like SMC’s on PCB’s I would like to zoom in to inspect the individual component.* I am not sure if I was missing something but could not find this function in Version 2.7.
An easy to use and straight forward report wizard allows you to choose from multiple templates and steps you through the reporting process. The software provides you with 5 industry standard templates pre-prepared.** This is quite common place in modern software, I would accept nothing less. Report templates can be customised and modified using a template editor and this is where things get a little difficult for those who want high levels of customisation and aren’t IT wizards themselves.* While you can add a personal touch with relative ease, creating more complex presentations is not as intuitive or easy as some word based templates utilised by other software.* It requires some work, but most people will end up with a satisfactory result.* Also, another minor criticism is that your final report is in a proprietary format (*.tir), however the software does enable you to save/export as a PDF.* There is no word option available.
Overall, it is what i would describe as robust and comprehensive software for general predictive maintenance or building diagnostic purposes.
At this time of writing I could not suggest a single unit available that could beat the Testo 875’s value for money.
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