Thermal cameras can spot problems you can't see - what I've learned after years of testing

Follow ZDNET: Add us as a preferred source on Google.ZDNET's key takeawaysThermal cameras don't have to cost thousands (but they can).Thermal cameras come in standalone versions, built into smartphones, and dongles.They literally give you a money-saving superpower.I like tools. One of my earliest memories is using plastic tools with my grandpa, and I've had a toolbox filled with tools since my early teens. Over time, many of the hand tools have given way to power tools; in recent years, I've added a few more exotic tools to the kit -- things like a and (yes, I like lasers, too). But one of the most useful "modern" tools in my toolkit these days is a thermal camera. This tool has, without doubt, saved me thousands of dollars over the years. When most people think of thermal cameras, two things typically come to mind -- the 1987 hit movie starring Arnold Schwarzenegger, or military optics. Most are surprised to learn that not only can you buy yourself a thermal camera, but they can cost . Also: I bought a thermal camera for my Android and it spotted a hidden hazard right awayTypes of thermal camerasBefore I get into why thermal cameras are a vital tool, let me take you through the various options on the market. You'll find that there are three types of thermal cameras you can buy:1. Standalone thermal camerasThese are handheld units with a single purpose -- the one-trick pony of the thermal camera world. They range from high-end professional units like the , , and the (you should probably be sitting down when you check out the prices of these), to more sanely priced cameras aimed at the household fixer, like the , , or the . There are pros and cons to standalone devices. The biggest con is that it's one tool for one job, and if you don't need a thermal camera often, it's going to spend a fair bit of time in a toolbox. The upside: They are robust, dedicated bits of kit that offer great accuracy and are relatively easy to use -- switch them on, and point them at whatever you want to measure thermally.2. Thermal camera donglesThese are small thermal cameras that attach to smartphones (and sometimes computers) and are controlled using an app. There are a lot of positives to this -- they're small and can be used at the end of a cable (so they can get into tight places), there's no battery to keep charged, and -- because they're tied to a smartphone -- getting images and video off them is easy. But there are some cons. First, they're not cheap (you can buy cheaper, but not necessarily better) standalone units. They're also small, so they're easy to lose in a toolbox or on a job site. Also, because they rely on a smartphone, it can limit you to a specific platform, although a few models will work on both Android and iPhone.Also: I invested in a thermal imaging camera for my iPhone and Android - it's already paying offI've tested a lot of these, and they're a great compromise between a standalone system and a device with a built-in thermal camera. Some of my favorites are the (iOS and Android), (iOS and Android), and the (iOS and Android).3. Smartphones equipped with thermal camerasBelieve it or not, there are a number of Android smartphones on the market from companies such as Blackview, Ulefone, and Oukitel that have built-in thermal cameras. Most of the time, these smartphones are also ruggedized, making them perfect for use in workshops or out in the field. I've tested many of these thermal camera-enabled smartphones, and a few of my favorites are , , and the .Also: I checked my GFCI breaker with a $220 thermal camera - and it proved me wrong (in the best way)The most obvious pro of a unit like this is that since we're pretty much attached to our phones, you're within arm's reach of your thermal camera. And since we regularly charge our smartphone, the thermal camera will also be charged.The biggest downsides are that you won't find thermal cameras in any flagship smartphones, you won't find an iPhone kitted out with one, and since most cameras are ruggedized, they can be on the bulky side. Why are thermal cameras so useful?Thermal cameras give you the superpower of being able to see things that are otherwise invisible to the human eye. And because of the sensitivity of even cheap thermal cameras, they're good at spotting small differences in temperature on things that are both big and small. Even a can detect the differences in air temperature in your nostrils when you breathe in versus when you breathe out, and can detect the residual temperature after you've touched something with your finger. That's a fair degree -- no pun intended -- of sensitivity, and this is enough to let you do some pretty cool things. Here are a few tasks that I've accomplished with my thermal cameras over the past few months:Also: This USB-C accessory unlocked thermal imaging powers on my Android and iPhoneEnergy audit: This is where you use the camera to look for heat loss around windows and doors, and for spots in roofs and walls where insulation is thin or missing, which can let heat escape. Electrical fault finding: Overloaded circuits, dodgy breakers, and loose electrical connections will show up as hot spots, giving you a heads up that something might be wrong well in advance of things becoming a fire hazard. Damp inspection: Moisture making its way into the loft or ceiling will show up as a cool patch, so checking these areas after rain is a good way to spot trouble before mold and rot take hold.Leaky plumbing: Wet patches behind walls or under floors hold heat differently than dry material, so otherwise hidden leaks will show up without having to take a sledgehammer to your home.Finding pests: Think you have mice, rats, or a wasp's nest in a loft or wall cavity? Animals give off enough heat to show up on a thermal image, even through a wall. Yes, they'll show up! Spotting faulty components on circuit boards: Faulty things have a tendency of either overheating and showing up like hotspots, or being completely dead and showing up as a cold spot. The best way to learn your new superpower The best way to learn how to use a thermal camera is to use it. Yes, I know, it sounds simplistic, right? But it works. Keep the camera with you and point it at everything. Yeah, you'll look weird (less weird if your thermal camera is built into a smartphone), but it'll give you a good idea of what the world is supposed to look like in the thermal range of the spectrum. You'll notice all sorts of strange and interesting things just by doing this. Then, once you come across things that are overly hot or cold, they'll stand out to you. Need some more inspiration? Here are a couple of videos that will help. The other day, there was an issue with a water heating tank. It suddenly became intermittent, sometimes heating the water, sometimes not. This was a repeat of a similar problem that happened while I was away from home a few weeks ago. That time, someone else had to be brought in. The result was about $1,500 spent on diagnosing the problem and buying and fitting the parts supposedly required to fix it. I didn't mind the cost except... ... it didn't fix the problem. Also: Should you buy a $40 earwax camera? I did, and keep finding new ways to use itThis time, I grabbed my thermal camera, followed the wiring from the switch to the heater, and found a bad connection in a wall switch. The giveaway: There was more heat from the metal box than I would have expected. It turned out that one wire had come loose. I refitted the wires, and it was finally fixed (hopefully for good). The thermal camera saved the day, again.