Infra-red thermometer

[BobtheBrewer]

I hope this is the right place for this topic. I am thinking of buying an infra-red thermometer with an accuracy of +/- 1%. Am looking for advice from anybody who uses one as to usability, type or value for money.


OK I have found my answers by searching, which I should have done before posting. Some savings for my pocket.

 

[TheWiggman]

I don't use one for brewing but I use them at work. The gun-type ones vary in quality and, as you'd expect, accuracy. If you get a good quality Fluke or FLIR branded one I'd trust them on liquids. A Jaycar style unit... not so much.
They also vary in accuracy because they are reliant on an assumed emissivity. This will vary greatly and you will get bogus readings on reflective surfaces like stainless or chrome. For liquids and dull painted surfaces it's a different story, but you still need to set the emissivity.

For example, I attempted to measure the temp of a piece of conveyor at work. The Jaycar unit (colleague's) read 67°C, and the Fluke unit read 52-55°C. The ambient temp was 34°C and it was in the sunlight. I was able to touch and keep my hand on the belt, so it was probably under 50°C. A contact measurement of the belt showed it to be 41°C.

The cheaper units have a habit of going out of calibration over time, whereas the expensive units maintain accuracy for years. Standard stuff.
Once you know and set your emissivity and use it exclusively on liquids, I would trust one. Just be wary that they need to be configured for your application. If it doesn't have a user-set emissivity, I'd be very wary of purchasing it.

 

[davelovesbeer]

Also, if using for hot liquids, any steam that may get on the unit sensor will alter the reading, therefore giving a false result

 

[mje1980]

And if you point them at a 1000c slab of steel they blink and flash

 

[Truman42]

I have a fairly decent one that I purchased through Blackwoods. I use it to check things like...

• Temp of yeast starter in flask prior to pitching into wort.
• Temp of wort through side of fermenter
• Temp of cooled boiled water prior to hydrating dry yeast.

Basically anything that has to stay sanitary and I therefore dont want to go sticking a thermomter into if it can be helped. I wouldnt use it for mash temps or anything like that.

 

[pedleyr]

My understanding is that they only measure the surface temperature, which isn't usually accurate enough for the purpose of mash temperatures etc.

Some people also say that they don't work well on reflective surfaces, but others report no problems. Again, I can only go by what I've read.

 

[TheWiggman]

Depends on the material pedleyr. Infra red is like light (it's all electromagnetic radiation), and as you know light will bounce of some surfaces (like a mirror) and go through others. Clear acrylic is a good example. Light goes straight through it, you can see stuff behind a bit of clear acrylic. Infra red radiation though will reflect off acrylic like a mirror. Using an infra red camera you will see your own reflection on a drink dispensing machine. This makes inspections behind clear windows impossible without a special attachment on some camera models. Mirror stainless behaves the same way - if you point an IR gun at it you'll actually be measuring the temp of whatever is being relected off the surface on the other side of the room.

To address this, surfaces can be painted with a high emmissivity paint which addresses all issues. It's very handy for machined shafts. This would work perfectly on brewing gear.

Likewise, mashing will be difficult if there are bubbles. The temp on the surfaces of the bubbles will be a fair bit less than the actual mash, so you'll get a false reading.

 

[Nizmoose]

I have a reasonably cheap one and have found it adequate for the less crucial measurements (I'm an extract brewer so no need to measure mash temp yet) such as cold crashes, fermentation temperature things like that, my crude check for calibration is to see what sort temp it reads on water that is boiling and water that's just freezing, it seems to be reasonably accurate still it's just a matter of what you want to use it for

EDIT: I should also add that I find it extremely useful, definitely beats sticking thermometers in things and having to worry about sanitisation during fermentation and such. I'd definitely recommend getting one even if it's not top of the line depending on what you want to use it for