Thread: Hand Held Infrared Thermometers

Hi AB,

For $20 I'd give it a go. But I don't reckon it's a Australian Brand or Australian made. I've been looking at buying one myself to check the same thing but my VH doesn't get that hot at all even for extended periods of use.

Ben

I bought one similar off ebay a while ago and I'm pretty happy with it. We have a good brand one at work and I compared my cheapie against it and it was within 15 degrees.

It will be supremely useful in the kitchen too. I use it every day for things like checking the pan temp before adding the oil.

We've also looked at these gizmos at work for inclusion in our "take home lab in a suitcase" because students would then be able to safely measure the temp of hot stuff .

The claimed "Precision" ( I think they mean "accuracy") is somewhat optimistic because the results are emissivity dependent and the emissivity in the case of the cheaper ones are typically set to a fixed at a value of 0.95.
This makes it suited to rougher/darker materials but they won't be as accurate on super shiny surfaces and by super shiny I do mean shiny.
What we think of as super shiny is not often the case, just a thin layer of dust or oil makes a big difference.
The uncertainty introduce due to the emissivity was not fully tested but I remember something like +/- 10% covered most of the measurements except for shiny materials.
The cheap units claimed repeatability (this is what science calls "precision") is about right , so for comparative readings (objects in the same field and supposedly st the same temp).

If you can purchase a thermometer with adjustable emissivity these can be more accurate BUT you then need to estimate the emissivity and as this is usually just an estimate this can sometimes lead to as many problems. A neat trick we used was to measure the emissivity was stick a small piece of regular (blackened with a black texta - emissivity~ 0.95) masking tape onto the object being tested and point the thermometer at that. Then by pointing at the object near the masking tape and adjusting the emissivity to read the same temp this would give a reasonably reliable measurement of the emissivity. There are still issues with this as some materials e.g. boiling oil are not compatible with this process and the emissivity varies with temp and some temps may fry a piece of masking tape. Most of the units don't go below emissivity values of 0.1 but this will still cover most materials.

The confusing thing about these units is that they use a laser for pointing, so users who don't read the instructions will get confused by the so called Spot size- distance problem. This means the sampled spot increased with distance.
I used one to measure the temperature of a moving chainsaw chain cutting tips and got all sorts of strange readings until I realised that I had to hold the unit just a couple of cm away from the sensor to get a half decent reading. You can imagine this was not all that comfortable with a moving chain.
With a bearing seal you would need to do the same.
The other problem is that at short distances the spot location indicated by the laser may not be the spot being sampled i.e. there is a parallax problem.

I use a thermocouple (TC) for things like bearings because they are better spot indicators.
Using a TC to calibrate the emissivity covers a wider range of materials e.g. boiling oil and is considered more reliable

I just had a look on ebay for cheap TC units and spotted this.

For a mere $33 you can get an IR thermometer that has a built in adjustable emissivity and a TC that can be used to calibrate the emissivity. These weren't around at the time we did the teasing
see http://www.ebay.com.au/itm/High-Temp...item541989bee8

I might get one just to test how accurate it is!

Our local council has a kit that you can borrow that has one in it, as well as items to measure power consumption and costs of electrical items. plus a couple of other things. Ask if your council has one?
Kryn

Originally Posted by BobL

A neat trick we used was to measure the emissivity was stick a small piece of regular (blackened with a black texta - emissivity~ 0.95) masking tape onto the object being tested and point the thermometer at that.

Black electrician's tape is another "emissivity reference" option I often use with a thermal imaging camera.

Hi bob,
This is the one that I used to do exactly what you are asking when I put a new lip seal in the vertical head on the Dormac mill. It's not running hot at all so I swung over to the plain bearing head on the Jones and Shipman surface grinder. Different story.
I know this doesn't help owing to the cost of the unit but it certainly came up accurate alongside the fire brigade unit.
https://www.ridgid.com/us/en/micro-i...ed-thermometer

Phil
ps. I hope the link works as I am using the phone.

Originally Posted by Steamwhisperer

I know this doesn't help owing to the cost of the unit but it certainly came up accurate alongside the fire brigade unit.

In my limited experience, fireys use thermal imaging cameras, which, while ideally suited to their needs, actually aren't that accurate compared to these IR units.

Originally Posted by RustyArc

In my limited experience, fireys use thermal imaging cameras, which, while ideally suited to their needs, actually aren't that accurate compared to these IR units.

Hi RustyArc,
It may have been his personal unit. I didn't ask.
The thermal imaging camera was pretty cool but only showed hot spots, not how hot.
I should locate the thermometer I used when metal spraying. It may be more accurate again.

Phil

Hi Bob, BobL's description of the issues of emissivity estimation is a good explanation. I have an IR thermometer and it has selectable emissivity but as BobL says, you need to know what to set it to. I usually leave at the default (0.95) reading and just use the result as a "rough ballpark". The black tape is a great idea and one I will try. When I bought mine, there were some on the market that had a narrower sample cone. I choose one with the narrowest, I think it may be 1/12 (I'll have to have another look) but I am very much aware that at 12M it is taking an average temperature of 1 sq metre so a small hot spot will be lost in the sample size. Well OK I'm not going to stand 12M away but it's just an example. The TIC that are used in the fire service have a fixed emissivity of 0.95 and will show a temp reading but it's only a "guide" We don't generally use them for temp measurement because we know it's bloody hot. We use them to as an aid to search & rescue as they show heat variations as a contrasting B&W screen (later models have an enhanced colour image) which allows people, objects and the seat of the fire to be "seen" even through thick smoke. They have pretty much revolutionised the way we do business. In the last 10 years they have come down in price and are now common stowage on most urban pumpers. They still cost about $25K though. Cheers, Simon Edit: PS make sure you get one with a data hold and min/max as sometimes you may not be able to look at the screen while sampling

I just had a look on ebay. They have units there which claim 50/1 sampling angle. The one Phil linked to was also 50/1. Leaves my 12/1 a little "average" pardon the pun!

Jaycar have got them, I bought one for the Dragon to use in her kitchen.

DD

If you just want it for <year I will post you my 3M handheld.

Greg

Originally Posted by Greg Q

If you just want it for <year I will post you my 3M handheld.

Greg

A generous offer Gregory that I can't refuse but only if it's not a pain in the neck to send it.

Good to hear from you again.

Bob.