# Temperature Gun

1. Aug 1, 2013

### rollingstein

We have a distillation column with insufficient temperature tappings. In order to do a rough survey of the temperature profile externally an idea is to drill small (say 1 inch) holes in the insulation and take external temperature readings.

Would a IR temp. gun like this one be a good idea?

http://www.thermoworks.com/products/ir/irgun.html#AccessoriesTab

Any other ideas? Anyone try anything similar?

THe unit mentions an ~2% accuracy, is it really that good?

Last edited: Aug 1, 2013
2. Aug 1, 2013

### AlephZero

The basic question you need to answer is "what temperature are you actually measuring".

Clearly the outside temperature of the column, at a point where you removed some thermal insulation, may not be the same as the temperature of what you are distilling. If your column is made of something transparent to visible light, it might not be very obvious what is the source of the IR radiation you are measuring (i.e. is it transmitted through the material of the column, or emitted by the column itself?)

You didn't give any details of the column, and your link to the thermoworks site isn't working right now (my browser says "server not responding") so there are more questions here than answers....

3. Aug 1, 2013

### Staff: Mentor

I'd expect that you will be able to make these cheapie IR guns work just fine in that application. They have several weaknesses, all of which you can correct for:
1) You can't trust the absolute temperature that they report; they're sensitive to the emissivity of the surface they're pointed at. So if you read 130 degrees on a shiny surface and a 150 degrees on a nearby black surface you can't be sure that the temperature difference is really 20 degrees. If both surfaces were black, you'd be fine.
2) The shinier the surface you're dealing with, the less accurate the IR gun is.
3) You can't compare readings taken between two different IR guns.

For your application, you might consider
- After you've made your 1" holes in the insulation, hit the bottom of each one with a spritz of flat black spray paint. That way, they'll be as similar as possible, with a minimum of weird reflective behaviors.
- Put one of your holes near one of your existing temperature tappings with a standard temperature gauge. That way you can check the IR gun reading against a new temperature so you'll know how to interpret the readings at the other locations.

6. Aug 1, 2013

### AlephZero

Thermistors? Unless electrical connections would be a problem because of corrosive chemicals, etc.

7. Aug 1, 2013

### rollingstein

Penetrating the shell is the problem. If you mean thermistors pressed against the metal from the outside, sure, that can work.

But then again, the gun will do pretty close to that, I suppose.