IR temp sensor emissivity

If you're going to be measuring the temperature under the same conditions and materials etc... you should just set the emissivity to give the correct temperature and leave it.

All IR sensors will have a variable emissivity adjustment, unless the temperature is above a certain limit - such as 200 *C where the emissivity becomes less of a source of error. After all the emissivity is only of concern when measuring temperatures from a low temperature source i.e. room temperature.

John.

i do not exactly understand what you mean by 'same conditions and materials' , but I am measuring a weld which is an alloy so, I guess it is the same material that I am measuring over and over again. And as regards the conditions, do you mean ambient conditions? Yes, they will stay the same.

However, the IR sensor that I am looking at, has a fixed emissivity (0.95) at temperatures below 200C. And the temperatures I am looking to measure are below 200C. So could this instrument be a source of error for me?

thanks for your input!

Emissivity is specific to each material.

Buy an adjustable one and see the effects.

Emissivity adjustment will give you more precision but other factors such as your measurement spot size may be even more important.

Vscid, if you're looking for a deviation from a known good welding temperature then I don't think you need to bother with emissivity, as you will be comparing like with like, so the emissivity isn't going to vary much between measurements.

To be honest I doubt if you will need the variable emissivity and in fact it may just complicate the measurement you are making?

Hope this is of some help - John.

You should have a variable emissivity, you may not always be welding on the same material. Also when reading the preheat temperature you should verify the temperature a certain distance from the weld, and there may a difference is conditions, ie. the weldment may not be cleaned of oxidation or protective varnish or other coatings.

When you take a reading on the shiny weld material you get one reading while you will get another reading on the less shiny uncleaned area. (one hundred degrees or more).

Variable emissivity IR sensors allow you to adjust the Emissivity to the correct Emissivity for that object. you can get a precise answer from Bob Harris (rharris@exergen.com)