Temperature measurement induction heating aluminium

[neitcho]

Is there a way to measure the temperature in an induction oven for melting of aluminium(700 C). The pyrometer I’m using can’t correctly display the temperature when the system is running because it interferes with the induction field. The non-contact IR-camera has been abandoned because of the insufficient stirring of the material that gives an oxidation layer on the material and therefore inability to correctly measure the temperature. I’ve started to look on a system with thermocouples covered in a sialon tube to protect them from corrosion. Industry workers say that the wires might be induced even though you use shielded and twisted wires.
What’s you opinion on this problem. Any solutions will be happily received.

 

[Danger]

I really don't know anything about this, but I'm going to take a shot at it. Would it be possible to install electrodes at opposite ends of the melt? You might then be able to measure the resistance of the aluminum and deduce the temperature from that?

 

[FredGarvin]

Is your pyrometer aninfrared pyrometer? As long as you have the right emissivity of the surface you are measuring, you should be good. I can't imagine why there would be interference with the inductance. Can you explain what problems you are seeing?

 

[Mech_Engineer]

Is there a way to measure the temperature in an induction oven for melting of aluminium(700 C). The pyrometer I’m using can’t correctly display the temperature when the system is running because it interferes with the induction field. The non-contact IR-camera has been abandoned because of the insufficient stirring of the material that gives an oxidation layer on the material and therefore inability to correctly measure the temperature. I’ve started to look on a system with thermocouples covered in a sialon tube to protect them from corrosion. Industry workers say that the wires might be induced even though you use shielded and twisted wires.
What’s you opinion on this problem. Any solutions will be happily received.

I worked on a project where we used a custom coil to heat an iron sample to well over 1000 C, we just used thermocouples attached to the sample to measure its temperature, we were able to get good data out of them (other than the stray bad thermocouple). We did shield the wire going from the thermocouple though, with a plate of copper between the coil and the thermocouple wire. This was done in a vacuum chamber, so oxidation wasn't an issue, we did end up having to cool the coil with liquid nitrogen though.

 

[amuron]

Induction heating of aluminum is a difficult one to handle with infrared, as you mentioned, as the changing oxide raises havoc with infrared measurement. However, you can work around this with a multi band system, which effectively takes emissivity variation our of the equation. A dual band system can work some of the time, but can still be subject to error.

Although this paper focus on steel, some of the same concepts apply.
http://www.temperatures.com/Papers/3700_22.PDF