Reflow oven: the temperature probe

First of all, let's meet the oven:
Toaster oven

The oven is a Princess PR2259. It's a 4 liter oven with infared heaters totalling 660W. It is compact but still quite powerful which is good for fast heat changes. The oven comes with a small tray which may come in handy to spread the heat a little over the PCB.
Oven tray

Two IR heaters are present, on the top and on the bottom:
Infrared heaters and grill

No fancy electronics are used in the oven, basically the heaters are connected through a four way switch (to turn elements on and off separately) and a mechanical timer with an annoying bell.


The thermocouple is a wire made of two different metals that are joined at the tip. It is a standard K-type thermocouple:

I decided to keep most of the oven intact since it uses special screws and my el-cheapo screwdriver that fits them can break any minute now. Here is the left side of the oven opened:
Side of the toaster oven opened

A spring mechanism keeps the glass door shut when not opened manually and the two heaters are connected with heat resistant wires. The inside of the oven is attached to the sides by twisting it through short cuts in the side, as you can see below. This is a good place to place put the thermocouple wire through:
Thermocouple wire through the hole

On the outside, the wire comes out at the back.
Thermocouple wire at the back of the oven

I have yet to take a picture of the thermocouple on the inside of the oven, I will put that here later. Next step is the solid state relay box.