Gas Oven Control Systems
The first type of gas ovens you just turned the gas and lit it, very simple and energy efficient with no constant burning pilot, temperature was regulated by opening and closing a gas valve and later a thermostat was added that regulated gas flow.
Second type had a constant burning pilot that heated a thermocouple which generates a very small amount of current which keeps a magnet safety valve open in the control whenever the pilot is burning. This type of control was widely used from around 1940-1960, when you turn on an oven with a TC system the oven comes on instantly and when the oven gets to set temperature the flame just modulates down but does not go out, this type of modulated control were the best baking and had the most constant heat.
Third type used a constant burning pilot that heated a mercury safety valve, when the oven was turned on the pilot size increased and heated the mercury valve sensor and then gas flowed to the main burner. This type control was widely used from 1960 till the end of constant burning Politics ranges only 10 or so years ago. On this system if the pilot blows out the gas for the tiny pilot still flows.
Around 1977 gas ovens started to use hot surface electric ignitors, California banded constant burning pilots in dryers and ranges around 1977, it took till the Obama administration to get this expanded nationwide.
Hot Surface Ignitors are simple but use a good amount of electricity and wear out in 2-10 years depending on how much you use your oven. Replacing HSI is the number one major home appliance today.
There are many other variations of gas oven controls out there, my favorite today is Whirlpools Direct Spark Ignition DSI , this system WP introduced around 1999 and uses a spark like top burners use, it is instant and uses almost no power and should not give any problems in the life of most gas ranges.
John L.