About Oven's Temperature Controls
Ovens are one of those appliances that we spend some time choosing, a lot of time using but very little time thinking about. Like refrigerators, they have few working parts---but those parts are so critical that it's usually easier to buy a new appliance than to replace the part. Conventional control systems work the same way whether they control slow cookers, home or commercial ovens. Differences are based on the type of fuel they use and how they use it. Does this Spark an idea?
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History
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The concept of the oven is ancient---a contained space, heated so that it cooks food. Whether devised from pits in the ground or stone boxes, the first ovens were heated by fire---wood burned until the sides of the space were too hot to touch. The brick ovens of northern Europe are still popular in upscale restaurants and pizza parlors. They use the same wood fire fuel, although their engineering is a bit more sophisticated than earlier models. The wood-fired oven entered the industrial age in a cast iron "stove"; a large appliance with compartments for the wood fire that heated an oven, a warming box and surface plates that could be removed for high heat. Controlling wood-fired ovens and stoves took some practice but it was easy. You just had to know how much wood to burn and how long to burn it to reach the desired temperature for cooking.
Types
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Today's ovens use gas or electricity to heat the area inside a metal container, often insulated to minimize heat loss. Both technologies were developed during the 20th century as transmission and transportation networks made their use practical and economical. For much of the century, what type of fuel was used depended on which was more locally available and less expensive. In the last quarter of the century, microwave and convection ovens became popular, addressing some of the problems of the earlier types of ovens.
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Features--Conventional Oven Controls
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Conventional oven controls have two components--a thermostat and a switch. Electrical controls operate using either thermocouple or digital regulators that respond to a command from a manual dial or digital display on the face of the control panel, connecting or breaking the circuit for electricity to get through high-resistance steel or ceramic "elements" inside the oven. Gas oven controls signal an "igniter" to spark flame when the thermostat signals that the temperature has fallen below the command entered on the control panel or on the manual dial.
Features--Non-Conventional Oven Controls
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Controls for convection and microwave ovens also start motors for fans (convection ovens) or to rotate turntables. The command entered on the control panel of a convection oven sets a thermostat that either starts the heating or stops it. Convection ovens use heat that is circulated by a fan, so the control system uses either thermocouple or electronic regulators to start the heating process and the fans to circulate it. Microwave ovens use electromagnetic waves generated by a magnetron tube and the control panel controls the amount of electricity that is transmitted through the relay system to this tube. The oven operates by regulating the flow of electricity to the magnetron rather than by responding to a thermostat.
Considerations
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Both electric and gas oven controls start and stop the supply of fuel, which leads to rising and falling temperatures in the oven. The electromagnetic waves of microwave ovens heat most unevenly and are the hardest to control. Convection ovens, although using electricity for fuel, are more economical and heat more evenly than other types.
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