In: Electrical Engineering
There are wide variety of transducers that can sense and control the temperature in an microwave oven. A few of them are 1.thermocouples which are based on seebeck effect which is when two junctions of dissimilar metals comes into contact a voltage s induced in it.
2.A temperature which is actually connected to the wall of the microwave oven button. when you push the button and enter the temperature to be set, the probe will read it and once the temperature which is set is reached, it shuts off the oven.
3.infrared sensor which reads the temperature values in the form of heat produced by the radiation of electromagnetic waves.
4.A thermistor. this transducer can do both sensing and controlling.
i'm going to use the thermistor as it has the advantage of controlling voltage by setting the temperature.
explanation: A thermistor typically is a resistor which has a negative coefficient of temperature which means as temperature increases, the resistance will decrease. so by using the thermistor with another resistor in voltage dividing mode, followed by an amplifier, we can control both the temperature and voltage at the same time.
To understand above explanation even more, lets see an example below with the circuit which can be used to both sense and control.
As you can see from above circuit the output is being generated according to the temperature being set. the output of the opamp will be then fed to the stepup transformer which will give its output to magnetron which creates the high voltages and necessary heat. when the set temperature is reached, the breaker will cutoff the supply to the thermistor which will stop the operation.of the oven.
Hope this helps.
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