Many of us burn our tongue while taking hot tan and coffee. So to solve this problem we can use this simple thermometer which will let you know the status or temperatures of your coffee before drinking it. For measuring the temperature you have to just dip the sensor into you tea or coffee. For that, install the sensor inside the empty pen which will serve as a probe for you.You can set the temperature according to your requirement from 0 degree to 100 degree Celsius.This circuit is based on two IC namely CA3130 and LM35. LM35 works as a sensor to detect the amount of heat present with few more components. IC CA3130 is an operational amplifier which combines the advantage of both CMOS and bipolar transistor on a single chip. Operating voltage range varies from 5V to 16V.  

Digital Thermometers are slowly replacing the conventional mercury thermometer due to the ease of taking reading. People often have the misconception that it contains mercury. Digital Thermometers are mercury free. These thermometers contain thermistor inside the tip which is used to measure the temperature. They provide quick and highly accurate results over the body temperature range. These thermometers are easy to read with LCD display on them. They are equipped with beep alarm & memory function and can record a wide range of temperature. Doctor’s thermometer which are mostly used can read temperature between 94oF and 105oF (35oC and 42oC). It is three in one thermometer as it can record oral, auxiliary and rectal temperatures.