Here is a production of a digital thermometer that uses only one component (except for the power supply). Although it is very simple, its performance is comparable to that of a general thermometer. The most special is that it can directly read the digital temperature value, which is very intuitive. Below we introduce its production process.
Before you start, you must prepare a digital multimeter or digital voltmeter. If not, you can make a digital voltmeter by referring to it here. If you only have a pointer to test the multimeter, it doesn't matter, as long as there is a 1V voltage file, it can also be used to make a thermometer, but the temperature at this time is displayed as a pointer. The one we mentioned above is a thermometer with one component. This component is the integrated temperature sensor LM35D we will introduce. It uses a temperature sensor and an amplifier circuit on a silicon chip to form an integrated temperature sensor (see Figure 1). 
The LM35D is a temperature sensor with an output voltage proportional to Celsius temperature with a sensitivity of 10mV/°C, an operating temperature range of 0°C to 100°C, an operating voltage of 4-30V, and an accuracy of ±1°C. The maximum linearity error is ±0.5 °C; the quiescent current is 80 uA. The device is a plastic triode (TO-92). 
The biggest feature of this temperature sensor is that it does not require external components, and does not need to be debugged and corrected (calibrated). As long as an external 1V head (such as a pointer or digital multimeter) is connected, it becomes a thermometer (see figure 2).
After connecting the line according to Figure 2, you can test whether the boiling water boiling temperature is 100 (note the atmospheric pressure). Room temperature can also be tested and compared with a mercury or alcohol thermometer.
At this point, the thermometer is ready, how, simple. Still not trying? I used this method (adding a digital voltmeter myself) and made a refrigerator in my own house, which is very cool.
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The temperature probe is made as shown in Figure 3. Three pins were soldered with 200 mm long flexible wires (3 colors), and the external two-component epoxy resin was fixed (this can measure the liquid temperature). 
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