Explanation of Block Diagram
1) SENSOR ONE: This is first sensor which uses to sense parameter one. This can be temperature sensor, say LM35. The sensor will be placed on the front panel. One can use LCD display to read the temperature.
2) SENSOR TWO: This is second sensor which uses to sense parameter two. This can be Humidity sensor, say LDR. The sensor will be placed on the front panel.
3) AMPLIFIER: We are going to use LM324 which is having 4 inbuilt amplifiers. Since we have two sensors, we have used this Amplifier.
4) ADC: We are going to use ADC 0808 which is 8 bit and 8 channel ADC. Since we have two inputs for ADC, we have used this ADC.
5) LCD: Liquid Crystal Display which is commonly known as LCD is an Alphanumeric Display it means that it can display Alphabets, Numbers as well as special symbols thus LCD is a user friendly Display device which can be used for displaying various messages unlike seven segment display which can display only numbers and some of the alphabets. The only disadvantage of LCD over seven segment is that seven segment is robust display and be visualized from a longer distance as compared to LCD. Here WE have used 16 x 2 Alphanumeric Display which means on this display WE can display two lines with maximum of 16 characters in one line.
6) EEPROM: We need to store the parameter values in some device. We have chosen EEPROM for this purpose as since it is a non-volatile memory and can hold data after power-off. We can use AT24C02/ AT24C04/ AT24C08/ AT24C16 depending on the memory size requirement.
7) Keypad: We need to display the previous records. So we are going to use a Keypad for this purpose. This keypad can perform various actions like
a) Display previous records
b) Erase previous records
c) Set periodic interval time
d) Send data to PC
e) Set date and time
8) PC Interfacing: We are going to use MAX 232 for the purpose of PC interfacing, using this module, we can send various data like temperature, Humidity if the water to the PC.
9) MICRO-CONTROLLER (89S51): This is the most important segment of the project, i.e. the microcontroller 8052. The controller is responsible for detection and polling of the peripherals status. It is responsible for making. It is responsible for prioritizing all the devices attached to it.
WE have used the ATMEL 89s51 microcontroller. The AT89S51 is a low-power, high-performance CMOS 4-bit microcontroller with 8K bytes of in-system programmable Flash memory. It has got 32 I/O lines, Watchdog timer, two data pointers, two 16-bit timer/counters, six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and a clock circuitry.
It is the major part of the system which controls all the operation of the circuit such as LCD interfacing, square wave generation. It also decides the messages to be displayed on the LCD along with the time duration for which they should be displayed on the LCD. Microcontroller also decides the frequency of square wave output.

Applications:
This electronic circuit can be used for the following application:
1) To calculate and store the temperature and humidity of a boiler in the industry.
2) To store flow of the water flowing from the dam or a canal
3) To monitor / display the level of the liquid inside the container
4) Also this system communicates with a PC and sends various data like level of humidity, liquid flow, and temperature of water.