#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // REGISTER SELECT PIN,ENABLE PIN,D4 PIN,D5 PIN, D6 PIN, D7 PIN
int analogInput = A0;
float vout = 0.0;
float vin = 0.0;
float R1 = 100000.0; // resistance of R1 (100K) 
float R2 = 10000.0; // resistance of R2 (10K) 
int value = 0;
void setup(){
   pinMode(analogInput, INPUT);
   lcd.begin(16, 2);
   lcd.print("DC VOLTMETER");
}
void loop(){
   // read the value at analog input
   value = analogRead(analogInput);
   vout = (value * 5.0) / 1024.0; 
   vin = vout / (R2/(R1+R2)); 
   if (vin<0.09) {
   vin=0.0;//statement to quash undesired reading !
} 
lcd.setCursor(0, 1);
lcd.print("INPUT V= ");
lcd.print(vin);
delay(500);
}

Vout = Vin * R2 / (R1 + R2 )

R2 = Vout * R1 / (Vin – Vout)

#include<LiquidCrystal.h>
LiquidCrystal lcd(12,11,5,4,3,2);   //rs,e,d4,d5,d6,d7
int Vin=5;        //voltage at 5V pin of arduino
float Vout=0;     //voltage at A0 pin of arduino
float R1=3300;    //value of known resistance
float R2=0;       //value of unknown resistance
int a2d_data=0;    
float buffer=0;            
void setup() 
{
 lcd.begin(16,2);
}
void loop()
{
  a2d_data=analogRead(A0);
  if(a2d_data)
  {
    buffer=a2d_data*Vin;
    Vout=(buffer)/1024.0;
    buffer=Vout/(Vin-Vout); 
    R2=R1*buffer;
    lcd.setCursor(4,0);
    lcd.print("ohm meter");
    lcd.setCursor(0,1);
    lcd.print("R (ohm) = ");
    lcd.print(R2);
    
    delay(1000);
  }
}

 V = IR

 I = V / R

#include<LiquidCrystal.h>
LiquidCrystal lcd (12,11,5,4,3,2);
 
void setup() {
// put your setup code here, to run once:
lcd.begin(16,2);
lcd.clear();
}
 
void loop() {
// put your main code here, to run repeatedly:
int voltage_value0 = analogRead(A0);
int voltage_value1 = analogRead(A1);
 
 int subraction_value =(voltage_value0 - voltage_value1) ;
 float temp_val = (subraction_value*0.00488);
 
 float current_value = (temp_val/22);
lcd.setCursor(0,0);
 lcd.print("current value=");
 lcd.setCursor(0,1);
 lcd.print (current_value);
 lcd.print("A");
 delay(1000);
}

Vout = (Vin × R2) / (R1 + R2)
Vin = Vout * ((R1+R2)/R2)
Vin = Vout * ((10+2.2)/2.2)
Vin = Vout * 5.55

Vout = ADC Reading * (5/1023)
Vin =  ADC Reading * 0.00488 * 5.55
Vin =  ADC Reading * 0.027

Gain = Vout / Vin = 1 + (Rf / Rin)

 I = Vsh/Rsh 
Vsh = Vout / Gain = Vout /21
Vout = ADC Reading * (5/1023) = ADC Reading * 0.00488
I = ADC Reading * (0.00488/ 21) /0.22 = ADC Reading * 0.0011

/*
 * Wattmeter using Arduino
* Potetnital divider to measure voltage -> A3
 * Op-Amp output to measure current -> A4
 */
 
#include <LiquidCrystal.h>  //Default Arduino LCD Librarey is included 
int Read_Voltage  = A3;
int Read_Current  = A4;
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2; //Mention the pin number for LCD connection
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
void setup() {
  lcd.begin(16, 2); //Initialise 16*2 LCD
  lcd.print(" Arduino Wattmeter"); //Intro Message line 1
  lcd.setCursor(0, 1);
  lcd.print("  With Arduino  "); //Intro Message line 2
  delay(2000);
  lcd.clear();
}
void loop() {
 
 float Voltage_Value = analogRead(Read_Voltage);
 float Current_Value = analogRead(Read_Current);
 Voltage_Value = Voltage_Value * 0.027;
 Current_Value = Current_Value * 0.0011;
 lcd.setCursor(0, 0);
 lcd.print("V="); lcd.print(Voltage_Value); 
 lcd.print("  "); 
 lcd.print("I=");lcd.print(Current_Value); 
 float Power_Value = Voltage_Value * Current_Value;
 lcd.setCursor(0, 1);
 lcd.print("Power="); lcd.print(Power_Value); 
 
delay(200);
}

 int reading=analogRead(sensor);

float temperature=reading*(5.0/1023.0)*100;

/*-----------Arduino LM35 Code-------------*/
/*-----------Digital Thermometer Using Arduino-------------*/
#include<LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // REGISTER SELECT PIN,ENABLE PIN,D4 PIN,D5 PIN, D6 PIN, D7 PIN
#define sensor A0
byte degree[8] = 
              {
                0b00011,
                0b00011,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000,
                0b00000
              };
void setup()
{
  lcd.begin(16,2);
  lcd.createChar(1, degree);
  lcd.setCursor(0,0);
  lcd.print("    Digital    ");
  lcd.setCursor(0,1);
  lcd.print("  Thermometer   ");
  delay(4000);
  lcd.clear();
}
void loop()
{
  /*---------Temperature-------*/
     int reading=analogRead(sensor);
     float temperature=reading*(5.0/1023.0)*100;
     delay(10);
  
  /*------Display Result------*/
    lcd.setCursor(2,0);
    lcd.print("Temperature");
    lcd.setCursor(4,1);
    lcd.print(temperature);
    lcd.write(1);
    lcd.print("C");
    delay(1000);
}

 void setup()
{
analogReference(INTERNAL);
}

 void setup()
{
analogReference(EXTERNAL);
}

Temperature = (adc*5000/1023)/10;

Temperature = (adc*1100/1023)/10;