Dual Flow Meter (see hardware video at: https://youtu.be/110fMAtmgmk)

DualFlowMeter.ino

// Copyright (c) 2014 Jeff Barriault
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
// and associated documentation files (the "Software"), to deal in the Software without restriction, 
// including without limitation the rights to use, copy, modify, merge, publish, distribute, 
// sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is 
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or 
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
// NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//
// Interupt driven liquid flow rate sensor
// Connect signal (yellow) line to arduino digital pin 2/3. red to vcc and black to gnd.
#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 7, 6, 5, 4);

int ftPin = 2;
int gbPin = 3;

volatile int pulseCount;

float calFactor = 4.8;
float convFactor = 3.78541178; // 1 US gallon per minute = 3.78541178 liters per minute
float flowRate; 
unsigned int frac;

void increment() 
{ 
  pulseCount++;
} 

float getFlowRate(int interrupt)
{
  pulseCount = 0;
  attachInterrupt(interrupt, increment, RISING);
  sei();          //Enables interrupts
  delay (1000);   //Wait 1 second
  cli();          //Disable interrupts
  detachInterrupt(interrupt);
  return ((pulseCount / calFactor) / convFactor); // convert to GPM
}

void setup()
{ 
  pinMode(ftPin, INPUT);
  pinMode(gbPin, INPUT);
  
  lcd.begin(16, 2);
} 

void loop ()    
{
  flowRate = getFlowRate(0);

  lcd.setCursor(0, 0);
  lcd.print("FT: ");
  lcd.print(int(flowRate), DEC);
  lcd.print(".");
  frac = (flowRate - int(flowRate)) * 10;
  lcd.print(frac, DEC);
  lcd.print(" GPM     ");
  
  flowRate = getFlowRate(1);

  lcd.setCursor(0, 1);
  lcd.print("GB: ");
  lcd.print(int(flowRate), DEC);
  lcd.print(".");
  frac = (flowRate - int(flowRate)) * 10;
  lcd.print(frac, DEC);
  lcd.print(" GPM   ");
}