Reading rpm and also reading 5 HX711
#include "HX711.h"

HX711 scale_GS1(A1, A0); 
HX711 scale_GS2(A3, A2);
HX711 scale_GS3(13, 12);
HX711 scale_GS4(11, 10);
HX711 scale_FS(9, 8);

float gs1 = 0, gs2 = 0, gs3 = 0,gs4 = 0, fs = 0;

// read RPM

volatile int rpmcount = 0;
int rpm = 0;
unsigned long lastmillis = 0;

void setup() {
  attachInterrupt(0, rpm_fan, RISING);//interrupt cero (0) is on pin two(2).

  Serial.begin(9600);   //start serial communication

  Serial.println();  Serial.println();  Serial.println();
  Serial.println("/////     WELCOME     ///////");
  Serial.println();

  //set scales
  scale_GS1.set_scale(1324);
  scale_GS1.tare();

  scale_GS2.set_scale(1324);
  scale_GS2.tare();

  scale_GS3.set_scale(1324);
  scale_GS3.tare();

  scale_GS4.set_scale(1324);
  scale_GS4.tare();

  scale_FS.set_scale(1324);
  scale_FS.tare();

  Serial.println("Readings:");
}

void loop() {

rpm_read();

read_loadcell();

}

void rpm_fan(){ /* this code will be executed every time the interrupt 0 (pin2) gets high.*/
  rpmcount++;
}

void rpm_read(){


  unsigned long elapsedTime, localRpm, interruptCount;

  elapsedTime = millis() - lastmillis;
  if (elapsedTime &gt;= 1000) {
    noInterrupts();
    interruptCount = rpmcount;
    rpmcount = 0;
    lastmillis = millis();
    interrupts();   
    localRpm = 15 * 1000 * interruptCount / elapsedTime ;
    Serial.print("RPM =\t"); //print the word "RPM" and tab.
    Serial.println(localRpm); // print the rpm value.
  }


}

void read_loadcell(){

  scale_GS1.power_up();
  gs1 = scale_GS1.get_units();
  scale_GS1.power_down(); 

  scale_GS2.power_up();
  gs2 = scale_GS2.get_units();
  scale_GS2.power_down(); 

  scale_GS3.power_up();
  gs3 = scale_GS3.get_units();
  scale_GS3.power_down(); 

  scale_GS4.power_up();
  gs4 = scale_GS4.get_units();
  scale_GS4.power_down(); 

  scale_FS.power_up();
  fs = scale_FS.get_units();
  scale_FS.power_down(); 

  Serial.print("GS1 :\t");      
  Serial.print(gs1);
  Serial.print("\t GS2 :\t");      
  Serial.print(gs2);
  Serial.print("\t GS3 :\t");      
  Serial.print(gs3);
  Serial.print("\t GS4 :\t");      
  Serial.print(gs4);
  Serial.print("\t FS :\t");      
  Serial.println(fs);
}