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Topic: Mass flow meter (Read 1 time) previous topic - next topic

Zee.Alam

Thanx lefty
i got u
tomorrow i will implement this on CNG dispenser
n then let u know...
Thanx again

Regards,
Zee

Saad Khalil

Hello Brother..
if it is really changing current from 4-20mA and you only need to plot this change using Arduino then i think it must be simple, give that data pin to an analog pin 0 and put this program into your Arduino and open up the serial monitor so it will plot you the change of 4 to 20 into 0 to 1024 pieces as ADC in Arduino is 10 bit.
Code: [Select]

/*
  Circuit:
   > Data pin connected to analog pin 0.
   > Ground on CNG Board is connected to Ground of Arduino
*/

int dataPin    = A0;
int dataValue = 0 ;
void setup()
{
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
}

void loop()
{
  // read the data value:
  dataValue = analogRead(dataPin);
  // print the results to the serial monitor:
  Serial.print("Data = " );                       
  Serial.print(dataValue);     

  // wait 10 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(10);                     
}
Saad Khalil

retrolefty

Quote
Are there any 4-20mA devices that are NOT loop powered?  I though that was the whole point of 4-20mA.  The 4mA floor is the minimum power required for the device to output "zero".


Yes there are. In the process control world they are sometimes called "4-wire transmitters", where two of the wires are for a input power supply for the transmitter, and the other two wires are the now 'powered' 4-20ma current loop output. This allows measurement of the loop at the 'receiver' end to just use a passive 250 ohm resistor, with one of the wires also grounded to the measurement systems ground.

So a 2-wire 4-20ma transmitter device requires that the loop is powered externally, while a 4-wire transmitter can power the loop.

Lefty

kmkn



Yes there are. In the process control world they are sometimes called "4-wire transmitters", where two of the wires are for a input power supply for the transmitter, and the other two wires are the now 'powered' 4-20ma current loop output. This allows measurement of the loop at the 'receiver' end to just use a passive 250 ohm resistor, with one of the wires also grounded to the measurement systems ground.

So a 2-wire 4-20ma transmitter device requires that the loop is powered externally, while a 4-wire transmitter can power the loop.

Lefty


So in 4 wire system for arduino is the positive is connect to 5v pin and negative wire to 250ohm and then to analog pin? thanks

retrolefty

Quote
So in 4 wire system for arduino is the positive is connect to 5v pin and negative wire to 250ohm and then to analog pin? thanks


That doesn't sound correct at all. Without a link to a specific 4-wire device you are talking about it's hard to speculate.

Lefty

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