const int analogInPin = 1;  // Analog input pin that the 3.3V sensor is attached to
int sensorValue = 0;        // value read from the sensor
int outputValue = 0;        // Output value for the DAC
const int dacPin = PIN_DAC0; //4-20mA loop DAC pin

void setup() {
    analogWriteResolution(12); //set DAC resolution for 4-20mA loop (12bit 0-4095 = 3.8-20.7mA)
    analogReadResolution(10); //set ADC resolution for sensor 
}

void loop() {
  
  sensorValue = analogRead(analogInPin); // read the sensor
  outputValue = map(sensorValue, 0, 1023, 0, 4095); //map sensor value to optimal scale for output
  analogWrite(dacPin, outputValue);  // write scaled value to the 4-20mA loop 
  delay(2);
}

Most sensors can be up and running in less than 5 minutes

Harnessing the power of the Arduino community you are most likely to find a ready working library for your specific sensor online which outputs the sensor value to the Serial terminal. To have this sensor data output via the 4-20mA loop you can use the simple map() function in the Arduino IDE to scale the sensor date over the full 4-20mA range. Then simply write the scaled value to the on-board DAC and you have just made a 4-20mA sensor!

Caution

• To achieve the minimum 4mA on the loop,  the 3.3V sensor should not consume more than 15mA averaged (The transmitter has significant capacitance on the sensor supply rail, so short higher current peaks can absorbed, depending on the duration and interval). Higher average current is supported and will not damage the transmitter, it will only raise the minumum controllable loop current above 4mA, thus reducing your range and resolution.
• Due to the non-isolated nature of the transmitter we recommend that you use a USB isolator for programming and calibration via the USB port.