Normal mode is recommended when many devices and/or long cable runs are involved. When using the RJ45 connector on the emonTx V3.4 or the emonPi, the connections are GND: pin 5, power (not switched): pin 2, data: pin 4. GND is available on Screw Terminal 3 and switched power on terminal 5 of the emonTx V3. The data line is connected to an available Arduino digital input or Screw Terminal 6 on the emonTx V3, or DIO 4 on the emonTx Shield. The data output is a 3-state or open-drain port (DQ pin 2) and requires a 4k7 pull-up resistor. In normal mode, each sensor is connected between a power line (V dd pin 3) and ground (GND pin 1), and the data output (DQ pin 2) connects to a third, data, line. Note: The Arduino positive supply rail is referred to as V cc and the positive supply for the DS18B20 as V dd. Only two wires, data and ground, are required. In parasite mode the sensor derives its power from the data line. In normal mode, a 3-wire connection is needed. The sensor can operate in normal or parasite mode. Each sensor identifies itself by a unique serial number.

Multiple sensors can be connected to the same data bus. The sensors have a quoted accuracy of +/-0.5 deg C in the range -10 deg C to +85 deg C. The sensor communicates over a one-wire bus and requires little in the way of additional components. It can be easily connected to an Arduino digital input. The DS18B20 is a small temperature sensor with a built in 12bit ADC. Temperature Sensing Using DS18B20 Digital Sensors 

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