POWERING YOUR DEVICES

Understanding Device Diagrams

For each device type, you’ll find two diagrams:

• Integral Sensor Devices: These diagrams show devices like pressure transmitters or flowmeters with built-in sensors.
• External Input Devices: These diagrams illustrate devices like isolators, signal converters, temperature transmitters, or frequency transmitters that rely on external inputs.

Where you see “Indicator” or “PLC” in the diagrams, you can substitute any input device, including controllers, alarm systems, loggers, recorders, telemetry systems, and more.

Auxiliary Powered Devices (Four-Wire / Externally Powered)

Auxiliary-powered devices, also known as four-wire devices, require two sets of wires: one pair for power supply and the other for carrying the signal. Common voltage options include 24VDC, 110VAC, or 240VAC. These devices are capable of handling 0-20mA signals and various voltage signals, such as 0-10V, 0-5V, or -10V to +10V.

Loop Powered Devices (Two-Wire / Output Loop Powered)

Loop-powered devices simplify installation by using just two wires for both power and signal transmission. These 24VDC devices always output 4-20mA signals. Be cautious when designing a loop to avoid excessive load. If uncertain, consider using four-wire isolators to re-transmit signals.

Wiring Tip: When connecting a loop, while the power supply’s ‘+’ connects to the device’s ‘+’, all other connections are made ‘-’ to ‘+’. For example, the negative terminal of the two-wire device should connect to the positive terminal of the indicator.

Signal-Powered Isolators (For Temporary Use)