What should never be connected together in loops?

What should never be connected together in loops?

• A. Active to passive
• B. Passive to active
• C. Active to active or passive to passive
• D. Passive to passive

Answer: (C)

In a 4-20 mA loop, there is typically one active current source driving the loop and all other devices act as passive loads that simply draw current. The loop current is set by that single active device and flows through every device in series. Connecting two active devices together would put two current sources in the same loop, causing them to fight each other and create unpredictable readings or damage. Connecting two passive devices together means multiple sinks with no single driver, which can require more loop voltage than the source can provide and upset or cut off the current. The safe and functional arrangement is one active device paired with passive loads. So, the best practice is to avoid connecting two actives or two passives in the same loop; single active with passive devices is the correct pattern.

In a 4-20 mA loop, there is typically one active current source driving the loop and all other devices act as passive loads that simply draw current. The loop current is set by that single active device and flows through every device in series.

Connecting two active devices together would put two current sources in the same loop, causing them to fight each other and create unpredictable readings or damage. Connecting two passive devices together means multiple sinks with no single driver, which can require more loop voltage than the source can provide and upset or cut off the current. The safe and functional arrangement is one active device paired with passive loads.

So, the best practice is to avoid connecting two actives or two passives in the same loop; single active with passive devices is the correct pattern.