Sensitron PL4+D

Addressable Loop Inputs - What They Add to a Gas Detection System

Standard gas detection control panels accept 4–20 mA signals from individual detectors wired back to the panel on separate cables. This is reliable and widely understood, but for larger small installations - where multiple detectors are spread across a site - individual wiring runs add installation cost and complexity.

The PL4+D's support for addressable loop inputs provides an alternative: multiple detectors connected on a single loop, with each detector individually addressable by the panel. This reduces cable runs, simplifies installation in multi-point systems, and makes it easier to identify which specific detector in a loop has triggered an alarm. Combined with the RS485 bus as standard, the PL4+D supports broader system integration - connecting to building management systems, SCADA platforms, and site control infrastructure - without additional hardware.

For installations at the upper end of the small system range, or where future expansion is planned, the PL4+D's 12-input capacity and loop capability make it a more scalable choice than the 8-input PL4+.

PL4+D vs PL4+ - Choosing the Right Small System Control Panel

Both the PL4+D and PL4+ are control panels for small gas detection installations, certified to EN 60079-29-1 and compatible with the full Sensitron detector range. The key differences are:

PL4+ - up to 8 × 4–20 mA inputs (4 on board, expandable to 8). No RS485 bus as standard. No SIL rating. The straightforward choice for simple small installations with a limited number of detector points and no loop or RS485 requirements.

PL4+D - up to 12 addressable inputs accepting both 4–20 mA and loop connections. RS485 bus as standard. SIL1 certified. Panel configurator software available. The appropriate choice for installations requiring higher input capacity, addressable loop detectors, RS485 integration, or SIL1 functional safety certification.

If your installation has 4 or fewer detector points and no RS485 or SIL requirement, the PL4+ is likely sufficient. For anything beyond that, or where future expansion is likely, the PL4+D is the more capable and scalable option.

Contact us for system configuration advice

Have a question about the Sensitron PL4+D?

Our technical team can advise on input configuration, loop vs 4–20 mA detector compatibility, RS485 integration, and whether the PL4+D or PL4+ is the right panel for your installation.