Sensitron PL4+ Gas Detection Control Panel

Sensitron PL4+ Gas Detection Control Panel

The PL4+ is an exceptionally cost-effective solution which offers reliable detection of flammable, toxic, and oxygen levels in various marine applications. This panel is particularly suitable for deployment in small marine systems where safety is paramount. Equipped with 4 analog 4-20 mA inputs, expandable to 8 using the PL4/ESP 4-input expansion module, the PL4+ provides flexible monitoring capabilities. This expansion module adds 4 additional inputs and 16 electrical Open-Collector outputs, which can be converted into relays using the 16-relays board. This versatility makes the PL4+ well-suited for a range of marine installations.

The control panel of the PL4+ comes complete with 5 relays, with each relay serving a specific purpose. Three relays are dedicated to the thresholds for flammable, toxic, and oxygen levels, ensuring timely alerts and responses. An additional relay is designated for fault detection, while one programmable relay allows for customizable functionality. These relays ensure effective monitoring and control of safety parameters in marine environments. The PL4+’s LCD display provides a precise indication of gas concentration levels and alarm set points, allowing marine operators to monitor conditions with accuracy. The mode status LED indicators offer clear visual notifications for alarm levels, faults, and power-on status, enabling rapid identification of potential issues.

In the demanding marine industry, audible alarms play a crucial role in ensuring the safety of personnel and assets. The PL4+ features an internal buzzer that emits an audible alarm in case of alarms or faults, promptly alerting the crew to take necessary action. The front panel button allows for manual silencing of the alarm when needed, ensuring flexibility and control in response to changing conditions. To withstand the challenges of the marine environment, the PL4+ is enclosed in an ABS cabinet rated IP65. This robust construction ensures protection against water and dust ingress, guaranteeing reliable operation even in demanding maritime conditions. 

Furthermore, the PL4+ can accommodate a 12 VDC, 7Ah additional battery within its cabinet, ensuring uninterrupted functionality during power supply failures commonly encountered at sea. With its cost-effectiveness, adaptable features, and robust design, the PL4+ is the ideal solution for detecting flammable, toxic, and oxygen levels in small marine systems. Its versatile capabilities make it suitable for a wide range of marine applications, including ships, offshore platforms, and other marine installations where safety and reliable gas detection are essential.

The PL4+ control panel offers three operating modes, which can be easily selected using the key located on the front panel:

  1. System ON: This mode activates the system and enables its full functionality.
  2. System OFF: In this mode, the system is completely deactivated, ensuring no operation or monitoring takes place.
  3. System in programming mode: This mode allows users to access and modify the system’s programming parameters.


To provide clear visual indications, the PL4+ is equipped with an LCD display featuring two rows and sixteen columns. This display presents essential information such as gas concentration readings and alarm set points in a concise and readable format. For visual status indications, the control panel incorporates seven LEDs. A green LED indicates the power supply status, ensuring users are aware of the system’s operational state. Two yellow LEDs are dedicated to signaling low battery supply and faults, ensuring prompt attention to potential issues. Furthermore, four red LEDs are allocated for alarm notifications and auxiliary outputs, providing immediate visual alerts for critical conditions.

To supplement the visual indications, the PL4+ includes an acoustic indication feature. A built-in buzzer with a sound level of 70 decibels at a distance of 1 meter ensures that alarms and other important notifications are audibly communicated, alerting personnel to take appropriate actions promptly.

The front panel of the PL4+ is equipped with a user-friendly keyboard, consisting of two buttons:

  1. ACK (Acknowledge): This button allows users to acknowledge and confirm alarms or other system notifications, indicating that the necessary actions have been taken.
  2. Reset: The reset button enables users to reset the system or return it to its default state, facilitating troubleshooting or reverting programming changes if needed.


These front panel buttons provide convenient and straightforward control options, ensuring efficient interaction with the PL4+ control panel.

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