PSM3, PSL, or PSL Plus: Choosing the Right System Monitor

All three monitors display the same P-Bus data. The difference lies in the display size, the operating concept, the mounting cutout — and, in the case of one of them, an integrated tank interface that makes a separate device unnecessary.

NotePSL and PSM3 also display the values of a BullTron battery that is connected directly to the P-Bus — without a battery management shunt. What is displayed in this process is explained in the article Integrating a BullTron battery directly into the P-Bus.

What all three have in common

They serve as both a display and a control unit for the P-Bus. They automatically adapt to the connected components and only show the menus for which data is actually available. Configuration for all three is carried out directly on the device — a computer or configuration software is not required.

All three record data on an SD card, all three come with an M12 T-cable and both P-Bus terminators, and all three can be installed multiple times on board — several monitors display the same data synchronously.

PSM3: compact and fits standard cutouts

The PSM3 has a 3.5-inch TFT display with a glass touchscreen and measures 105 x 105 x 35 mm with a mounting cutout of 88 x 88 mm. This is the deciding factor: 88 x 88 mm is a common cutout size for which many existing switch panels are already prepared.

Its seven submenus cover batteries, tanks, temperatures, AC and DC energy flow, main switches, loads, and bilge pumps. With an operating voltage of 8–64 V DC, it has the widest range of all three devices — relevant wherever higher onboard power supply voltages are involved. The power consumption is 60 mA, and 2 mA in standby mode.

PSL: larger, freely customizable

The PSL features a 5-inch full-color display with a capacitive Gorilla Glass touchscreen, plus a brightness sensor that automatically adjusts the display brightness. It measures 157.5 x 105 x 35 mm with a cutout of 140 x 85 mm — significantly more area than the PSM3, making it not a replacement for an existing 88 mm cutout.

Operation is divided into three pages: Information (battery, tank, temperature, bilge), Energy (DC and AC system including connected inverters), and Control (operating main switches, switching and dimming loads via relay modules). The arrangement of the display elements can be customized as you would on a smartphone; if there are more than eight icons, the display can be scrolled sideways.

The operating voltage is 8–32 V DC, with power consumption of 90 mA and 10 mA in standby.

PSL Plus: with integrated tank interface

Externally and in terms of operating concept, the PSL Plus corresponds to the PSL — same display, same dimensions, same cutout, same operating values. The difference is on the back: up to four tank sensors and two temperature sensors can be connected directly to the display.

This eliminates the need for a separate tank interface, provided you can get by with four sensors. One exception remains: the CMT3 tank interface is still required to connect a flow sensor.

In addition, the PSL Plus can be installed both vertically and horizontally — practical where the panel space dictates the orientation.

NoteThe economics of the PSL Plus depend on the saved interface: if you are monitoring four tanks, you save one device, its installation space, and its wiring. For more than four sensors, the advantage is reversed because a CMT3 would be required anyway.

Deciding based on three questions

1. How large can the cutout be? 88 x 88 mm leads to the PSM3; 140 x 85 mm leads to the two large ones. This question often determines the choice for retrofits alone.
2. How many tank sensors? Up to four and without a flow sensor, this points to the PSL Plus. Beyond that, a CMT3 is needed, and the advantage is lost.
3. What is the onboard power supply voltage? Above 32 V, the PSM3 remains the choice with its 8–64 V DC.

Multiple monitors on board

Since all devices read the same bus data, a second monitor in a different location is possible without additional sensors — typically one at the helm and one in the living area. The measurement is not performed twice, but the same measurement is displayed twice.

This is also the reason why the devices can be mixed: a large monitor as the main control unit, a compact one as a second display. The only requirement is that the bus wiring is correct — meaning it must remain a single line with two terminators.

Typical mistakes during selection

• Deciding based on display size without measuring the cutout. The most common planning error in retrofits.
• Choosing the PSL Plus for more than four tanks. The integrated interface then no longer provides relief.
• Planning a flow sensor for the PSL Plus. The CMT3 remains required for this.
• Planning a second monitor with its own sensors. Unnecessary — all monitors read the same bus data.
• Overlooking the operating voltage. Above 32 V, the PSM3 remains the choice.