Inductive sensors enhance safety

The sensors ensure that stabiliser legs are fully retracted before the vehicle can be driven, preventing accidental driveaway incidents and protecting both operators and equipment.

Application overview

Mobile cranes, telescopic handlers and similar lifting vehicles rely on extendable stabiliser legs to maintain stability during lifting operations. These hydraulic jacks widen the vehicle’s footprint, preventing tipping when handling heavy loads.

Before the vehicle can be moved, however, it is essential to verify that all stabilisers have been fully retracted. Manufacturers typically achieve this through:

• Cab indicators that alert the operator, or
• Interlocks that prevent the transmission from engaging until the system confirms safe retraction.

The customer’s original system used mechanical limit switches. Although functional, these devices introduced longterm drawbacks:

• Wear and tear from repeated actuation
• Higher lifetime maintenance costs
• Susceptibility to contamination and environmental conditions.

To improve reliability and reduce service requirements, the manufacturer sought a noncontact sensing solution.

Sensor-based solution

Contrinex’s Classic 600 Series inductive sensors provided an ideal upgrade path. The customer selected normally closed, 2wire inductive sensors, installing one on each stabiliser cylinder to detect the presence or absence of a target at the fully retracted position.

Why not wire in series?

At first glance, wiring the sensors in series, mirroring the previous mechanicalcontact arrangement, seems logical. However, inductive sensors introduce a challenge: voltage drop across multiple devices in series can compromise performance.

Parallel wiring for logic control

To overcome this, the engineering team adopted a more robust approach:

• Each sensor is configured as normally closed
• All sensors are wired in parallel
• The resulting configuration creates a logical NAND condition.

This means the system only confirms a “safe to drive” state when every sensor detects its target correctly. If even one stabiliser leg is not fully retracted, the circuit remains open and the vehicle cannot be moved.

Outcome

The switch to Contrinex inductive sensors delivers several operational advantages:

• Zero mechanical wear, thanks to noncontact detection
• Improved longterm reliability in harsh outdoor environments
• Reduced maintenance costs over the vehicle’s lifetime
• Enhanced safety, ensuring stabilisers are always verified before travel.

For manufacturers of mobile lifting equipment, this approach offers a robust, modern alternative to mechanical limit switches. PLUS Automation can help engineers select from Contrinex’s vast range of sensors that align with the industry’s increasing focus on automation, safety integrity and lifecycle efficiency.

Click to download Contrinex’s Product Overview brochure.