Pressure & temperature sensors
Pressure and temperature sensors are measurement devices used in railway rolling stock and infrastructure to monitor the operational state of braking systems, traction equipment, cooling circuits and pneumatic systems.
Pressure sensors measure fluid pressure — pneumatic or hydraulic — within a defined system. Temperature sensors measure the thermal state of components including axle box bearings, brake disc surfaces, power electronics and coolant circuits.
In railway service, these devices must operate across extreme temperature ranges — typically −40°C to +125°C for rolling stock — while resisting vibration, shock, moisture, contamination and electromagnetic interference.
The mechanical environment on bogies and axle boxes requires engineering measures to decouple sensitive electronics from pressure ports and connectors, maintaining calibration over long service intervals.
Key applications
Brake system monitoring is the dominant application for both sensor types on rolling stock. Pneumatic brake systems — standard on European freight wagons and widely used on passenger vehicles — require continuous brake cylinder and brake pipe pressure monitoring to confirm correct application and release of braking force.
Pressure transmitters are distributed across multiple vehicles in a consist, with readings fed to the vehicle control system and, where integrated, to fleet management platforms.
Bearing temperature monitoring identifies overheating that indicates lubricant failure or internal bearing damage. Wayside Hot Box Detectors — infrared pyrometers mounted beside the rail — measure the bearing housing temperature of passing vehicles, generating alerts when readings exceed threshold values.
On vehicles equipped with onboard condition monitoring, thermocouples or resistance temperature detectors (RTDs) provide continuous bearing temperature data throughout a journey.
Traction and auxiliary system monitoring covers the cooling circuits of traction motors, traction inverters and auxiliary power converters. Continuous temperature and pressure data keeps equipment within operating limits and enables early detection of developing faults. Pneumatically actuated pantograph systems are monitored with pressure sensors to verify correct operating force before the pantograph is raised.
Automatic lubrication systems — which deliver lubricant to wheel flanges and rail in curves — are monitored with pressure sensors to confirm correct delivery rate and system integrity.
Qualification standards
The primary qualification standards are EN 50155 (electronic equipment for rolling stock, covering temperature range, power supply quality and electromagnetic compatibility), EN 61373 (shock and vibration requirements), EN 45545-2 (fire protection) and EN 50121-3-2 (electromagnetic compatibility).
Category 3 of EN 61373 applies to sensors mounted on axles or bogies — the highest mechanical stress category in the classification.
The MONITOR project — documented by SNCF Group and launched in 2023 by SNCF Rail Logistics Europe, Wabtec and RDT13 (Régie des Transports des Bouches du Rhône) — demonstrated integrated onboard sensing on freight wagons, transmitting brake cylinder pressure, axle temperature and vibration data in real time to support predictive maintenance on vehicles that previously operated without any onboard monitoring.