Pressure and temperature sensors used in rail
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, while temperature sensors measure the thermal state of components including axle box bearings, brake disc surfaces, power electronics and coolant circuits.
Within onboard sensors and measurement, they are the most widely fitted devices — embedded wherever a fluid, a bearing or a power circuit must be monitored.
In railway service, these devices must operate across extreme temperature ranges — with sensing elements exposed to conditions well beyond the EN 50155 cabinet classes, which top out at +85°C — while resisting vibration, shock, moisture, contamination and electromagnetic interference.
The mechanical environment on bogies and axle boxes requires mechanical decoupling of the 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 — rely on brake cylinder and brake pipe pressure to confirm correct application and release of braking force, a function traditionally verified through manual brake testing before departure.
Onboard sensing now adds continuous, automated pressure monitoring across multiple vehicles in a consist, with readings feeding the vehicle control system and, where integrated, 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, pantograph and lubrication systems
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 and power supply quality, with electromagnetic compatibility verified to EN 50121-3-2), EN 61373 (shock and vibration requirements) and EN 45545-2 (fire protection).
Category 3 of EN 61373 applies to sensors mounted on the axle assembly — the highest mechanical stress category in the classification — while Category 2 covers bogie-mounted equipment.
Field deployment
The MONITOR project — launched in February 2023 by Wabtec, Fret SNCF and RDT13 (Régie des Transports des Bouches du Rhône), and now coordinated by Rail Logistics Europe (SNCF Group), Wabtec and the Régie des Transports Métropolitains for Aix-Marseille — is fitting freight wagons with sensors transmitting brake cylinder pressure, axle temperature and vibration data in real time.
As of 2026, the technology is being tested on a limited number of wagons under real operating conditions, aiming to bring predictive maintenance to vehicles that previously operated without any onboard monitoring.