Description
The TXMA is a rail temperature sensor for railway applications, manufacturer type Müller STSBA. It measures the temperature of the running rail and provides the measured value that controls the point heating system.
The housing fits rail profiles S 49, S 54, UIC 60, and R 65 without modification. It is fastened with a clamp and counter-clamp using an M10 threaded rod of strength class 10.9, tightening torque 68 Nm; installation must be below the heating element, otherwise, the sensor will measure the heating system instead of the rail. The housing measures 68 × 64 mm, is fully potted, made of material x 25 CrNiSi 18.9 and weighs approximately 1.5 kg; the operating temperature ranges from -40 … +85 °C, optionally -50 … +105 °C.
There is no plug: The connection cable H07BQ-F, 2 × 1.5 mm² is led out of the potting via a PG 11 screw connection. The output is galvanically isolated, the insulation voltage is 1500 VAC for 60 s – in the track, where traction currents and return current flow, this is the decisive value.
A Pt100 in 4-wire Class A configuration is installed in the housing as the measuring element. The measuring range is configurable and set ex works to -30 … +60 °C, the resolution is 0.1 °C, and the measurement deviation is less than ±0.05 % of the measuring span. The output is 4 … 20 mA in 2-wire technology, reversible to 20 … 4 mA, with output limits 3.8 … 20.5 mA according to NAMUR. The sensor is powered with 9 … 36 VDC.
Note before ordering: A railway standard is not documented – the sheet refers to a "Technical Approval from Deutsche Bahn AG" but does not provide a number or date, and EN 50121, EN 50155, and EN 45545 are not mentioned; proof of compliance must be requested from the manufacturer before use in railway applications. The 1500 VAC for 60 s is insulation voltage, not continuous operating insulation; an overvoltage category and lightning protection are not specified. The data sheet does not state a degree of protection – the housing is fully potted, an IP code is missing. To change the measuring range, the configuration set with DTM-Control software is required, connection via RS 232-C; if configured during operation, the connection to the point heating control is interrupted, and whether the set is still available must be clarified with the manufacturer. A CE mark and explosion protection are not documented.
Advantages at a Glance
- Fits S 49, S 54, UIC 60, and R 65 without modification
- Pt100 4-wire Class A, resolution 0.1 °C
- 4 … 20 mA, reversible to 20 … 4 mA, limits 3.8 … 20.5 mA according to NAMUR
- Galvanically isolated, insulation voltage 1500 VAC for 60 s
- Housing 68 × 64 mm stainless steel, fully potted, approx. 1.5 kg
- Clamp with M10 threaded rod, tightening torque 68 Nm