Thermal processes need immediate protection when a temperature limit or monitoring fault occurs. The STL50 switches the system to a safe operating state without delay if the permissible limit is reached, or if faults such as probe break, probe short-circuit, device error or supply voltage failure occur.
It operates as STB safety temperature limiter, STW safety temperature monitor or ASTB exhaust gas safety temperature limiter. Inputs support Pt100 in 3-wire connection and thermocouples J, K, N and S, with ranges up to 600.0 °C for Pt100 and up to 1600 °C for Type S. The forcibly guided main relay handles the safety-relevant temperature limit.
Configuration uses front buttons and a graphic LCD display. Error causes appear in plain text, are stored in memory and are supported by an ALARM LED plus a 24 V DC signal for external alarm messages. Certifications to EN 14597, EN 61508 SIL2 and EN ISO 13849 PL d support safety-relevant systems.
The device can be configured as STB, STW or ASTB, with maximum or minimum monitoring depending on the selected safety task.
Input versions support Pt100 in 3-wire connection or thermocouples Type J, K, N and S with integrated cold junction compensation.
The main relay is a forcibly guided SPDT relay for the safety-relevant temperature limit and switches to the safe state in fault conditions.
Versions with 2RAO output include a pre-alarm relay for additional signaling before the safety limit is reached.
The 2RAO version includes a galvanically isolated 0/4..20 mA or 0/2..10 V output with load-dependent automatic changeover.
A contact input allows reset via an external button after fault elimination in limiter operating modes.
Password protection restricts access to safety-relevant configuration parameters and helps prevent unauthorized changes.
The PA6.6 housing mounts on TS35/TH35 carrier rail and uses screw terminals from 0.14..2.5 mm².
