Special Functions; Safety Function - Siemens 3RS2 Manual

The following diagnostic states are displayed:
• Sensor wire break
• Sensor short-circuit (resistance sensors)
• Internal device fault
5.4

Special functions

5.4.1

Safety function

The 3RS2 device is designed as a temperature limiter (see Temperature limiter TB (Page 28))
and for the temperature monitoring as a temperature monitor (see Temperature monitor TW
(Page 30)) according to EN 14597.
The mode of action is type 2.B, 2.K, 2.P, 2V (TB), 2.H (TB).
Only sensors tested in accordance with EN 14597 (EN 60730-2-9) may be used to set up a
complete RS (control device) function in accordance with EN 14597.
The 3RS2 evaluation unit sets a reserve of 2 °C for resistance sensors and 3 °C for thermocouples,
i.e. in the during limit violation monitoring, the device would react 2 °C / 3 °C earlier for safety
reasons.
Note
The offset functionality allows calibration of the device.
The calibration of the entire measuring chain, including sensor, must be carried out by the user.
A warning limit value "Overshoot" / "Undershoot" is displayed on an integral LCD. At the same
time the integrated safety-related output switches the system to a safe operating state.
The safety function of the digital device is based on the overshooting and undershooting of
limits and corresponds with:
• SIL 1 (IEC 61508)
• PL c (ISO 13849)
On a digital device 3RS2600 and on digital device with IO-Link 3RS2800 a 3-digit code protects
the "Parameter change" function.
The safety function is based on the quiescent current principle.
Note
Safe state
The basis of the safety function is the definition of the safe state.
In the case of temperature monitoring relays, this is the "OFF state", i.e. an open contact for
sensors or shutdown of the actuators.
3RS2 temperature monitoring relay
Equipment Manual, 02/2022, A5E42462552002A/RS-AB/002
Digital devices
5.4 Special functions
27