Endress+Hauser iTEMP TMT82 HART 7 - Device Behavior in Case of Range Violation Category (F, S, M)

Temperature transmitter iTEMP TMT82 Appendix
Endress+Hauser 33
Two-channel functions
Two sensors can be connected to the transmitter and the transmitter can be operated in
the following safe functions:
• Averaging function:
The measured values M1, M2 of the two sensors are output as an arithmetic average
(M1+M2)/2.
• Difference function:
The measured values M1, M2 of the two sensors are output as a difference (M1-M2).
• Backup function:
If a sensor fails, the transmitter automatically switches to the other measuring channel.
For this the sensor types must be identical, e.g. two 3-wire RTD Pt100 sensors. The
backup function is used to increase availability or improve the diagnostic capabilities.
Therefore the following types of sensor are permitted in the SIL mode:
• 2x thermocouple (TC)
• 2x RTD, 2/3-wire
• Sensor drift function:
If redundant sensors are used, the long-term drift of a sensor can be detected, for
instance. This is a diagnostic measure as the signal of the second sensor is only used for
this diagnostic. If identical sensors are used, the backup function can also be used.
Recommendation: set the "Drift/difference alarm delay" parameter to 5 seconds.
The configured drift/difference set point should be at least twice the safety accuracy
value.
SIL 3 configuration: homogeneous redundancy
Two temperature transmitters with one sensor per transmitter are required for a SIL 3
measuring point. The measured values of the two transmitters are evaluated in a logic unit
using a safe voter. →  9,  33
RTD/TC
RTD/TC
2
2
3
4
1
=
CMP
Fail-safe
PLC/PCS
A0053697
 9
Example with current output at the first transmitter and current output and HART
®
communication at the
second transmitter. PLC/process control system voting of both sensor values: SIL 3
1 2 temperature sensors
2 2 temperature transmitters
3 4 to 20 mA current output
4
4 to 20 mA current output, optionally with HART
®
communication
7.1.2 Device behavior in case of range violation category (F, S, M)
The safety function is used to monitor the measured value. In the SIL mode, an error
current or saturation current is output in the event of a measurement outside a user-