KROHNE TT 51 SERIES EN - Manual (Page 8)

4
SAFETY FUNCTION
8
TT 51 SERIES
www.krohne.com 09/2010 - 4000869801 - AD TT 51 SIL R01 en
1 For some system failures the alarm output will toggle between a high alarm level (≥21.0 mA)
and a low alarm level (≤3.6 mA). For some HW failures the alarm level will be high even though a
low level is configured and for some other HW failures the alarm will go low even though a high
level has been selected.
To prevent a safety system from restart due to the toggling output the system should be setup so
that once an alarm signal has occurred from the safety loop the system shouldn’t go back to
normal run automatically but only manual ("Restart Interlock").
2 System errors = failures in the software or hardware detected by the diagnostics in the
transmitter.
3 The sensor drift function is valid from SW-versions; IPM-SW 01.01.03 and OPM-SW 01.01.04
and hardware versions 5 and later, implemented in transmitters with serial number 1006.xxxxxx
or later. Serial number 1006.xxxxxx means manufactured week 6 in 2010 and this information is
found on the nameplate or it can be read from the transmitter via ConSoft. The software and
hardware versions can be read from the ConSoft software, tab "Device Information".
4.3 Redundancy
For the following configurations:
• 2 x 2w RTD sensors
• 2 x 3w RTD sensors
• 2 x Thermocouple sensors
• 1x Thermocouple sensor and 1 x 3w RTD sensor
• 1x Thermocouple sensor and 1 x 4w RTD sensor (only valid for TT 51 R)
are either "Sensor drift monitoring" function or "Sensor backup" function selectable at a time.
4.3.1 Sensor drift
If the function "Sensor drift" monitoring is selected, a difference between the sensors of more or
equal to the value stated in the configuration will cause the output to go either "Downscale" or
"Upscale" depending on the user configuration. Maximum temperature difference has to be
specified in °C via ConSoft.
Function Active/Not Active Output Alarm level 1
Sensor break Active 4...20 mA / 20...4 mA ≤3.6 mA / ≥21.0 mA
Sensor short Active 4...20 mA / 20...4 mA ≤3.6 mA / ≥21.0 mA
Low isolation Not active - -
System error 2 Active 4...20 mA / 20...4 mA ≤3.6 mA / ≥21.0 mA
Sensor drift (dual
sensor needed) 3
Active/Not Active
selectable
4...20 mA / 20...4 mA ≤3.6 mA / ≥21.0 mA
.book Page 8 Thursday, September 9, 2010 4:19 PM