Damping; Loss Of Echo (Loe); Fail-Safe Mode - Siemens SITRANS LR260 Operating Instructions Manual

When the instrument is returned to M M easurement mode, the transceiver resumes
operation. The reading and mA output default to the last measurement taken. The reading
and associated outputs migrate to the current process level at a rate controlled by the
response rate (2.2.7. 1 ).
If SITRANS LR260 is left in P P ROGRAM mode for 10 minutes without input, it automatically
reverts to M M easurement mode.

Damping

A damping filter smooths out the response to a sudden change in level. This is an
exponential filter and the engineering unit is always in seconds. The setting can be
2.2.4.3.2. Damping Filter
modified in
Damping example
Level (m)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
1 2 3 4
Series1
input
smoothed
(level) output

Loss of Echo (LOE)

A loss of echo (LOE) occurs when the calculated measurement is judged to be unreliable
because the echo confidence value has dropped below the echo confidence threshold.
If the LOE condition persists beyond the time limit set in
displays the Maintenance Required icon, and the text region displays the fault code S S : 0
and the text LOE.
If two faults are present at the same time, the fault code, error text, and error icon for
each fault are displayed alternately. For example, Loss of Echo and Fail-safe High.
S: 0 LOE

Fail-safe Mode

The purpose of the Fail-safe setting is to put the process into a safe mode of operation in
the event of a fault or failure. The value to be reported in the event of a fault is selected so
that a loss of power or loss of signal triggers the same response as an unsafe level.
Page 96 SITRANS LR260 (HART) – INSTRUCTION MANUAL
.
Time (s)
5 6 7
Series2
S: 52 FAIL-SAFE
time constant = 2 seconds
input (level) change = 2 m
In 5 time constants the output rises
exponentially:
from 63.2% of the change in the
first time constant, to almost 100%
of the change by the end of the 5th
time constant.
2.4.1. Fail-safe Timer
the LCD
7ML19985KE02