Loss Of Echo (Loe); Loe Timer; Failsafe Mode - Siemens Sitrans PROBE LU Instruction Manual

• When Echo Lock is Off, SITRANS Probe LU responds immediately to a new
measurement (within the restrictions set by the Maximum Fill / Empty Rate).
However, measurement reliability is affected.
• When Maximum Verification or Material Agitator is selected, a new measurement
outside the Echo Lock Window must meet the sampling criteria.
• When Total Lock is selected, Echo Lock Window is pre-set to 0, and the window is
automatically calculated after each measurement.

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.
The LOE timer starts running, and if the LOE condition persists beyond the time limit set by
the LOE timer, the Reliable Echo indicator is replaced by the Unreliable Echo indicator.
Reliable Echo indicator
Unreliable Echo indicator: border flashes when LOE is pending.
When LOE is active, border is solid and text region displays S: 0
Upon receiving a reliable echo, the loss of echo condition is aborted, the Reliable Echo
indicator replaces the Unreliable Echo indicator, and the reading returns to the current
level.

LOE Timer

The LOE timer determines the time (in minutes) to elapse after the last valid reading
before Failsafe mode is activated. When the LOE timer expires, the material level to be
reported is determined by Failsafe Mode.

Failsafe Mode

Failsafe mode defines the reaction of the device if a Failsafe condition is detected. It may
be triggered by a loss of echo, a bad configuration, or certain device faults. If Failsafe
mode is activated by a fault, the instrument will go into Failsafe mode without delay (see
Acyclic Extended Diagnostics (General Fault Codes)
You can select can select one of three possible values to be reported when a Failsafe
condition occurs:
• Default value (Failsafe value) used as output value.
• Storing last valid output value.
• Calculated output value is incorrect.
Page 36 SITRANS Probe LU (PROFIBUS PA) – INSTRUCTION MANUAL
on page 30).
7ML19985JB02