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Operating
8.3 Characterization chart
Fail-safe
The fail-safe parameters ensure that the device defaults to an appropriate state when a valid
level reading is not available. (See Fault codes and corrective actions (Page 159) for a list of
fault codes related to fail-safe.)
• Parameter "Fault current" defines the behavior (mA output value to report) when an error
condition, such as loss of echo, is detected.
• A fail-safe timer also activates when an error condition is detected. "Fail-safe LOE timer" sets
the amount of time the loss of echo will persist before device enters fail-safe mode.
• Upon expiration of the timer, and if device is still in an error condition, the mA output value
reported is based on value set in parameter "Fail-safe loss of echo".
If fail-safe operation activates frequently, see Diagnostics and troubleshooting (Page 155).
8.2
mA control
Parameter
Lower saturation limit
Upper saturation limit
Verifying the mA range
Check that the external device can track the entire 4 to 20 mA range sent by the device.
Follow the steps below if actual mA readings differ between the device (shown under "Loop
current" in measurement view of device) and an external device (such as a PLC).
1. To test the loop current, run the "Loop test wizard". Select a constant mA value to use in the
test from a list of mA values, or set a custom mA value by selecting option "User", then set a
value.
2. Check that the external device displays the same mA reading as the mA value set above.
3. If external device reading differs from the value manually set on the device, adjust the
reading on the external device to match the reading on the device.
8.3
Characterization chart
If you wish to measure volume and you cannot use a pre-defined vessel (Vessel shape (2.5.1)
(Page 123)), you must configure a custom application.
Configure a custom application by setting parameter "Operation" (in quick commissioning
wizard), or "PV selection" (in navigation view) to option "Custom", then define your
vessel/PMD using Customized characteristic curve (2.6.2) (Page 126).
Up to 32 breakpoints, each consisting of an input and output value (X- and Y-value), are
available to define your vessel shape.
• For a custom volume characteristic curve, X-values refer to level, Y-values refer to volume.
86
Default value
Description
3.8
Set lower limit for saturation range, past which the
loop current cannot decrease.
20.5
Set upper limit for saturation range, past which
the loop current cannot increase.
SITRANS LR500 series with mA/HART
Operating Instructions, 03/2024, A5E51099898-AA
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Table of Contents
Troubleshooting
