Troubleshooting Sensor-Related Problems - Siemens SITRANS FC430 Operating Instructions Manual

10.3.2

Troubleshooting sensor-related problems

Incorrect and unstable measurements, especially at low flows, are typically a result of an
unstable zero point due to:
● Incorrect installation
● Bubbles in the liquid
● Vibrations/Cross talk
● Solid particles settling in the liquid
In the following a 4-step guide to troubleshooting is provided:
Step 1
Step 2
Step 3
Step 4
The guide will enable you to trace the reason for incorrect measurements and to improve the
application.
Step 1: Inspecting the application
Ensure that:
1. The sensor is installed as described in Installing/mounting (Page 41).
2. The sensor is located in a vibration-free position. Vibrations can disturb the sensor and
therefore cause measurement error.
Depending on application, you should furthermore ensure the following:
● Liquid application
Ensure that the sensor is filled with liquid and liquid only.
Air or gas bubbles in the liquid cause instability and can result in measurement errors.
Flush the pipe systems and the sensor for several minutes at maximum flowrate to remove
any air bubbles which may be present.
Note
The liquid must be homogeneous in order to measure with high accuracy. If the liquid
contains solid particles of greater density than the liquid, then these solids can settle,
especially at low flow rates, which will cause instability in the sensor and lead to
measurement errors.
For pastes or process fluids with suspended solids always orient the sensor vertically with
flow in upward direction to maintain solids suspension.
● Gas application
Ensure that the gas pressure/temperature conditions contain sufficient superheat to prevent
dewing or precipitation. If the gas contains vapor or droplets then these may precipitate,
causing instability.
FC430 (From firmware 4.0)
Operating Instructions, 06/2017, A5E39789392-AA
Preliminary application inspection
Zero point adjustment
Measurement error calculation
Application improvement
Diagnosing and troubleshooting
10.3 Operation troubleshooting
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