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Diagnosing and troubleshooting
8.1
Range springs
The range spring establishes the range of sensing head moving beam travel for a given range of
material flow. This spring is installed in the flowmeter sensing head at the factory. The spring is
selected according to the specified design rate of the application.
For best operation, the range spring should provide 0.75 to 2.4 mm (0.030 to 0.094") of moving
beam travel from the static zero to the design rate operation position. The moving beam travel
may be inferred from the value of the LVDT output, as measured between the LVDT green and
yellow wires (or yellow and white wires in the case of a hazardous-rated LVDT unit).
With the 2.5 V AC, 2.9 kHz LVDT excitation supplied:
● 0.75 mm of moving beam movement = 0.188 V AC
● 2.40 mm of moving beam movement = 0.600 V AC
Should the design rate of the flowmeter application change, it may be necessary to reposition
the original range spring, or select and install another range spring, to obtain the optimum
moving beam travel (LVDT output) range. Moving the range spring to a location further away
from the pivot point leaf spring, increases the maximum flowrate capacity.
Range spring removal
1. Observe the range spring mounting position (three positions are available).
2. Loosen the range spring locknut.
3. Remove the range spring mounting bolt and four flange mounting bolts.
4. Remove the range spring from the range spring assembly.
Range spring replacement
1. Install the new range spring in the range spring assembly.
2. Mount the range spring assembly by the four flange mounting bolts.
3. With the moving beam in the static zero position, thread the range spring until the base just
touches the static beam and then turn one complete revolution more.
4. Install the range spring mounting bolt and tighten the range spring locknut.
SITRANS WFS320
Operating Instructions, 02/2016, A5E32880290-AB
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Table of Contents
Troubleshooting
