Kistler-Morse KM Load Stand II - Manual (Page 27)

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97-1100-01 Rev. H
SYMPTOM POSSIBLE CAUSE SOLUTION
Repeatable Drift
over 24-hour
Period Periodic drift is most likely
caused by thermal expansion
due to sun’s radiation or vessel’s
response to its own heating
cycles.
Problem likely to be noticed
shortly after initial installation
or on system that previously
functioned correctly in cool or
overcast weather.
Loosen nuts on top bolts and inspect top bolts.
• Top bolts free to move in their holes— If vessel is heated, it may be
radiating or conducting heat through vessel legs and affecting Load
Stand sensors.
To reduce head radiation/conduction:
a. Insulate vessel.
b. Contact K-M to discuss adding a high temperature insulating pad.
• Top bolts jammed — Jammed top bolts indicate undersized bolt holes
on vessel mounting flange and/or vessel support movement beyond
limits of Load Stand clearance holes. Resulting side loads affect Load
Stand sensors.
To reduce side loads:
a. Enlarge vessel mounting flange bolt holes to provide additional
clearance.
b. Contact K-M to discuss adding a sliding pad if support movement
exceeds 0.125” (3mm).
If support movement and heat radiation/conduction have been eliminated as
source of error and periodic drift still indicates system is not meeting
specifications (Appendix A), contact K-M.
NOTE: If keeping long-term records, take level readings at same time each
day to minimize error.
Sudden Change
in Weight Reading
or System
Requires Frequent
Recalibration Sudden change in weight reading
can be caused by a broken Load
Stand, causing indicated weight
to shift up or down by large
amount, up to 100% of full-scale
live load.
Problem likely to be noticed on
system that previously functioned
correctly.
Check voltage outputs of individual Load Stands (refer to Chapter 2,
Pre-Check Procedures, the section titled Method 1: Measuring Output).
Voltage should be between -750 mV and +750 mV on installed Load Stands.
If not, check Load Stand resistance as described above in Problem 1.
Sudden change in weight reading
can be caused by problems with
signal processor.
Problem likely to be noticed
shortly after initial installation
or on system that previously
functioned correctly.
Check signal processor excitation voltage and incoming AC voltage for
accuracy and stability (refer to signal processor manual).