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Analytical Scales
Animal Scales
Anti 2 Block
Bench Platform Scales
Boom Angle Sensor
Cable Tension
Checkweighers
Counting Scales
Crane Scales
Crane Scales - Portable
Crane System
Diet and Portion Control Scales
Engineered Products
Floor and Barrel Scales
General Purpose Scales
Hanging Scales
Health / Clinical Scales
Indicators
Laboratory / Balances
Lift Truck Scales
Load Cells / Beams
Mechanical Scales
Moisture Analysis Scales
Monorail and Trolley Scales
Platform Scales
Portion Scales
Postal Scales
Printers
Retail Scales
Services
Sports Scales
Tank Weighing Mounts
Truck Scales
Truck / Car Scales Portable
Veterinary Scales
Wireless Weighing
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Load Cell Troubleshooting |
A) Visual Inspection
Thoroughly inspect cables for cuts or wear and loose or
damaged fittings. Cut or worn cables can cause electrical shorts.
Inspect for distortion or cracks on all metal surfaces. Cracks
may allow moisture penetration also causing electrical shorts.
Any distortion in the load cell itself (bends, twists, etc.)
means the load cell may have been physically damaged. This usually
means it must be replaced. |
B) Resistance to
Ground
Current leak from the load cell's electronics to the load
cell body is usually caused by water entering the load cell
or its cable. Connect all of the input, output, sensing and
ground wires together and measure the resistance between the
load cell body and the wires with a megohmmeter (be sure to
have good contact with the metal load cell sensor). The reading
should be 5000 Megohms or more. If the load cell fails this
test, test again but this time without the ground wire. If the
load cell passes the second test the problem may exist within
the cable or fittings. If the load cell fails both tests, it
requires repair. |
C) Zero Balance Deviation
Residual stress in the sensing area may cause deviations
in the zero balance. It is usually a result of metal fatigue
due to exceeding the load cells capacity or the many lifting
cycles over its life span. Measure the load cell's output with
a millivoltmeter with no weight attached. The output should
be within +/- .1% of rated output. (For example: If the load
cells output is 2 mV/V and the power supply output is 10V, then
the full scale output would be 20 mV. The result is a zero balance
of +/-.1% of rated output. The zero reading should then be within
+/- .02 mV.). Consult your particular load cell specifications
for its output value. If the output is greater than the zero
balance tolerance but less than 50% of the full scale output
the load cell is damaged but may still be serviceable by electronically
're-zeroing' if the electronic indicator with the cell allows
it. However in doing so, the load cell may not remain linear.
If a load cell has more than 50% full scale zero balance shift,
it may require 're-gauging'. |
D) Bridge Resistance
Out of tolerance bridge resistance values may be caused
by the failure of a compensating element. Another cause is a
broken or burned bridge wire. These failures are usually the
result of momentary electrical spikes. Measure the resistance
across each pair of input and output leads. The input and output
resistance is typically 350 +/- 3.5 ohms, Consult your particular
load cell’s specifications for proper resistance and tolerances.
If these readings are out of tolerance the load cell requires
repair. |
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Contact
Netweigh's service department at 1-800-522-2206
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