Troubleshooting Techniques & Repair Methods Flashcards
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A scale indicator displays random, non-repeatable digit fluctuations even when no load is applied and the scale is in a vibration-free environment. The load cell checks out correctly. What should the technician suspect?
Answer: Noise or instability in the indicator's analog-to-digital conversion circuit
Random non-repeatable fluctuations with a good load cell point to noise or instability within the indicator's A/D conversion circuit or power supply.
During routine maintenance, a technician finds corrosion on the load cell mounting bolts of a floor scale. What is the recommended corrective action?
Answer: Replace the bolts with stainless steel hardware and re-torque to specification
Corroded mounting hardware should be replaced with appropriate stainless or corrosion-resistant hardware and torqued to the manufacturer's specification to ensure consistent load transfer.
A technician is troubleshooting a checkweigher that rejects product inconsistently. The scale reads correctly during static tests. What is the most likely cause?
Answer: Improper dynamic filter or settling time settings for the line speed
A checkweigher that passes static tests but gives inconsistent results in operation typically has dynamic filter or settling time settings that do not match the production line speed.
When testing a scale with substitution weights, the technician finds the scale reads within tolerance at 1000 lb but reads high at 2000 lb. What does this pattern suggest?
Answer: Non-linearity or incorrect span calibration
An error that increases with load while zero is correct points to non-linearity in the load cell or an incorrect span calibration.
A technician finds that a load cell's rated output is 2 mV/V but measures only 1.6 mV/V at full rated load. The excitation voltage is correct. What does this indicate?
Answer: The load cell may be damaged or have been previously overloaded
A significantly reduced mV/V output at rated load with correct excitation suggests the load cell has been overloaded or damaged, reducing its sensitivity.
A tank scale uses three load cells in a compression mount. After repair, the technician should verify correct load cell orientation by confirming what?
Answer: The positive signal output increases when downward (compressive) force is applied
Confirming that the signal output increases with compressive (downward) load verifies the load cell is mounted in the correct orientation for compression loading.
A technician reseals a legal-for-trade retail scale after adjustment. According to NTEP and Handbook 44 requirements, what must the technician affix?
Answer: A W&M security seal or lead-and-wire seal over the adjustment access
Handbook 44 requires that adjustable parameters of a legal-for-trade scale be secured with an approved security seal to prevent unauthorized adjustment.