CWT Weighing Equipment Operation & Calibration 4 — Questions and Answers
Question 1: What is the primary purpose of the 'tare' function on a weighing instrument?
- To increase the scale's maximum capacity
- To subtract the weight of a container so only the net contents are displayed (Correct answer)
- To perform a span calibration
- To lock the reading for recording
Correct answer: To subtract the weight of a container so only the net contents are displayed
The tare function offsets the display by the weight of an empty container, allowing the scale to show only the net weight of material added afterward.
Question 2: When inspecting a load cell cable for potential errors, a technician should look for all of the following EXCEPT:
- Pinched or kinked cable insulation
- Moisture ingress at the connector
- The cable color matching the platform color (Correct answer)
- Shield continuity to ground
Correct answer: The cable color matching the platform color
Cable color has no bearing on performance; pinching, moisture ingress, and shield grounding are all real sources of signal error.
Question 3: A legal-for-trade retail price-computing scale must display price-per-unit and total price. Under NIST Handbook 44, the computed price must be:
- Always rounded up to the nearest cent
- Accurate within the value of one minimum price increment (Correct answer)
- Displayed in font no smaller than 0.5 inch
- Verified only during initial installation
Correct answer: Accurate within the value of one minimum price increment
NIST HB 44 requires that computed prices not exceed the value of one minimum price division in error, protecting both buyer and seller.
Question 4: Which action should a CWT technician take if a scale's as-found calibration data shows it was operating outside tolerance at the previous inspection interval?
- Recalibrate and continue without documentation
- Document the out-of-tolerance condition, assess impact on prior measurements, and report per applicable procedures (Correct answer)
- Immediately condemn and remove the scale from service permanently
- Increase the calibration interval to reduce future findings
Correct answer: Document the out-of-tolerance condition, assess impact on prior measurements, and report per applicable procedures
Out-of-tolerance as-found data triggers an impact assessment and nonconformance documentation to evaluate whether prior weighing results were affected.
Question 5: What does OIML stand for in the context of weighing equipment standards?
- Organization for International Measurement and Logistics
- Organisation Internationale de Métrologie Légale (Correct answer)
- Office of Industrial Metering and Labeling
- Operational Instrument Maintenance and Licensing
Correct answer: Organisation Internationale de Métrologie Légale
OIML is the Organisation Internationale de Métrologie Légale, the intergovernmental body that issues international recommendations for legal metrology including weighing instruments.
Question 6: A technician calibrates a scale using test weights that have not been recertified in five years. What metrology principle does this violate?
- Traceability — calibration standards must be traceable to national standards through an unbroken chain with stated uncertainties (Correct answer)
- Resolution — the display must show enough decimal places
- Repeatability — results must be consistent across multiple trials
- Reproducibility — different operators must get the same result
Correct answer: Traceability — calibration standards must be traceable to national standards through an unbroken chain with stated uncertainties
Metrological traceability requires that all reference standards used for calibration be periodically recertified and traceable to national or international measurement standards.
Question 7: In a multi-range scale, when the applied load crosses the transition point into the higher range, what happens to the scale division (d)?
- The scale division decreases for greater precision
- The scale division increases, reducing resolution in the higher range (Correct answer)
- The scale division stays the same across all ranges
- The indicator automatically switches to a different unit of measure
Correct answer: The scale division increases, reducing resolution in the higher range
Multi-range scales use finer divisions (smaller d) in lower ranges and coarser divisions (larger d) in higher ranges, trading resolution for extended capacity.
CWT Weighing Equipment Operation & Calibration 4
What is the primary purpose of the 'tare' function on a weighing instrument?