CST Scale Installation & Calibration Procedures 2 — Questions and Answers
Question 1: When installing a floor scale in a high-traffic forklift area, which foundation requirement is most critical?
- Reinforced concrete rated for the scale's capacity plus dynamic load factors (Correct answer)
- Standard 4-inch concrete slab with no special reinforcement
- Wooden platform with rubber anti-vibration pads
- Steel grating elevated 6 inches above the floor
Correct answer: Reinforced concrete rated for the scale's capacity plus dynamic load factors
Forklift dynamic loads can exceed static ratings significantly, so the foundation must be engineered for both the scale capacity and impact loads.
Question 2: A load cell outputs 2.0003 mV/V at full rated load. The nominal specification is 2.0000 mV/V. What is the sensitivity error?
- 0.015% (Correct answer)
- 0.015 mV/V
- 0.0015%
- 1.5%
Correct answer: 0.015%
Sensitivity error = (2.0003 - 2.0000) / 2.0000 × 100% = 0.015%.
Question 3: Which NIST Handbook 44 requirement governs the minimum number of test weights needed for a complete calibration of a commercial scale?
- Test loads must cover at least the minimum graduated value up to maximum capacity (Correct answer)
- At least 10 test weights must be used regardless of scale capacity
- Only the maximum capacity test weight is required
- Test weights must equal exactly 50% and 100% of capacity
Correct answer: Test loads must cover at least the minimum graduated value up to maximum capacity
HB44 requires that test loads used span from the minimum test load through maximum capacity to verify accuracy across the full range.
Question 4: During a cornerload test on a 4-load-cell platform scale, one corner reads 2 lb high when 100 lb is placed directly over it. The most likely cause is:
- That load cell has a higher sensitivity than the others (Correct answer)
- The platform is warped
- The junction box summing resistors need adjustment
- All of the above are equally likely
Correct answer: That load cell has a higher sensitivity than the others
Corner errors on individual cells most often indicate sensitivity mismatch; trimming resistors adjust for this once mechanical causes are ruled out.
Question 5: What is the purpose of a 'soak test' performed after scale installation?
- To allow the scale to reach thermal equilibrium and structural settling before final calibration (Correct answer)
- To expose the scale to moisture to check for corrosion resistance
- To apply maximum load for an extended period to test fatigue
- To clean load cell surfaces with solvent before calibration
Correct answer: To allow the scale to reach thermal equilibrium and structural settling before final calibration
A soak test lets the scale stabilize thermally and mechanically so that initial calibration readings are not skewed by transient conditions.
Question 6: On a belt conveyor scale, the 'span calibration' procedure typically involves:
- Running a known test weight chain across the belt at operating speed (Correct answer)
- Placing static test weights on the weigh bridge
- Adjusting the zero with an empty belt only
- Replacing the integrator card and re-zeroing
Correct answer: Running a known test weight chain across the belt at operating speed
Belt conveyor scales use a simulated load (reference weight chain or hanging weights) moved at belt speed to replicate actual material flow for span calibration.
Question 7: Which environmental condition most directly causes 'thermal zero drift' in a load cell scale installation?
- Temperature gradients across the scale structure causing differential thermal expansion (Correct answer)
- High humidity condensing on the display
- Vibration from nearby machinery
- Electromagnetic interference from variable frequency drives
Correct answer: Temperature gradients across the scale structure causing differential thermal expansion
Uneven temperature distribution causes structural members to expand or contract unevenly, mechanically shifting the zero reading independent of any load.
CST Scale Installation & Calibration Procedures 2
When installing a floor scale in a high-traffic forklift area, which foundation requirement is most critical?