CST Weights & Measures Certification 2 — Questions and Answers
Question 1: What is the maximum allowable error (MAE) for a Class III commercial scale used at a retail checkout with a capacity of 30 lb?
- ±0.01 lb
- ±0.02 lb (Correct answer)
- ±0.5 lb
- ±1 lb
Correct answer: ±0.02 lb
NIST Handbook 44 specifies that Class III scales have an MAE of one scale division, and a 30 lb capacity Class III scale typically has 0.01 lb divisions making the MAE ±0.01 lb at the zero end, but ±0.02 lb across mid-range divisions — 0.02 lb is the standard mid-range MAE.
Question 2: Under NIST Handbook 44, which test is used to evaluate a scale's ability to return to zero after loading and unloading?
- Shift test
- Repeatability test
- Return-to-zero test (Correct answer)
- Sensitivity test
Correct answer: Return-to-zero test
The return-to-zero test verifies that a scale's indication returns to zero (or the initial no-load reading) after a load is applied and removed.
Question 3: A weights and measures inspector finds a scale with a 'Cardinal' brand name on the nameplate but no NTEP Certificate of Conformance number. What is the appropriate action?
- Approve the scale if it passes field tests
- Reject the scale immediately and cite the owner
- Verify if the scale model appears on the NTEP Approved Products List (Correct answer)
- Replace the nameplate and retest
Correct answer: Verify if the scale model appears on the NTEP Approved Products List
An inspector should check the NTEP (National Type Evaluation Program) database to confirm whether the specific model is type-approved, as the absence of a CC number on the plate does not automatically mean the device is non-compliant.
Question 4: Which of the following statements about tare on a commercial scale is correct under Handbook 44?
- Tare must always be subtracted before any transaction
- Tare capability must not exceed the scale's capacity (Correct answer)
- Tare is only permitted on Class I laboratory balances
- Tare indication must be displayed in red on digital scales
Correct answer: Tare capability must not exceed the scale's capacity
Handbook 44 requires that the tare mechanism cannot set a tare value beyond the scale's maximum capacity, ensuring the net weight indication remains meaningful.
Question 5: What does the term 'scale division value (d)' refer to in metrology?
- The number of divisions on the analog dial
- The smallest unit of measurement the scale can display (Correct answer)
- The tolerance allowed between two consecutive readings
- The weight of the scale platform itself
Correct answer: The smallest unit of measurement the scale can display
The scale division value (d) is the value of the smallest increment displayed or printed by the indicating or recording element of a scale.
Question 6: Which U.S. federal agency has primary oversight authority for weights and measures at the national level?
- OSHA
- NIST (Correct answer)
- FTC
- EPA
Correct answer: NIST
The National Institute of Standards and Technology (NIST) provides the technical standards and handbooks that underpin U.S. weights and measures regulation.
Question 7: A retail grocery store scale displays net weight as 2.00 lb but the actual net weight using certified test weights is 1.96 lb. The scale division is 0.01 lb. Is this scale within tolerance?
- Yes, it is within the 2% tolerance
- No, the error of 0.04 lb exceeds the MAE for this scale (Correct answer)
- Yes, because the error is less than one pound
- No, but only if the scale is used for meat
Correct answer: No, the error of 0.04 lb exceeds the MAE for this scale
For a Class III retail scale with 0.01 lb divisions, the MAE is typically one division (0.01 lb), and 0.04 lb error is four times that value, placing the scale out of tolerance.
CST Weights & Measures Certification 2
What is the maximum allowable error (MAE) for a Class III commercial scale used at a retail checkout with a capacity of 30 lb?