CST Analog & Digital Scale Technology 3 — Questions and Answers
Question 1: According to NIST Handbook 44, what is the maximum number of scale divisions (n) allowed for a Class III commercial scale?
- 1,000
- 5,000
- 10,000 (Correct answer)
- 100,000
Correct answer: 10,000
NIST Handbook 44 allows Class III scales a maximum of 10,000 scale intervals (n), balancing resolution with accuracy requirements for commercial use.
Question 2: In analog dial scales, the term 'graduation' refers to:
- Process of calibrating the scale to a known standard
- Individual marks on the dial face representing weight increments (Correct answer)
- Distance between the pointer pivot and the dial face
- Total weighing capacity of the scale
Correct answer: Individual marks on the dial face representing weight increments
A graduation is each individual division mark on the scale dial or chart, with the interval value defining the smallest readable increment.
Question 3: Which test is used to detect a digital scale's ability to return to zero after a load is removed?
- Discrimination test
- Shift test
- Return-to-zero test (Correct answer)
- Repeatability test
Correct answer: Return-to-zero test
The return-to-zero test verifies that after removing a test load, the indicator reading returns to the same zero reference within tolerance.
Question 4: A spring scale reads 4.95 lb when a certified 5.00 lb test weight is applied. The error expressed as a percentage of the applied load is:
- −0.5%
- −1.0% (Correct answer)
- −2.0%
- +0.5%
Correct answer: −1.0%
Error = (4.95 − 5.00) / 5.00 × 100 = −1.0%, meaning the scale under-reads by 1%.
Question 5: What is the function of an analog-to-digital converter (ADC) in a digital weighing indicator?
- Amplifies the load cell excitation voltage
- Converts the continuous millivolt signal from the load cell to a digital numeric value (Correct answer)
- Stores calibration constants in non-volatile memory
- Controls the display refresh rate
Correct answer: Converts the continuous millivolt signal from the load cell to a digital numeric value
The ADC samples the analog mV/V load cell signal and converts it to a digital number that the microprocessor can process and display as a weight.
Question 6: Hysteresis in a weighing scale is best described as:
- Error that increases proportionally with temperature
- Difference in readings between loading and unloading at the same applied weight (Correct answer)
- Random fluctuation in the last display digit
- Offset between the printed capacity and the tested capacity
Correct answer: Difference in readings between loading and unloading at the same applied weight
Hysteresis is the path-dependent error where the scale reads differently for the same load depending on whether the load was approached from below or above.
Question 7: Which OIML accuracy class requires the smallest minimum load cell verification interval (v min)?
- Class C (industrial)
- Class B (precision)
- Class A (special) (Correct answer)
- Class D (coarse)
Correct answer: Class A (special)
OIML Class A (special precision) instruments have the strictest tolerances and require the smallest verification interval, supporting the highest resolution measurements.
CST Analog & Digital Scale Technology 3
According to NIST Handbook 44, what is the maximum number of scale divisions (n) allowed for a Class III commercial scale?