CWT Weighing Equipment Operation & Calibration 5

Question 1

What is 'hysteresis' in the context of load cell performance?

Accepted Answer

The difference in output between loading and unloading at the same applied load

Answer

Hysteresis is the phenomenon where a load cell gives slightly different outputs for the same applied load depending on whether the load is increasing or decreasing.

Question 2

According to NIST Handbook 44, what is the maximum allowable tolerance for a Class III commercial scale (e.g., a retail grocery scale) at 500 scale divisions?

Accepted Answer

1 division

Answer

For Class III devices, NIST HB 44 specifies a maintenance tolerance of ±1 division (d) for loads up to 500d.

Question 3

A moisture analyzer uses an internal balance mechanism combined with a drying heater. To ensure weighing accuracy, the instrument should be:

Accepted Answer

Leveled and allowed to warm up per manufacturer specifications before use

Answer

Moisture analyzers contain sensitive internal balances that require proper leveling and thermal stabilization before accurate measurements can be made.

Question 4

A forklift scale (on-board weighing system) shows erratic readings when the forklift engine is running. The most likely cause is:

Accepted Answer

Electromagnetic interference or vibration from the engine affecting load cell signals

Answer

Engine vibration and EMI from ignition/alternator systems are common sources of signal noise in on-board vehicle weighing applications.

Question 5

Which of the following correctly describes the relationship between 'accuracy class' and 'number of scale intervals (n)' for a weighing instrument?

Accepted Answer

Higher accuracy class instruments are permitted more scale intervals (finer resolution) relative to capacity

Answer

OIML and NIST classify weighing instruments such that higher accuracy classes (I, II) are permitted more scale intervals than lower classes (III, IIII), reflecting their superior resolution capability.

(CWT) Certified Weighing Technician Practice Test

(CWT) Certified Weighing Technician Practice Test

CWT Weighing Equipment Operation & Calibration 5