CWT Weighing Equipment Operation & Calibration 2

Question 1

What is the purpose of a 'span calibration' on a weighing instrument?

Accepted Answer

To adjust the sensitivity so the instrument reads correctly at a known non-zero load

Answer

Span calibration adjusts the instrument's sensitivity/gain so that it accurately reads a known test weight applied above zero.

Question 2

Which environmental condition most commonly causes 'thermal drift' errors in load cell-based scales?

Accepted Answer

Temperature changes affecting load cell output

Answer

Temperature changes alter the electrical resistance and mechanical properties of load cells, causing their output to drift from the calibrated value.

Question 3

A technician places test weights on a scale and finds the reading is 0.5 lb low at mid-span but accurate at full capacity. This is most likely caused by:

Accepted Answer

Non-linearity or a linearity calibration error

Answer

A reading that is off at one point but correct at another indicates a linearity error, meaning the instrument's response is not proportional across its range.

Question 4

What is the recommended practice before performing a calibration on a vehicle scale in cold weather?

Accepted Answer

Allow the scale to stabilize at ambient temperature for at least one hour

Answer

Allowing the scale to stabilize ensures that thermal gradients within the structure have equalized, providing a stable baseline for accurate calibration.

Question 5

Under NIST Handbook 44, what is the term for the difference between the actual value applied to a weighing device and the indicated value?

Accepted Answer

Error

Answer

Error is defined as the indicated value minus the actual value (or vice versa depending on convention) and is the fundamental measurement of instrument accuracy.

(CWT) Certified Weighing Technician Practice Test

(CWT) Certified Weighing Technician Practice Test

CWT Weighing Equipment Operation & Calibration 2