Vehicle Scale Systems & Applications Flashcards

What is weigh-in-motion (WIM) technology primarily used for in vehicle weighing applications?

Answer: Screening or identifying potentially overweight vehicles without requiring them to stop

WIM systems screen vehicles at highway speeds to flag potentially overweight vehicles for further static inspection; they are generally not approved as standalone legal-for-trade devices.

What is the primary operational difference between a portable axle scale and a full-platform truck scale?

Answer: Portable axle scales weigh only individual axles sequentially, while platform scales weigh the entire vehicle simultaneously

Portable axle scales measure one axle group at a time and sum the readings, while full-platform (truck) scales capture the entire vehicle weight in a single or multiple drafts simultaneously.

When testing a vehicle scale for repeatability, what is the correct procedure per standard weights and measures practice?

Answer: Apply the same test load at least three times and verify that all readings fall within the allowable tolerance

Repeatability testing requires applying an identical test load a minimum of three times to confirm the scale provides consistent readings within tolerance on each application.

What is the most common cause of rocking or instability in a vehicle scale deck?

Answer: Improper load cell mounting, unlevel check rods, or uneven foundation support

Deck instability (rocking) is most frequently caused by uneven support at load cell mounting points, improperly adjusted check rods, or differential settlement in the foundation.

What is the function of a check rod (restraint rod) on a vehicle scale deck?

Answer: A mechanical rod that limits horizontal movement of the deck while allowing free vertical deflection for weighing

Check rods are mechanical restraints that prevent excessive lateral or longitudinal movement of the scale deck while permitting the free vertical movement needed for accurate weight measurement.

What is 'zero drift' in a vehicle scale, and what typically causes it?

Answer: A gradual shift of the zero reference point caused by temperature changes, load cell fatigue, or foundation settlement

Zero drift is a slow change in the scale's unloaded reference point over time, most commonly caused by temperature fluctuations, load cell creep or fatigue, and long-term foundation settlement.

What is 'shift error' (cornerloading error) in a vehicle scale, and how is it detected?

Answer: Non-uniform weight response across different areas of the deck; detected by a shift test placing test weights at multiple deck positions

Shift error refers to non-uniform sensitivity across different zones of the scale deck, and is revealed by a shift (section) test in which a known test weight is repositioned to different locations on the deck.