CST Vehicle Scale Systems & Applications 3

Question 1

What is the purpose of trim (summing) resistors in a vehicle scale junction box?

Accepted Answer

To balance individual load cell outputs so each cell contributes equally to the combined signal

Answer

To increase the total signal output voltage from the load cell network

Answer

To protect load cells from voltage transients and electrical surges

Answer

To convert the millivolt load cell signal into a digital pulse for the indicator

Question 2

What minimum insulation resistance should be measured between load cell signal wiring and the scale structure (ground) to ensure proper operation?

Accepted Answer

1,000,000 ohms (1 MΩ) or higher

Answer

10 ohms or higher

Answer

1,000 ohms (1 kΩ) or higher

Answer

100,000 ohms (100 kΩ) or higher

Question 3

When performing an 'as-found' test on a vehicle scale, what information does the technician document?

Accepted Answer

The condition and accuracy of the scale before any adjustments or calibration are performed

Answer

Whether the scale can safely handle its maximum rated capacity load

Answer

The zero balance of the scale after removing all vehicles and cleaning the deck

Answer

The accuracy of the weight indicator display under laboratory conditions

Question 4

Why is maintaining the correct excitation voltage critical in a multi-load-cell vehicle scale system?

Accepted Answer

Load cells are ratiometric devices whose output depends on excitation voltage, so incorrect voltage causes proportional weight errors

Answer

It determines the maximum weighing capacity supported by the scale

Answer

It controls the display refresh rate and digit brightness of the weight indicator

Answer

It determines how quickly the scale reading stabilizes after a vehicle drives on

Question 5

What physical condition is most likely indicated when a vehicle scale shows a negative weight reading with no load on the deck?

Accepted Answer

Debris, frost heave, or an obstruction beneath the deck is lifting it and relieving the load cells

Answer

The scale has correctly auto-tracked to zero after the last vehicle departed

Answer

The indicator requires a firmware reset to correct a calibration register error

Answer

The excitation voltage supplied to the load cells is set too high

Question 6

What is the typical full-scale rated output of a standard strain gauge load cell used in vehicle scales, expressed in millivolts per volt (mV/V)?

Accepted Answer

1 to 3 mV/V

Answer

0.1 to 0.5 mV/V

Answer

10 to 30 mV/V

Answer

100 to 300 mV/V

Question 7

When a vehicle is weighed in multiple drafts (axle groups sequentially), what is the acceptable variation between the sum of the individual draft weights and a single gross vehicle weight reading?

Accepted Answer

Within the cumulative scale tolerance, typically ±1 division per draft measurement

Answer

Zero — the sum of drafts must exactly equal the single gross weight reading

Answer

Within 100 lbs regardless of scale capacity or division size

Answer

Within 5% of the total gross vehicle weight