CWT Weighing System Installation & Verification 3

Question 1

In a multi-load cell weighing system, what is the primary function of the summing board (junction box)?

Accepted Answer

To combine and trim individual load cell outputs into a single balanced signal

Answer

To amplify the combined load cell signal to indicator input levels

Answer

To convert digital load cell data to an analog 4–20 mA output

Answer

To distribute excitation voltage from the indicator to each load cell

Question 2

What does 'return to zero' (RTZ) performance testing verify in a weighing system?

Accepted Answer

That the indicator reads zero (within the allowable tolerance) after a test load is removed

Answer

That the indicator automatically powers off after a set period with no load

Answer

That the tare function correctly offsets a known container weight

Answer

That the scale can display and store negative weight values

Question 3

What is 'creep' in the context of load cell performance specification?

Accepted Answer

A change in load cell output signal that occurs over time while a constant load remains applied

Answer

Gradual mechanical noise increase as the load cell warms up during operation

Answer

The slow loosening of load cell mounting hardware under continuous vibration

Answer

Surface corrosion that develops on load cell stainless steel housings over time

Question 4

Which grounding practice is most important when installing an electronic weighing system to prevent measurement errors?

Accepted Answer

Connect all metallic structural members, load cell housings, cables, and the indicator to a single common earth ground point

Answer

Ground only the indicator display unit to the building's electrical ground

Answer

Electrically isolate all load cells from the mounting structure using insulating pads

Answer

Use separate, independent ground circuits for each system component

Question 5

What is the purpose of trim potentiometers installed in a load cell summing network?

Accepted Answer

To balance and equalize individual load cell signal outputs so each cell contributes equally to the total reading

Answer

To increase the total weighing capacity beyond each cell's individual rating

Answer

To protect load cells from overload by shunting excess signal current

Answer

To convert the combined mV/V signal to a 4–20 mA current loop output

Question 6

When verifying a belt conveyor (in-motion) scale, which test directly confirms the system's totalization accuracy?

Accepted Answer

Material test — feeding a precisely weighed reference quantity of material through the system and comparing to the totalizer

Answer

Zero verification test with the belt running empty

Answer

Span calibration using simulated electronic test weights only

Answer

Integrator linearity check using static hanging weights on the weigh idler

Question 7

What is 'hysteresis error' in a weighing system or load cell?

Accepted Answer

The difference in output readings obtained when the same load is approached from increasing load versus decreasing load

Answer

The error caused by ambient temperature changes between the zero and span calibration points

Answer

Signal noise induced by electromagnetic interference from nearby power cables

Answer

The fixed offset between the indicated weight and the true weight at any point in the range