CST Troubleshooting Techniques & Repair Methods 2

Question 1

A digital scale displays a stable reading but consistently shows values 2% above the certified value across its entire range. What is the most likely cause?

Accepted Answer

Incorrect span calibration

Answer

A consistent percentage error across the entire range indicates an incorrect span calibration rather than a hardware fault.

Question 2

When troubleshooting a scale that returns to zero correctly but gives erratic readings under load, what should be checked first?

Accepted Answer

Mechanical binding or restriction of the platform

Answer

Erratic readings under load that disappear at zero typically indicate a mechanical issue such as binding, side loading, or debris under the platform.

Question 3

A technician measures the mV/V output of a load cell and finds it is within specification, but the indicator still reads incorrectly. What is the next logical diagnostic step?

Accepted Answer

Check the indicator's internal calibration and input range settings

Answer

If the load cell signal is correct, the fault lies in the indicator's processing — checking its calibration and input range settings is the next step.

Question 4

A load cell's insulation resistance between the cable shield and signal wires measures 50 MΩ when it should exceed 1000 MΩ. What condition does this indicate?

Accepted Answer

Moisture intrusion or cable damage

Answer

Low insulation resistance between shield and signal wires indicates moisture intrusion or cable damage, which can cause unstable or drifting readings.

Question 5

A vehicle scale gives a correct reading for the first axle but a significantly different total when both axles are on. Which component is most suspect?

Accepted Answer

One or more load cells contributing to only part of the platform

Answer

When a partial-platform reading is correct but the full-platform reading is not, a load cell covering the unloaded section is likely faulty or disconnected.

(CST) Certified Scale Technicians Practice Test

(CST) Certified Scale Technicians Practice Test

CST Troubleshooting Techniques & Repair Methods 2