CST Strain Gauge & Piezoelectric Sensors 2

Question 1

What is the gauge factor (GF) of a typical metallic foil strain gauge?

Accepted Answer

Approximately 2

Answer

Metallic foil strain gauges have a gauge factor of approximately 2, meaning the resistance change is twice the mechanical strain.

Question 2

In a Wheatstone bridge load cell, what is the purpose of using four active strain gauges instead of one?

Accepted Answer

To increase the output voltage range to measurable levels and cancel temperature effects

Answer

Four active gauges in a full bridge configuration doubles sensitivity and provides inherent temperature compensation through common-mode rejection.

Question 3

A piezoelectric load cell is NOT suitable for measuring which of the following?

Accepted Answer

Static dead loads held for extended periods

Answer

Piezoelectric sensors cannot hold a static charge indefinitely; charge leaks over time, making them unsuitable for measuring sustained static loads.

Question 4

Which bonding defect in a strain gauge installation is most likely to cause creep error in a load cell?

Accepted Answer

Incomplete curing of the adhesive

Answer

Incompletely cured adhesive remains viscoelastic and deforms under sustained load, causing the gauge to creep relative to the flexure element.

Question 5

What does the term 'creep compensation' refer to in load cell design?

Accepted Answer

Trimming the bridge with resistors to offset the mechanical creep of the flexure

Answer

Creep compensation involves adding small resistors or shunts to the bridge network to electronically counteract the mechanical creep characteristic of the elastic element.

(CST) Certified Scale Technicians Practice Test

(CST) Certified Scale Technicians Practice Test

CST Strain Gauge & Piezoelectric Sensors 2