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Strain Gauge & Piezoelectric Sensors Flashcards

7 cards from real CST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Strain Gauge & Piezoelectric Sensors flashcards as text

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

    Answer: Approximately 2

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

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

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

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

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

    Answer: Static dead loads held for extended periods

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

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

    Answer: Incomplete curing of the adhesive

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

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

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

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

  6. In a shear beam load cell, where are the strain gauges typically bonded?

    Answer: At the point of maximum shear stress, 45° to the beam axis

    Shear beam gauges are bonded at ±45° to the neutral axis where principal strains from shear are maximum, making them sensitive to shear rather than bending.

  7. What is the typical insulation resistance requirement between strain gauge circuits and the load cell housing per OIML R 60?

    Answer: At least 2,000 MΩ

    OIML R 60 requires a minimum insulation resistance of 2,000 MΩ (2 GΩ) between the bridge circuit and the load cell body to prevent leakage errors.