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
What phenomenon occurs when a piezoelectric crystal is mechanically stressed and generates an electrical charge?
Answer: The direct piezoelectric effect
The direct piezoelectric effect describes the generation of electrical charge in a crystal when mechanical stress is applied.
A load cell has a rated output of 2 mV/V. With a 10 V excitation, what is the full-scale output signal?
Answer: 20 mV
Full-scale output = rated output × excitation = 2 mV/V × 10 V = 20 mV.
Which material is most commonly used as the piezoelectric sensing element in industrial force sensors?
Answer: Quartz (SiO₂)
Quartz is the most widely used piezoelectric material in industrial sensors due to its stability, high modulus, and negligible pyroelectric effect.
In a load cell with remote sense wiring (6-wire connection), what do the sense leads measure?
Answer: The actual excitation voltage at the load cell terminals
Remote sense leads allow the indicator to measure and compensate for voltage drop in the excitation supply leads, ensuring the load cell receives the correct excitation.
What is 'hysteresis error' in a strain gauge load cell?
Answer: The difference in output between increasing and decreasing load at the same load value
Hysteresis is the difference in output readings at the same applied load when approached from increasing versus decreasing load directions.
A load cell's zero balance specification is expressed as ±1% of rated output. For a 2 mV/V cell at 10 V excitation, what is the maximum allowable zero offset?
Answer: ±0.2 mV
Full-scale output = 2 mV/V × 10 V = 20 mV; 1% of 20 mV = 0.2 mV maximum allowable zero offset.
What is the primary purpose of a Zener diode barrier (zener barrier) when installed between an indicator and a load cell in a hazardous area?
Answer: To limit the energy that can reach the hazardous area to intrinsically safe levels
Zener barriers clamp voltage and limit current to prevent ignition-capable energy from reaching classified hazardous locations.