Acceleration transducers — common types: Which pair correctly lists two common types of acceleration transducers used in measurement and control?

Introduction / Context:
Accelerometers convert inertial acceleration into an electrical signal. Selecting the correct transducer type is critical for bandwidth, sensitivity, and environmental robustness. This item asks you to identify two common acceleration-sensing technologies from mixed lists that include non-acceleration sensors.

Given Data / Assumptions:

• Focus on mainstream acceleration sensor technologies in industry and labs.
• Ignore niche or legacy servo accelerometers for this basic identification question.
• Assume standard signal-conditioning practices (charge amps for piezoelectric, bridge amplifiers for piezoresistive).

Concept / Approach:
Piezoresistive and piezoelectric accelerometers are both widely used. Piezoelectric types generate charge proportional to force (and hence acceleration of a proof mass) and excel at high-frequency vibration measurements. Piezoresistive types use strain-sensitive resistors in a bridge and are good for low-frequency and shock measurements. MEMS capacitive accelerometers are also common, but among the given options, “piezoelectric and piezoresistive” is the correct pair. LVDT measures displacement, RTD measures temperature, and “magnetic pickup” is typically a velocity sensor (e.g., for rotating machinery), not a direct acceleration transducer.

Step-by-Step Solution:

Verification / Alternative check:
Instrumentation catalogs categorize accelerometers mainly as piezoelectric, piezoresistive, and MEMS capacitive. Training material for vibration analysis emphasizes piezoelectric devices for broad dynamic ranges and piezoresistive for low-frequency, high-shock environments.

Why Other Options Are Wrong:

• LVDT and piezoelectric: LVDT is not an accelerometer.
• Magnetic pickup and piezoelectric: Magnetic pickup senses velocity/rotation, not acceleration directly.
• RTD and magnetic: Neither is an acceleration sensor.
• LVDT and RTD: Displacement and temperature devices, respectively.

Common Pitfalls:
Equating any motion sensor with accelerometers; overlooking that many systems derive acceleration from position/velocity but that is different from direct acceleration sensing.

Final Answer:
piezoelectric and piezoresistive.