Question

An A.C signal conditioning system is normally used for

• A. Resistive transducer like strain gauges
• B. Inductive and capacitive transducer
• C. Piezoelectric transducer
• D. Voltage transducer

Hint:

Signal Conditioning. AC signal conditioning (e.g., using carrier frequencies, AC bridges, phase detection) is often necessary for transducers whose output is a change in inductance or capacitance (impedance-based sensors). DC conditioning is typical for resistive sensors.

Answer 1

The Correct Option is B

Signal conditioning adapts the output signal from a transducer into a form suitable for the next stage (e
g
, display, recording, processing)
Transducers can be active (self-generating, like piezoelectric) or passive (requiring external excitation)
Passive transducers can change resistance, inductance, or capacitance in response to the measurand
- Resistive transducers (like strain gauges, RTDs, thermistors) typically change resistance, which can be measured using DC or AC circuits (like Wheatstone bridge), but dedicated AC conditioning isn't usually mandatory
- Inductive transducers (like LVDT, variable reluctance sensors) and capacitive transducers rely on changes in inductance or capacitance
Measuring these changes often requires an AC excitation signal, as the impedance (\(X_L = \omega L\), \(X_C = 1/(\omega C)\)) is frequency-dependent
AC signal conditioning systems (using AC bridges, carrier amplifiers, phase-sensitive detectors) are specifically designed to work with the AC output signals generated by or required for these types of transducers
- Piezoelectric transducers generate a charge or voltage directly in response to pressure/force (active transducer), usually requiring charge amplifiers or high-impedance voltage amplifiers, not typically AC conditioning in the same sense
- Voltage transducers directly output a voltage signal
Therefore, AC signal conditioning systems are most commonly associated with inductive and capacitive transducers whose operation relies on AC impedance characteristics