Question

A piezoelectric transducer with sensitivity of 30 mV/kPa is intended to be used in the range of 0 kPa to 100 kPa. The readout circuit has a peak noise amplitude of 0.3 mV and measured signals over the full pressure range are encoded with 10 bits. The smallest pressure that produces a non-zero output, in units of Pa, is approximately
1. 10
2. 100
3. 240
4. 300

Answer 1

Correct Answer - Option 2 : 100

Given that,

Sensitivity = 30 mV/kPa

Range = 0 kPa to 100 kPa

Full scale voltage = 30 × 10^-3 × 100 = 3 V

Noise of readout circuit = 0.3 mV

V_ref = 3.0003V

Number of bits = n = 10

\(Resolution = \frac{{{V_{ref}}}}{{{2^n} - 1}} = \frac{{3.0003}}{{{2^{10}} - 1}} = 2.933 \times {10^{ - 3}}V\)

= 0.00293V

Smallest readout = 0.00293V.

Resolution at input side \(= \frac{{0.00293}}{{30 \times {{10}^{ - 3}}}} = 97.66pa\)

≈ 100 pa