Measurement and Instrumentation Flashcards

Which type of ADC offers the fastest conversion speed?

Answer: Flash (parallel) ADC

A flash ADC uses 2ⁿ−1 comparators simultaneously to determine all bits at once, making it the fastest but most hardware-intensive ADC type.

In a digital multimeter (DMM), the term '4½ digit display' means the meter can show:

Answer: Up to 19999 counts

A 4½ digit display has four full digits (0–9) and one half-digit that can only display 0 or 1, giving a maximum reading of 19999.

The primary purpose of a shunt resistor in an ammeter is to:

Answer: Bypass excess current around the galvanometer movement

A low-resistance shunt in parallel with the galvanometer carries most of the current, extending the ammeter's range while keeping the movement current small.

Which phenomenon causes the zero-shift error in a strain gauge measurement when temperature changes?

Answer: Thermal expansion mismatch between the gauge and substrate

Differential thermal expansion between the metallic gauge element and its bonded substrate generates a spurious apparent strain signal with temperature.

In frequency measurement using a CRO, if the time period of one complete cycle is 4 ms, the frequency is:

Answer: 250 Hz

Frequency = 1/T = 1/0.004 s = 250 Hz.

A resistance temperature detector (RTD) uses which property to sense temperature?

Answer: Predictable change in electrical resistance with temperature

RTDs (e.g., PT100) exploit the nearly linear increase in metal resistance with temperature, offering high accuracy and stability.

The resolution of a 12-bit DAC with a full-scale output of 5 V is approximately:

Answer: 1.22 mV

Resolution = Full-scale / (2ⁿ − 1) = 5 V / 4095 ≈ 1.22 mV, representing the smallest output voltage step.