20 Multiple Choice Questions (MCQs) on Sensors, Thermocouples, RTDs, ADCs

20 Multiple Choice Questions (MCQs) on Sensors, Thermocouples, RTDs, ADCs

What is the primary function of a thermocouple?

(a) produces a change in resistance for a change in temperature
(b) produces a change in voltage for a change in temperature
(c) is made of two dissimilar metals
(d) answers (b) and (c)
Answer: (b) produces a change in voltage for a change in temperature

In a thermocouple circuit where each of the thermocouple wires is connected to a copper circuit board terminal,

(a) an unwanted thermocouple is produced
(b) compensation is required
(c) a reference thermocouple must be used
(d) answers (a), (b), and (c)
(e) answers (a) and (c)
Answer: (a) an unwanted thermocouple is produced

What is the purpose of a thermocouple signal conditioner?

(a) gain
(b) compensation
(c) isolation
(d) common-mode rejection
(e) all of the answers
Answer: (e) all of the answers

How does an RTD respond to temperature changes?

(a) produces a change in resistance for a change in temperature
(b) has a negative temperature coefficient
(c) has a wider temperature range than a thermocouple
(d) all of these
Answer: (a) produces a change in resistance for a change in temperature

What does a 3-wire bridge aim to eliminate in an RTD circuit?

(a) nonlinearity of an RTD
(b) the effects of wire resistance in an RTD circuit
(c) noise from the RTD resistance
(d) none of these
Answer: (b) the effects of wire resistance in an RTD circuit

What is a characteristic of a thermistor?

(a) is less sensitive than an RTD
(b) can measure a greater temperature range than a thermocouple
(c) can be used in a constant-current configuration or a Wheatstone bridge
(d) all of the above
Answer: (c) can be used in a constant-current configuration or a Wheatstone bridge

In what applications are both RTDs and thermistors commonly used?

(a) circuits that measure resistance
(b) circuits that measure temperature
(c) bridge circuits
(d) constant-current-driven circuits
(e) answers (b), (c), and (d)
(f) answers (b) and (c) only
Answer: (b) circuits that measure temperature

What happens to a strain gauge when its length increases?

(a) it produces more voltage
(b) its resistance increases
(c) its resistance decreases
(d) it produces an open circuit
Answer: (b) its resistance increases

What does a higher gauge factor indicate about a strain gauge?

(a) less sensitive to a change in length
(b) more sensitive to a change in length
(c) has more total resistance
(d) made of a physically larger conductor
Answer: (b) more sensitive to a change in length

In many types of pressure transducers, what is commonly used?

(a) thermistors
(b) RTDs
(c) strain gauges
(d) none of these
Answer: (c) strain gauges

Gauge pressure is measured relative to

(a) ambient pressure
(b) a vacuum
(c) a reference pressure
Answer: (c) a reference pressure

How can the flow rate of a liquid be measured?

(a) with a string
(b) with a temperature sensor
(c) with an absolute pressure transducer
(d) with a differential pressure transducer
Answer: (d) with a differential pressure transducer

What does a basic sample-and-hold circuit contain?

(a) an analog switch and an amplifier
(b) an analog switch, a capacitor, and an amplifier
(c) an analog multiplexer and a capacitor
(d) an analog switch, a capacitor, and input and output amplifiers
Answer: (b) an analog switch, a capacitor, and an amplifier

In a sample/track-and-hold circuit,

(a) the voltage at the end of the sample interval is held
(b) the voltage at the beginning of the sample interval is held
(c) the average voltage during the sample interval is held
(d) the output follows the input during the sample interval
(e) answers (a) and (d)
Answer: (e) answers (a) and (d)

What is the aperture time in an analog switch?

(a) fully open after the control switches from hold to sample
(b) fully close after the control switches from sample to hold
(c) fully open after the control switches from sample to hold
(d) fully close after the control switches from hold to sample
Answer: (b) fully close after the control switches from sample to hold

How many discrete values can an 8-bit analog-to-digital converter (ADC) represent?

(a) 144 discrete values of an analog input
(b) 4096 discrete values of an analog input
(c) a continuous set of values of an analog input
(d) 256 discrete values of an analog input
Answer: (b) 4096 discrete values of an analog input

What is the minimum sampling rate for an analog signal?

(a) twice the maximum frequency
(b) twice the minimum frequency
(c) the maximum frequency
(d) the minimum frequency
Answer: (a) twice the maximum frequency

What causes quantization error in an ADC?

(a) poor resolution
(b) nonlinearity of the input
(c) a missing bit in the output
(d) a change in the input voltage during the conversion time
Answer: (d) a change in the input voltage during the conversion time

How can quantization error be avoided in an ADC?

(a) using a higher resolution ADC
(b) using a sample-and-hold prior to the ADC
(c) shortening the conversion time
(d) using a flash ADC
Answer: (b) using a sample-and-hold prior to the ADC

Where is zero-voltage switching commonly used?

(a) determining thermocouple voltage
(b) SCR and triac power-control circuits
(c) balanced bridge circuits
(d) RFI generation
Answer: (b) SCR and triac power-control circuits

What is a major disadvantage of nonzero switching of power to a load?

(a) lack of efficiency
(b) possible damage to the thyristor
(c) RF noise generation
Answer: (c) RF noise generation

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