Digital Systems: Resolution and Frequency Response

Questions and Answers

What does the term 'sensitivity' of a sensor indicate?

The minimum measurable value of the sensor

The change in output for a given change in input (correct)

The maximum output a sensor can produce

The time taken for the sensor to respond

What is defined as the minimum increment in stimulus that causes a measurable change in output?

Sensitivity

Resolution (correct)

Response Time

Transfer Function

Which mathematical representation is often associated with the concept of sensitivity in sensors?

$d aT + b = 1$

$dR = a \, ext{Ω}$

$R = b + rac{dR}{dT}$

$dR = a \, dT$ (correct)

What is the primary purpose of calibration methods for sensors?

To ensure the accuracy of sensor measurements Signup and view all the answers

Which concept is closely related to how a sensor reacts over a range of frequencies?

Bandwidth Signup and view all the answers

What does resolution indicate in a digital system?

The smallest change detectable by the system. Signup and view all the answers

Which term describes the ability of the device to respond to a harmonic input?

Frequency response Signup and view all the answers

What is typically measured by the response time of a device?

Time required to reach steady state after a change in input. Signup and view all the answers

What does calibration determine in a sensor or actuator?

The transfer function of the device. Signup and view all the answers

Which design parameter indicates the narrow range of frequencies over which the device effectively operates?

Flat frequency range Signup and view all the answers

What represents the phenomenon of a device stabilizing its output after a change in input?

Response time Signup and view all the answers

Which of the following best characterizes cutoff frequencies?

The frequencies at which output begins to significantly decrease. Signup and view all the answers

Which response time is typically more desirable in devices?

Fast response time Signup and view all the answers

Which method is commonly used to establish nonlinearity of a sensor?

Using the calibration curve to draw a best fit line Signup and view all the answers

What does deadband refer to in a device's response to input?

The range over which the device shows no change in output Signup and view all the answers

Why is output impedance significant in sensor interfacing?

It defines the relationship between output voltage and current Signup and view all the answers

Which keyword describes the stability of a sensor to produce consistent readings under identical conditions?

Repeatability Signup and view all the answers

What does the term 'transfer function' refer to in the context of sensors?

A graph mapping input to corresponding output values Signup and view all the answers

Which aspect is NOT directly related to a sensor's calibration?

Output impedance Signup and view all the answers

How is reliability defined in the context of sensor performance?

As a measure of a device's statistical probability of failure over time Signup and view all the answers

Which factor can influence the frequency response of a sensor?

Sensor's output impedance Signup and view all the answers

Study Notes

Resolution

Defined as 1/2^N, where N is the number of bits in a digital system.
Represents the minimum increment of stimulus detectable by the sensor.

Frequency Response

The ability of a device to respond to sinusoidal inputs.
Plots magnitude as a function of frequency, highlighting usable stimulus ranges for sensors and actuators.
Important design parameters include:
- Bandwidth (B-A, in Hz)
- Flat frequency range (D-C, in Hz)
- Cutoff frequencies (points A and B, in Hz)
- Resonant frequencies

Frequency Response Examples

Bandwidth ranges from 70 Hz to 16.5 kHz, totaling 16.43 kHz.
Flat frequency range extends from 10 kHz to 120 Hz, with a span of 9880 Hz.
Cutoff frequencies identified at 70 Hz and 16.5 kHz.
Resonance occurs at a frequency of 12 kHz.

Response Time

Indicates the duration required for output to reach steady state after input changes.
Typically assessed as the time to reach 90% of the steady state output.
Influenced by both mechanical and electrical inertia of the device.
Fast response times are preferred, while slow times may result in averaged readings.

Calibration

Entails experimental determination of a sensor's transfer function.
Often necessary when transfer function is unknown or operation requires tighter tolerances.
Typically expressed in hours/years or Mean Time Between Failures (MTBF).
Manufacturer usually provides calibration based on accelerated lifetime testing.

Sensitivity

Defined as the change in output corresponding to a unit change in input.
Represents the slope of the transfer function.
Can indicate sensitivity to other environmental factors, such as temperature changes affecting resistance measurement.

Deadband

Characterized by a lack of response within a specific input range where output remains constant.
Indicates insensitivity that should not induce operation unless acceptable.

Output Impedance

Defined as the ratio of output voltage to short-circuit current at the output port.
Essential for interfacing devices; for example, a 500 Ω sensor's output impedance may interface differently with processors depending on their input impedance.

Repeatability

Also known as reproducibility; denotes the sensor's ability to provide the same output under identical conditions over time.
Expressed as a percentage of the input full scale, measuring the maximum difference between readings taken at different times.

Reliability

Statistical measure indicating the quality of a device's operational capability under normal conditions.
Reflects performance without failure over a specified time or number of cycles.

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Description

Explore key concepts related to resolution in digital systems and the frequency response of devices. Understand how resolution is defined and its significance, along with the importance of frequency response in device usability. This quiz covers both theoretical aspects and practical implications for design.