Mechatronics Exam 1 Study Notes

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are the elements of a measurement system?

a sensor, 2. a signal conditioner, 3. a display system

What is a sensor?

A sensor produces a signal related to the quantity being measured.

What components are typically included in a signal conditioner?

A signal conditioner is a device that modifies raw sensor signals into a form that can be used for data acquisition and machine control.

What are the differences between an open and closed loop system, and what are their advantages?

Open loop - input does not depend on an output (advantage is that it is low cost and simple). Closed loop - output compared to input (offer superior accuracy and adaptability by incorporating feedback). Signup and view all the answers

List the sensor performance terminology discussed.

<ol> <li>Range and span, 2. Error, 3. Accuracy, 4. Sensitivity, 5. Hysteresis error, 6. Non-linearity error, 7. Repeatability, 8. Stability, 9. Dead Band/ time, 10. Resolution, 11. Output impedance</li> </ol> Signup and view all the answers

What physical properties can be measured by sensors?

Displacement, Position, Proximity, acceleration force, force, fluid pressure, liquid flow, liquid level, temperature, light Signup and view all the answers

Describe how a potentiometer sensor works.

Measures the distance or displacement of an object in a linear or rotary motion and converts it into an electrical signal Signup and view all the answers

Explain how a strain-gauged element functions as a sensor.

It is a sensor whose resistance varies with applied force; it converts forces, pressure, tension, weight, etc. into an electrical change in electrical resistance which can then be measured. Signup and view all the answers

What is a capacitive element?

An electrical component that stores electrical charge and responds to changes in voltage and current. Signup and view all the answers

What is a differential transformer used for?

Converts linear motion (displacement) of an object into an electrical signal. Signup and view all the answers

Explain how eddy current proximity sensors work.

If there is a metal object in close proximity to this alternating magnetic field, then eddy currents are induced in it. Signup and view all the answers

Describe the operating principle of an inductive proximity switch.

This consists of a coil wound round a core. When the end of the coil is close to a metal object its inductance changes. Signup and view all the answers

What is the function of optical encoders?

A device that converts motion into a sequence of digital pulses. Signup and view all the answers

How do absolute encoders determine position?

Gives the actual position using binary numbers. Signup and view all the answers

What is the typical measurement range for pneumatic sensors?

Such sensors are used for the measurement of displacements of fractions of mm in ranges which typically are about 3 to 12 mm. Signup and view all the answers

What type of action does a Microswitch require to close its contacts?

It is a small electrical switch which requires physical contact and a small operating force to close the contacts. Signup and view all the answers

Describe a common application for a Reed switch.

Such a switch is very widely used for checking the closure of doors. It is also used with such devices as tachometers (counting turns). Signup and view all the answers

How do photosensitive devices detect proximity?

Can be used to detect the presence of an opaque object by its breaking a beam of light, or infrared radiation, falling on such a device or by detecting the light reflected back by the object. Signup and view all the answers

What is measured by Hall effect sensors?

A device to measure the magnitude of a magnetic field as voltage change. Signup and view all the answers

How does a tachogenerator operate?

Operates on a generator principle where the induced voltage is proportional to the speed of rotation. Signup and view all the answers

Explain how a strain gauge load cell measures force.

Used form of force-measuring transducer is based on the use of electrical resistance strain gauges to monitor the strain produced in some member when stretched, compressed or bent by the application of the force. Signup and view all the answers

What quantities are piezoelectric sensors suitable for measuring?

Used for the measurement of pressure, force and acceleration. Signup and view all the answers

What does a tactile sensor measure?

Measuring device that indicates physical contact between two objects. Signup and view all the answers

List mechanical and electrical methods of measuring fluid pressure.

Mechanical: U-tube manometer, Bourdon tube, Diaphragm and Bellows. Electrical: Strain Gauge, Capacitive sensor, Potentiometric, Resonant Wire, Piezoelectric, Magnetic, Optical. Signup and view all the answers

Name some devices that are used for measuring temperature.

-Bimetallic strips, -Resistance temperature detectors (RTDs), -Thermistors, -Thermodiodes and transistors, -Thermocouples Signup and view all the answers

Why is signal conditioning necessary?

<ol> <li>Protection (to prevent damage to the next element), fuses, diodes. 2. Getting the signal into the right type of signal, like resistance change to voltage change. 3. Getting the level of the signal right, the signal might be just a few millivolts (Arduino reads 5mV as the smallest value). 4. Eliminating or reducing noise, by adding filters. 5. Signal manipulation, using pulses to get a constant value (to overcome drift)</li> </ol> Signup and view all the answers

What is the difference between passive and active filters?

Passive filters: use only resistors, capacitors and inductors. Active filters: use operational amplifiers. Signup and view all the answers

Why are Op-Amp circuits used?

We can think of it as a circuit element that is very useful for signal manipulation. signals go in, circuit stuff happens (that we do not design), the external power supply provides the electrical power to produce the output Signup and view all the answers

What are the ideal electrical impedance conditions for measuring and for maximizing power transfer?

Measuring: we do not want any power transfer: Rmeas >> Rsensor. Maximizing power transfer: impedance matching: Rsource = Rload Signup and view all the answers

When would a Wheatstone bridge circuit be used?

We would use one when dealing with a strain gauge. Signup and view all the answers

How are analog signals sampled for ADC?

Convert a digital representation of potential values to analog (via a DAC) and compare with the analog signal to determine the smallest digital value for which the analog signal is greater (uses binary numbers) Signup and view all the answers

What is the function of actuation systems?

Actuation systems are the elements of control systems which are responsible for transforming the output of a microprocessor or control system into a controlling action on a machine or device Signup and view all the answers

Describe pneumatic systems.

A system in which a gas, such as air, transmits a force exerted on the gas in an enclosed space. Signup and view all the answers

Describe hydraulic systems.

Uses liquid (oil), Fluid transfers force to mechanical components. Signup and view all the answers

What is the function of valves in hydraulic and pneumatic systems?

Are used with hydraulic and pneumatic systems to direct and regulate the fluid flow. Signup and view all the answers

Describe linear actuators, also known as cylinders.

Cylindrical tube along which a piston/ram can slide. There are two basic types, single-acting cylinders (an internal spring returns the piston) and double-acting cylinders. Signup and view all the answers

What are the purposes/uses for basic mechanisms?

<ol> <li>force amplification, e.g. that given by levers; 2. change of speed/torque, e.g. that given by gears; 3. transfer of rotation about one axis to rotation about another, e.g. a timing belt; 4. particular types of motion, e.g. that given by a quick-return mechanism (time for return stroke less than forward stroke)</li> </ol> Signup and view all the answers

Flashcards

What is a sensor?

A sensor produces a signal related to the quantity being measured.

Signal conditioner?

Signal conditioner modifies raw sensor signals for data acquisition and machine control.

Open vs. Closed Loop?

Open loop: input independent of output (simple, low cost). Closed loop: output compared to input (accurate, adaptable).

Sensor performance terms?

Range & span, error, accuracy, sensitivity, hysteresis, non-linearity, repeatability, stability, dead band/time, resolution, output impedance.