Block 1- lecture 2

Question 1

Common ways to transmit information?

Answer 1

• electric current

- pneumatic pressures

Question 2

Advantage of current as a signal?

Answer 2

-nearly independent of resistance

Question 3

Error?

Answer 3

difference between measured value and desired value

Question 4

Block definitions?

Answer 4

way of showing a system with inputs and outputs

Question 5

Transfer function?

Answer 5

relationship between input and output

Question 6

Accuracy?

Answer 6

maximum overall error of a device/system

Question 7

Sensitivity?

Answer 7

change of output for change in input

Question 8

Hysteresis and reproducibility?

Answer 8

how much values change for repeated trials

Question 9

Resolution?

Answer 9

minimum measurable value of input

Question 10

Linearity?

Answer 10

output directly proportional to input

Question 11

static transfer function?

Answer 11

how output relates to input

Question 12

other name for dynamic transfer function?

Answer 12

time response

Question 13

Types of sensor time responses?

Answer 13

first-order and second-order

Question 14

First-order sensor time response?

Answer 14

an exponential time response to step change of input

Question 15

Second-order sensor time response?

Answer 15

combination of exponential and sinusoidal functions

Question 16

Maximum error?

Answer 16

maximum deviation from setpoint

Question 17

settling time?

Answer 17

time (start to finish) that value was out of the allowed deviation

Question 18

Residual error?

Answer 18

deviation from set point as time tends to infinity

Question 19

Types of signal conditioning?

Answer 19

• signal level (amplitude) and bias (zero level)
• linearisation
• conversion
• filtering
• concept of loading

Question 20

Concept of loading?

Answer 20

when a current is drawn from the output of an amplifier

Question 21

Equation for loading on a sensor to find its output voltage?

Answer 21

sensor voltage minus the voltage drop of internal resistance

Question 22

Calculating amplifier output voltage when a circuit draws current?

Answer 22

The output resistance of the amplifier causes a voltage drop

Question 23

Why use a Wheatstone bridge?

Answer 23

To measure resistance variations more precisely

Question 24

How to avoid lead resistance errors in a wheatstone bridge?

Answer 24

use 3 lead wires, to add the lead resistance to both sides of the bridge

Question 25

why use ac for a wheatstone bridge?

Answer 25

so ac interference can be filtered out

Question 26

problems with ac for a wheatstone bridge?

Answer 26

If the sensor has capacitance or inductance,, you’ll need a tunable capacitor on the other side

Question 27

how does ac wheatstone calculation compare to dc?

Answer 27

uses impedance, not resistance