Signal conditioning, generation and acquisition

Question 1

INTERFACING DIGITAL SYSTEMS WITH ANALOGUE WORLD-WHAT ARE THESE SYSTEMS ?

Answer 1

Signal conditioning
Common circuits with operational amplifiers
filters

Question 2

What is signal conditioning ?

Answer 2

Crucial step in the design of a mechatronic system.

GOALS:
-protection (prevents damage from high current or voltage)
-conversion (allows signal to be analysed)
-level (adapts the level of output to the input levels)
-noise reduction (eliminate spurious signals)
-manipulation (makes signal easier to understand)

Question 3

SIGNAL CONDITIONING - What is protection

Answer 3

Protection: ZENER DIODE. Break down when voltage goes above the set limit. Its resistance drops and so as the voltage.

Protection: Optoisolator
Is used to isolate circuits and protect hardware from damage.

It converts the electrical signal into an optical signal. And then detected by an Output

Question 4

What are operational amplifiers ?

Answer 4

Basis of many signal conditioning modules is the operational amplifier. They can perform mathematical operations when equipped right (with comparator, inverting amplifier, etc..)

Question 5

Operational amplifiers-What is a comparator?

Answer 5

Detects when difference between two signals is positive or negative

Question 6

Operational amplifiers-What is an inverting amplifier ?

Answer 6

Often, need to amplify/attenuate a signal to make it compatible with data acquisition system.

Question 7

Operational amplifiers-What is a non inverting amplifier ?

Answer 7

only to amplify signal

Question 8

Operational amplifiers-What is a summing amplifier?

Answer 8

Sum two or more signal

Question 9

WHAT IS A FILTER ?

Answer 9

Signals filtered before being elaborated.
Low-pass filters (removal of high frequency noise), are the most common filters

Question 10

CONVERSION : A/D AND D/A; How an analogue signal is converted ?

Answer 10

Through different units. The continuous analogue signal goes through sample and hold and converter, to become digital. Discretised in time and in magnitude. = called A/D acquisition.

Question 11

What are the main types of A/D converters?

Answer 11

• successive approximations
  -flash ramp
  -dual ramp
  voltage to frequency

Question 12

A/D CONVERTERS - what are ramp converters?

Answer 12

slow method. Generated input and rise. Compared with analogue input.

Question 13

A/D CONVERTERS - what IS SUCCESSIVE APPROXIMATION ?

Answer 13

Add successive lesser significant bits for which total does not exceed analogue value.

example : convert 5v input

xxxx (initial conversion value unknown)

protocol :
1. test most significant bit
2. compare with 15V/2 (7.5V)
3. if measured voltage greater than comparator, set 1, else =0
4. 5>7.5= FALSE => 0xxx

etc…