This document provides an overview of data acquisition concepts including transducers, signals, signal conditioning, and DAQ hardware. It discusses how transducers convert physical phenomena into measurable signals, the differences between analog and digital signals, and common signal conditioning techniques like amplification. It also describes common components of DAQ devices, and considerations for configuring devices like resolution, range, gain, and code width to optimize measurement precision.

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CHAPTER 1
Transducers, Signals, and Signal Conditioning
Topics
• Data Acquisition Overview
• Transducers
• Signals
• Signal Conditioning
Lesson 8
Data Acquisition and Waveforms

2. System Overview

3. Transducer Overview
Topics
• What is a Transducer?
• Types of Transducers

4. What is a Transducer?
A transducer converts a physical
phenomena into a measurable signal
Signal
Physical
Phenomena

5. Signal Overview
Topics
• Types of Signals
• Information in a Signal
– State, Rate, Level,
Shape, and Frequency

6. Signal Classification
Your Signal
AnalogDigital

7. Two possible levels:
• High/On (2 - 5 Volts)
• Low/Off (0 - 0.8 Volts)
Two types of information:
• State
• Rate
Digital Signals
Digital
Your Signal

8. Digital Signal Information
Digital
Your Signal

9. Analog Signals
Your Signal
Analog
Continuous signal
• Can be at any value with
respect to time
Three types of information:
• Level
• Shape
• Frequency (Analysis required)

10. Analog Signal Information
Your Signal
Analog
Analysis
Required

11. Signal Conditioning Overview
Topics
• Purpose of Signal Conditioning
• Types of Signal Conditioning

12. Why Use Signal Conditioning?
• Signal Conditioning takes a signal that is difficult
for your DAQ device to measure and makes it
easier to measure
• Signal Conditioning is not always required
– Depends on the signal being measured
Noisy, Low-Level Signal Filtered, Amplified Signal

13. Amplification
• Used on low-level signals (i.e. thermocouples)
• Maximizes use of Analog-to-Digital Converter (ADC) range
and increases accuracy
• Increases Signal to Noise Ratio (SNR)
Low-Level Signal External
Amplifier
DAQ Device
Lead Wires
Instrumentation
Amplifier
Noise
ADC
+
_

14. DAQ Hardware Overview
Topics
• Types of DAQ Hardware
• Components of a DAQ device
• Configuration Considerations

15. Data Acquisition Hardware
DAQ Hardware turns your PC into a
measurement and automation system
Computer
Your Signal
DAQ Device
Terminal Block
Cable

16. DAQ Device
Computer
DAQ Device
• Most DAQ devices have:
– Analog Input
– Analog Output
– Digital I/O
– Counters
• Specialty devices exist for specific applications
– High speed digital I/O
– High speed waveform generation
– Dynamic Signal Acquisition (vibration, sonar)
• Connect to the bus of your computer

17. Configuration Considerations
• Analog Input
– Resolution
– Range
– Gain
– Code Width
– Mode (Differential, RSE, or NRSE)
• Analog Output
– Internal vs. External Reference Voltage

18. Resolution
• Number of bits the ADC uses to represent a signal
• Resolution determines how many different voltage
changes can be measured
• Example: 12-bit resolution
• Larger resolution = more precise representation of your
signal
# of levels = 2resolution = 212 = 4,096 levels

19. Range
• Minimum and maximum voltages the ADC can digitize
• DAQ devices often have different available ranges
– 0 to +10 volts
– -10 to +10 volts
• Pick a range that your signal fits in
• Smaller range = more precise representation of your signal
– Allows you to use all of your available resolution

20. Gain
• Gain setting amplifies the signal for best fit
in ADC range
• Gain settings are 0.5, 1, 2, 5, 10, 20, 50, or
100 for most devices
• You don’t choose the gain directly
– Choose the input limits of your signal in LabVIEW
– Maximum gain possible is selected
– Maximum gain possible depends on the limits of
your signal and the chosen range of your ADC
• Proper gain = more precise representation
of your signal
– Allows you to use all of your available resolution

21. Gain Example
100 200150500
Time (ms)
0
1.25
5.00
2.50
3.75
6.25
7.50
8.75
10.00
Amplitude
(volts)
Different Gains for 16-bit Resolution
(5kHz Sine Wave)
Gain = 2
| ||||
Your Signal
Gain = 1
– Input limits of the signal = 0 to 5 Volts
– Range Setting for the ADC = 0 to 10 Volts
– Gain Setting applied by Instrumentation Amplifier = 2

22. • Code Width is the smallest change in the signal your
system can detect (determined by resolution, range, and
gain)
• Smaller Code Width = more precise representation of your
signal
• Example: 12-bit device, range = 0 to 10V, gain = 1
code width =
range
gain * 2 resolution
10
1 * 212
= 2.4 mV
range
gain * 2 resolution
=
20
1 * 212
= 4.8 mVIncrease range:
10
100 * 212
= 24 mVIncrease gain:
Code Width