Programming instructions

Chapter 18 Things You Should Know about SCXI
© National Instruments Corporation 18-3 LabVIEW Data Acquisition Basics Manual
Figure 18-1.
Common Types of Transducers/Signals and Signal Conditioning
Amplification
The most common type of signal conditioning is
amplification
. The two
advantages to amplifying electrical signals are that it improves the accuracy
of the resulting digitized signal and that it reduces noise.
For the highest possible accuracy, amplify the signal so the maximum
voltage swing equals the maximum input range of the analog-to-digital
converter (ADC) (otherwise known as a digitizer). Your system should
amplify low-level signals at the DAQ device or at the SCXI module located
nearest to the signal source, as shown in Figure 18-2.
Figure 18-2.
Amplifying Signals near the Source to Increase Signal-to-Noise Ratio
Transducers/Signals
Thermocouples
RTDs
Strain Gauges
Common Mode
or High Voltages
Loads Requiring AC Switching
or Large Current Flow
Signals with High
Frequency Noise
Signal Conditioning
Current Excitation, Four Wire
and Three Wire Configuration,
Linearization
Amplification, Linearization, and
Cold-Junction Compensation
Voltage Excitation Bridge
Configuration, and Linearization
Isolation Amplifiers
(Optical Isolation)
Electromechanical Relays
or Solid-State Relays
Lowpass Filters
DAQ Board
+
-
ADC
DAQ Board
Instrumentaion
Amplifier
MUX
Low-Level Signal
External
Amplifier
Lead Wires
Noise