National Instruments SCB-68 User Manual page 7

Contents
Single-Ended Connection Considerations ...................................................... 3-8
Connecting Analog Output Signals ............................................................................... 3-10
Connecting Digital Signals............................................................................................ 3-11
Connecting Timing Signals ........................................................................................... 3-12
Noise Considerations..................................................................................................... 3-13
Chapter 4
Using Thermocouples
Switch Settings and Temperature Sensor Configuration............................................... 4-2
Special Considerations .................................................................................................. 4-3
Chapter 5
Adding Components for Special Functions
Channel Pad Configurations.......................................................................................... 5-2
Conditioning Analog Input Channels ............................................................. 5-2
Conditioning Analog Output Channels........................................................... 5-3
Conditioning PFI0/TRIG1 .............................................................................. 5-4
Accuracy and Resolution Considerations...................................................................... 5-5
Open Thermocouple Detection...................................................................................... 5-5
Differential Open Thermocouple Detection ................................................... 5-6
Single-Ended Open Thermocouple Detection ................................................ 5-6
Sources of Error .............................................................................................. 5-6
Lowpass Filtering .......................................................................................................... 5-7
Theory of Operation........................................................................................ 5-7
One-Pole Lowpass RC Filter .......................................................................... 5-10
Selecting Components..................................................................................... 5-11
Adding Components ....................................................................................... 5-11
Lowpass Filtering Applications ...................................................................... 5-13
Special Consideration for Analog Input Channels.......................................... 5-14
Special Consideration for Analog Output Signals .......................................... 5-14
Special Consideration for Digital Trigger Input Signals ................................ 5-15
Measuring a 4 to 20 mA Current................................................................................... 5-16
Theory of Operation........................................................................................ 5-16
SCB-68 Shielded Connector Block User Manual
Single-Ended Connections for Floating Signal Sources
(RSE Input Mode).......................................................................... 3-9
Single-Ended Connections for Grounded Signal Sources
(NRSE Input Mode)....................................................................... 3-9
Single-Ended Lowpass Filter............................................................ 5-12
Differential Lowpass Filter............................................................... 5-12
Analog Output and Digital Input Lowpass Filtering ........................ 5-12
Noise Filtering .................................................................................. 5-13
Antialiasing Filtering ........................................................................ 5-13
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