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National Instruments Corporation
4-1
4
Theory of Operation
This chapter contains a functional overview of the SCXI-1112 module and
explains the operation of each functional unit making up the SCXI-1112
module.
Functional Overview
The block diagram in Figure 4-1 illustrates the key functional components
of the SCXI-1112 module.
Figure 4-1.
SCXI-1112 Module Block Diagram
Lowpass
Filter
Open TC
Detect
Digital
Control
Calibration EEPROM
MCH0+
FIFO
Autozero
Control
Switch
Control
SCXI Signal Connector
Rear Signal Connector
Switch
MCH0–
Switch
Inst.
Amp
+
Buffer
Switch
Switch
Switch
8 to 1 Mux
Buffer
AB0+
AB0–
–
Input Protection
Thermocouple Inputs
Open TC Indicators
Cold Junction Sensors
(1 per Channel)
Autozero Calibration
Switches
Autozero Calibration
Switches
Lowpass
Filter
Open TC
Detect
Inst.
Amp
+
Buffer
–
Input Protection
Drivers
8 to 1 Mux
Thermistor
Excitation
SCXIbus
Interface