National Instruments SCXI-1503 Figure 4-1. Block Diagram of SCXI-1503

Chapter 4 Theory of Operation

SCXI-1503 User Manual 4-2 ni.com

Figure 4-1. Block Diagram of SCXI-1503

AI 15 +

AI 15 –

Calibration

Source

SCXIbus

Interface

CJSENSOR

Front Signal Connector

Rear Signal Connector

32-to-1 Mux

Input Protection

and Lowpass Filter

Switch

Switch Mux

Inst.

Amp

+

–

AI 0 +

AI 0 –

AI 0 +

AI 0 –

Lowpass

Filter Buffer Buffer

Inst.

Amp

+

–

Gain 31

Gain 0

Lowpass

Filter

Gain Select

Digital Interface

and Control

Buffer

Mux

Calibration EEPROM

Input Select

OUT REF

AI GND

AB 0 +

AB 0 –

SCXIbus Connector

100 µA

IEX 15 –

IEX 15 +

100 µA

IEX 0 –

IEX 0 +

Contents

Main Page Important Information Warranty Copyright Trademarks Patents Conventions Contents Chapter 1 About the SCXI-1503 Chapter 2 Connecting Signals Chapter 3 Configuring and Testing Chapter 4 Theory of Operation Chapter 5 Using the SCXI-1503 Page Tables About the SCXI-1503 What You Need to Get Started National Instruments Documentation Page Installing Application Software, NI-DAQ, and the E/M Series DAQ Device Installing the SCXI-1503 Module into the SCXI Chassis Installing the Terminal Block Configuring the SCXI System Software Page Connecting Signals Analog Input Signal Connections Ground-Referencing the Signals Connecting Resistive Devices to the SCXI-1503 4-Wire Configuration 2-Wire Configuration 3-Wire Resistive Sensor Configuration Lead-Resistance Compensation Using a 3-Wire Resistive Sensor and Two Matched Current Sources Figure 2-4. 3-Wire Configuration Using Matched Current Sources Front Connector Table 2-1. Front Signal Pin Assignments Page Rear Signal Connector Table 2-3 shows the SCXI-1503 module rear signal connector pin assignments. Table 2-3. Rear Signal Pin Assignments Rear Signal Connector Descriptions Page Configuring and Testing SCXI-1503 Software-Configurable Settings Common Software-Configurable Settings Gain/Input Range Input Coupling Configurable Settings in MAX NI-DAQmx Creating a Global Channel or Task Verifying the Signal Verifying the Signal in NI-DAQmx Using a Task or Global Channel Page Page Chapter 4 Theory of Operation Figure 4-1. Block Diagram of SCXI-1503 SCXI-1503 User Manual 4-2 ni.com Front Signal Connector Rear Signal Connector + Rear Signal Connector, SCXIbus Connector, and SCXIbus Interface Digital Control Circuitry Analog Circuitry Analog Input Channels Operation of the Current Sources Theory of Multiplexed Operation Measuring Temperature with Resistive Transducers RTDs RTD Measurement Errors The Relationship Between Resistance and Temperature in RTDs Page Page Page Thermistors Thermistor Measurement Circuits Resistance/Temperature Characteristic of Thermistors Page Using the SCXI-1503 Developing Your Application in NI-DAQmx Typical Program Flowchart Figure 5-1. Typical Program Flowchart for Voltage Measurement Channels General Discussion of Typical Flowchart Creating a Task Using DAQ Assistant or Programmatically Adjusting Timing and Triggering Configuring Channel Properties Page Page Acquiring, Analyzing, and Presenting Completing the Application Developing an Application Using LabVIEW Page Using a NI-DAQmx Channel Property Node in LabVIEW Specifying Channel Strings in NI-DAQmx Text Based ADEs LabWindows/CVI Measurement Studio (Visual Basic 6, .NET, and C#) Programmable NI-DAQmx Properties Calibration Internal/Self-Calibration External Calibration Page A Specifications Analog Input Input Characteristics Transfer Characteristics RTD Measurement Accuracy Amplifier Characteristics Dynamic Characteristics Filter Stability Excitation Power Requirements From SCXI Backplane Environmental Physical Maximum Working Voltage Safety Electromagnetic Compatibility CE Compliance Waste Electrical and Electronic Equipment (WEEE) B Removing the SCXI-1503 Removing the SCXI-1503 from MAX Removing the SCXI-1503 from a Chassis Figure B-1. Removing the SCXI-1503 C Common Questions Page Page Glossary Numbers/Symbols A B C D E G I J L M N O P R S T U V W Index Numerics A C D E F G I O P Q R S T V