National Instruments DAQCard-1200 Analog Input Circuitry

Chapter 4 Theory of Operation

DAQCard-1200 User Manual 4-6 © National Instruments Corporation

Figure 4-4. Analog Input Circuitry

Analog Input Circuitry

The analog input circuitry consists of two analog input multiplexers, mux

counter/gain select circuitry, a software-programmable gain amplifier, a

12-bit ADC, and a 12-bit FIFO memory that is sign-extended to 16 bits.

The two input multiplexers route the input channels to the instrumentation

amplifier in either RSE, NRSE, or DIFF mode. The input multiplexers

provide input overvoltage protection of ±35 V powered on and ±25V

powered off.

The mux counters control the input multiplexers. The DAQCard-1200

can perform either sing le-ch annel data acquisition or multiple-channel

(scanned) data acquisition. These two modes are software selectable.

Forsingle-channel data acquisition, you select the channel and gain before

initiating data acquisition. These gain and multiplexer settings remain

constant during the entire data acquisition process. For multiple-channel

data acquisition, you select the highest numbered channel and gain before

data acquisition is initiated. Then the mux counter decrements from the

highest numbered channel to channel 0 and repeats the process. Thus you

Sample-

and-Hold

Amp

DAQ

Timing

Gain Select/

Mux Counter

Mux

Pro-

grammable

Gain Amp

12-Bit

ADC

1k

Sample

A/D

FIFO

External Trigger Counter/Timer

Signals

WRT/RD

CON

V

EXTCONV*

OUTB1

EXTTRIG

ACH0

ACH1

ACH2

ACH3

ACH4

ACH5

ACH6

ACH7

12 12

8

6

A/D

Data Data

Data

I/O Connector

GAIN0

GAIN1

GAIN2

Convert

AISENSE/

AIGND

PCMCIA I/O Channel

8

Data

External Convert

Output B1

PCMCIA Interface Decode Circuitry

Dither

Circuitry Dither Enable

Dither

Contents

Main Page Important Information Warranty Copyright Trademarks WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS Contents Chapter 4 Theory of Operation Page Tables About This Manual Organization of This Manual Conventions Used in This Manual National Instruments Documentation Related Documentation Introduction About the DAQCard-1200 What You Need to Get Started Software Programming Choices LabVIEW and LabWindows/CVI Application Software NI-DAQ Driver Software Register-Level Programming Optional Equipment Unpacking Installation and Configuration Installation Configuration Analog Input Configuration Analog Input Polarity Analog Input Mode RSE Input (Eight Channels, Default Setting) NRSE Input (Eight Channels) DIFF Input (Four Channels) Analog Output Configuration Analog Output Polarity Digital I/O Configuration Counter Configuration Signal Connections I/O Connector Figure 3-1. DAQCard-1200 I/O Connector Pin Assignments Signal Connection Descriptions Analog Input Signal Connections + Types of Signal Sources Floating Signal Sources Ground-Referenced Signal Sources Input Configurations Differential Connection Considerations (DIFF Configuration) Differential Connections for Grounded Signal Sources Figure 3-3. Differential Input Connections for Grounded Signal Sources Differential Connections for Floating Signal Sources Figure 3-4. Differential Input Connections for Floating Sources Single-Ended Connection Considerations Single-Ended Connections for Floating Signal Sources (RSE Configuration) Single-Ended Connections for Grounded Signal Sources (NRSE Configuration) Common-Mode Signal Rejection Considerations Analog Output Signal Connections Digital I/O Signal Connections Page Port C Pin Connections Timing Specifications Mode 1 Input Timing Mode 1 Output Timing Mode 2 Bidirectional Timing Page DAQ and General-Purpose Timing Signal Connections DAQ Timing Connections Page Page Page General-Purpose Timing Signal Connections Page Page Figure 3-18. Frequency Measurement Application Chapter 3 Signal Connections DAQCard-1200 User Manual 3-30 National Instruments Corporation Figure 3-19. General-Purpose Timing Signals The GATE and OUT signals in Figure3-19 are referenced to the rising edge of the CLK signal. Power Connections National Instruments Corporation 4-1 DAQCard-1200 User Manual Theory of Operation This chapter explains the operation of each functional unit of the DAQCard-1200. Figure 4-1. DAQCard-1200 Block Diagram Functional Overview The block diagram in Figure 4-1 shows a functional overview of the DAQCard-1200. PC Card I/O Channel Interface Circuitry Timing Chapter 4 Theory of Operation Figure 4-3. Timing Circuitry DAQCard-1200 User Manual 4-4 National Instruments Corporation Analog Input Analog Input Circuitry Page Data Acquisition Timing Data Acquisition Operation Continuous Data Acquisition Interval Data Acquisition Data Acquisition Rates Page Analog Output Analog Output Circuitry Power-On State DAC Timing Digital I/O Calibration Calibration at Higher Gains Calibration Equipment Requirements Using the Calibration Function Page A Specifications Analog Input Input Characteristics Transfer Characteristics Amplifier Characteristics Dynamic Characteristics Stability Analog Output Output Characteristics Transfer Characteristics Page Timing I/O Digital Trigger Bus Interface Power Requirement Physical Page B Differences among the Lab-PC+, the DAQPad-1200, and the DAQCard-1200 Page C Power-Management Modes Page D PC Card Questions and Answers Configuration Operation Resources Page Page E Technical Support Resources NI Web Support Online Problem-Solving and Diagnostic Resources Software-Related Resources Worldwide Support Glossary Numbers/Symbols A B C D E F G Page Page V Index Numbers A B C D E F G I L M N O R S T U V W