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This version is outdated by a newer approved version.DiffThis version (01 Apr 2013 23:39) was approved by James Fitzgerald.The Previously approved version (20 Mar 2013 21:06) is available.Diff

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Table of Contents

CN-0251 Software User Guide

Overview

CN-0251 is a flexible signal conditioning circuit for processing signals of wide dynamic range, varying from several mV p-p to 20 V p-p. The circuit provides the necessary conditioning and level shifting and achieves the dynamic range using the internal programmable gain amplifier (PGA) of the high resolution analog-to-digital converter (ADC).

A ±10 V full-scale signal is very typical in process control and industrial automation applications; however, in some situations, the signal can be as small as several mV. Attenuation and level shifting is necessary to process a ±10 V signal with modern low voltage ADCs. However, amplification is needed for small signals to make use of the dynamic range of the ADC. Therefore, a circuit with a programmable gain function is desirable when the input signal varies over a wide range.

In addition, small signals may have large common-mode voltage swings; therefore, high common-mode rejection (CMR) is required. In some applications, where the source impedance is large, high impedance is also necessary for the analog front-end input circuit.

This user guide will discuss how to use the evaluation software to collect data from the EVAL-CN0251-SDPZ Evaluation Board (CN-0251 Board)

Required Equipment

General Setup

<html><br><br></html> <html><hr></html>

Connecting the Hardware

  1. Ensure the jumpers are populated on the EVAL-CN0251-SDPZ (CN-0251 Board) as depicted in the figure below.
    • JP1 and JP2 configure the analog inputs for single-ended or differential inputs
    • JP3 and JP4 configure the gain of the AD8475 to be 0.4x or 0.8x<html><br><br></html><html><br><br></html>
  2. Connect the Analog Discovery to the EVAL-CN0251-SDPZ (CN-0251 Board) as depicted in the figures below.
    • The waveform outputs should be connected to J1:2 (IN1-) and J1:3 (IN2+) of the CN-0251 Board.<html><br><br></html>
  3. Connect the +6V Power Supply to the screw terminal at J3.
  4. Connect the ±15V Power Supply to the screw terminal at J4.
  5. Connect the SDP-B Board to the CN-0251 Board

Setting up Digilent WaveForms

  1. Install Digilent WaveForms Software
  2. Use the USB Type-A to USB Micro-B cable to connect the Analog Discovery to the PC
  3. Open the file named cn0251_demo.dwfawg<html><br><br></html><html><br><br></html>
  4. Click the Run All Button<html><br></html>

Using the Evaluation Software

Software Control and Indicator Descriptions

  1. <html><a id=“1”><b>Connect/Reconnect Button</b></a></html>
    • When this button is pressed, the SDP-B Board makes a USB connection to the CN-0288 Board. A connection to the SDP-B Board must be made to use the software.
  2. <html><a id=“2”><b>Capture Data Button</b></a></html>
    • When this button is pressed, the SDP-B Board will collect conversion data and present the acquisitions in the chart.
  3. <html><a id=“3”><b>Save Data Button</b></a></html>
    • When this button is pressed, the software will save the data collected to a tab delimited ASCII spreadsheet file.
  4. <html><a id=“4”><b>Control Tabs</b></a></html>
    • Data - Clicking this tab brings the data collection chart to the front.
    • Analysis - Clicking this tab brings the data analysis histogram to the front.
    • Configure System - Clicking this tab brings the system configuration control to the front.
    • SDP Board Information - Clicking this tab brings the SDP Board Information indicators to the front.
  5. <html><a id=“5”><b>Input Channel Drop-Down Menu</b></a></html>
    • Clicking this drop-down menu selects the channel to capture data from.
  6. <html><a id=“6”><b>Input Range Drop-Down Menu</b></a></html>
    • Clicking this drop-down menu selects the analog input voltage range for the channel selected by the <html><a href=“#6”><b>Input Range Drop-Down Menu</b></a></html>.
  7. <html><a id=“7”><b>AD7192 Gain Indicator</b></a></html>
    • This indicator displays the gain currently programmed into the AD7192.
  8. <html><a id=“8”><b>AD8475 Gain Indicator</b></a></html>
    • This indicator displays the gain setting required from the AD8475.<html><br><br></html>

      Jumpers JP3 and JP4 on the EVAL-CN0251-SDPZ (CN-0251 Board) must be populated to reflect the value displayed by this indicator

  9. <html><a id=“9”><b>Samples to Capture Control</b></a></html>
    • This numerical control sets the number of samples to capture once the <html><a href=“#2”><b>Capture Data Button</b></a></html> is pressed.
  10. <html><a id=“10”><b>Display Unit Drop-Down Menu</b></a></html>
    • Clicking this drop-down menu allows you to select chart y-axis units to display.
  11. <html><a id=“11”><b>Chart Controls</b></a></html>
    • These controls allow the user to zoom-in, zoom-out, and pan through the data collected.
  12. <html><a id=“12”><b>System Status String Indicator</b></a></html>
    • This indicator displays a message to the user detailing the current state of the software.

<html><a id=“usb”><hr></a></html>

  1. Follow the instructions to properly install the software and connect the hardware as described in the previous sections.
  2. Open the file named CN0251.exe in the installation directory.<html><br><br></html>

    NOTE: If the software was installed to the default location it will be found at <html><br></html>C:\Program Files\Analog Devices\CN0251\CN0251.exe

    <html><br><br><br><br><br><br></html>

  3. Click the <html><a href=“#1”><b>Connect/Reconnect Button</b></a></html>. A window with a progress bar will load.<html><br><br></html><html><br><br></html>
  4. Upon success, the <html><a href=“#12”><b>System Status String Indicator</b></a></html> will display Ready to Capture Data<html><a id=“capture”><br></a></html>

Capturing Data

  1. <html><a href=“#usb”><b>Establish a USB Connection Link</b></a></html>.
  2. Click the <html><a href=“#5”><b>Input Channel Drop-Down Menu</b></a></html> to select the channel to convert
  3. Click the <html><a href=“#6”><b>Input Range Drop-Down Menu</b></a></html> to select the range of the analog input voltage.<html><br><br></html>

    Changing this control will change the <html><a href=“#8”><b>AD8475 Gain Indicator</b></a></html>. Please ensure that JP3 and JP4 on the EVAL-CN0251-SDPZ (CN-0251 Board) are populated to reflect the gain displayed by the <html><a href=“#8”><b>AD8475 Gain Indicator</b></a></html>.

  4. Input the number of samples to capture into the <html><a href=“#9”><b>Samples to Capture Control</b></a></html>
  5. Click the <html><a href=“#2”><b>Capture Data Button</b></a></html> and wait until acquisition is complete.<html><br><br></html>

Changing the Display Units

  1. Click the <html><a href=“#10”><b>Display Unit Drop-Down Menu</b></a> to select the units to display</html>.

Saving Data to a Spreadsheet File

  1. <html><a href=“#usb”><b>Establish a USB Connection Link</b></a></html>.
  2. <html><a href=“#capture”><b>Capture Data</b></a></html>.
  3. Click the <html><a href=“#3”><b>Save Data Button</b></a></html>.
  4. Browse to the directory location where the spreadsheet file is to be saved.
  5. Name the file.
  6. Click the OK Button.

<html><br></html>The software saves the spreadsheet file as ASCII text with columns separated by tabs.

resources/eval/user-guides/circuits-from-the-lab/cn0251.1364852263.txt.gz · Last modified: 01 Apr 2013 23:37 by James Fitzgerald

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