Acr | Fluke DSP-100, DSP-2000 instruction

Basic Cable Testing 7

ACR

A negative reflection percentage indicates that the polarity of the reflection is the opposite of the original signal. Negative reflections are caused by abrupt decreases in the cable’s impedance, such as those caused by mismatches in cable types or shorts on the cable.

The results plotted in Figure 7-10 are the results from a TDR test on pair 4,5 in a good twisted pair cable. The results show a positive anomaly caused by the open end of the cable at about 219 feet. Note that the left edge of a TDR reflection represents the location of the anomaly on the cable, while the peak of the reflection represents the size of the anomaly.

The test tool’s TDR plot includes a movable cursor with a readout that displays the cursor’s position and the reflection percentage of the anomaly at the cursor’s position. You can move the cursor left and right by pressing the L R keys on the test tool. Figure 7-10 shows the cursor positioned near the beginning of an anomaly.

ACR

ACR (attenuation to crosstalk ratio) is the difference between NEXT in dB and attenuation in dB. The ACR value indicates how the amplitude of signals received from a far-end transmitter compares to the amplitude of crosstalk produced by near-end transmissions. A high ACR value means that the received signals are much larger than the crosstalk. In terms of NEXT and attenuation values, a high ACR value corresponds to high NEXT and low attenuation.

7-19

Image 131

Fluke DSP-100, DSP-2000 user manual Acr

Contents

DSP-100/2000 Limited Warranty & Limitation of Liability Table of Contents DSP-100/2000 Appendices DSP-100/2000 List of Tables Tests Run per Test Standard During an Autotest List of Figures Plot of NEXT, Attenuation, and the Resulting ACR Introduction Overview of Features DSP-100/2000 Standard Accessories Standard Accessories Using This Manual DSP-100/2000 International Electrical Symbols Safety and Operational Information DSP-100/2000 Key Powering the Test ToolUsing the Menus Quick Start Quick Configuration Settings Description Quick ConfigurationSetup Setting Press ! Choice Asterisk and Test Tool Accuracy Results within Accuracy Range Autotest on Twisted Pair Cable Horizontal Cross Connect Blocks Meters Getting Started Autotest on Coaxial Cable Autotest on Coaxial Cable DSP-100 DSP-2000 Main Unit Features Main Unit Features Description Feature Standard and Smart Remote Features Remote Features Remote Connectors and Features Remote Features Off Rotary SwitchStrap and Bail Autotest Monitor Single Test Setup Smart Remote Model DSP-100 Turning On the Test ToolPrint Special Functions Performing a Self-Test Selecting a Language for Displays and Reports Controlling the Backlight Configuring the Test ToolOvervoltage Test Noise Test Selecting a Power Line Filter Frequency Adjusting the Display Contrast Selecting a Test Standard and Cable Type Selecting an Average Cable Temperature Selecting a Conduit Setting Selecting a Numeric Format Selecting a Length Unit Setting the Date and Time Enabling or Disabling the Audible Tones Setting the Power-Down Timer Remote Lights, Messages, and Audible Tones Smart Remote Ready Remote End Testing Battery Status Remote Communication Error Battery Status Display Autotest Softkeys Autotest Smart Autotest Link Performance Grade Result Headroom Automatic Diagnostics Model DSP-2000 Automatic Diagnostics Model DSP-2000 Autotest Results for Twisted Pair Cable Wire Map Test Autotest Results for Twisted Pair Cable Length Resistance Characteristic Impedance Propagation Delay and Delay Skew Items on the Attenuation Results Screen Description Attenuation Gc10c.eps Items on the Next Results Screen Description Next Test Next Plot Screen Items on the Next Plot Screen Description ACR Items on the ACR Results Screen Description ACR Plot Screen Items on the ACR Plot Screen Description Items on the RL Results Screen Description Return Loss RL RL@REMOTE Model DSP-2000 Psnext Power Sum Next Model DSP-2000 Connector Autotest Results for Coaxial Cable No Reflection Anomaly Saving Autotest Results Gc15c.eps If Memory is Full Autotest ReportAutomatically Incrementing the Cable Identification Name Part of an Autotest Report for Twisted Pair 10. Autotest Report for Coaxial Cable DSP-100/2000 Single Tests for Twisted Pair Cable Running Individual Tests Scanning Function When to Use a Remote Unit Remote Requirements for Cable Tests Remote Unit Test Running a Single Test on Twisted Pair Cable Running Individual Tests Running the TDX Analyzer TDX Analyzer Items on the TDX Analyzer Results Screen TDX Analyzer Results TDX Analyzer Plot TDR Test How to Terminate the Cable Running the TDR Test on Coaxial Cable Running the TDR Test on Twisted Pair Cable Items on a TDR Results Screen Twisted Pair Results TDR Results ScreenTDR Plot Screen Single Test Results for Twisted Pair Cable Impedance Wire MapNext and NEXT@REMOTE Running a Single Test on Coaxial Cable Single Tests for Coaxial CableReturn Loss RL and RL@REMOTE Single Tests for Coaxial Cable Single Test Results for Coaxial Cable Monitoring Network Activity Monitoring Network Activity DSP-100/2000 Items on the Traffic Monitor Screen Description Changing the Impulse Noise Threshold Identifying Hub Port ConnectionsMonitoring Impulse Noise Running the Impulse Noise Test Use Dto highlight Impulse Noise on RJ45 Items on the Noise Monitor Screen Description Determining Hub Port Capabilities Model DSP-2000Noise Test Results Using the Tone Generator Model DSP-2000 Printing Test Reports Viewing and Printing Saved Reports Printing Configuring the Serial PortPrinter Interface Cable Viewing and Printing Saved Reports Printing Test Reports DSP-100/2000 If the Printer Does Not Respond Viewing, Renaming, and Deleting Test Reports Calibrating the Test Tool Calibrations and Custom Test Standards Connections for Self-Calibration DSP-2000 Shown Use Dto highlight Determine Cable NVP NVP Calibration Configuring a Custom Cable Page DSP-100/2000 LAN Cable Construction Basic Cable Testing Twisted Pair Cable Construction Twisted Pair Cable 568A Coaxial Cable Construction Coaxial Cable Attenuation Attenuation of a Signal Sources of Electrical Noise Noise Characteristic Impedance Minimizing Impedance Discontinuities Crosstalk and Near-End Crosstalk Next Locating Next Problems A TDX Analyzer Plot Basic Cable Testing Split Pairs and Next Incorrect Wiring Split Pair Minimizing Crosstalk NVP and Length Measurements Nominal Velocity of Propagation NVP NVP Calibration Time Domain Reflectometry TDR Short Reflections from Opens Reflections from Other Discontinuities Reflections from Shorts Interpreting the TDR Plot Cable Termination ACR Frequency in MHz Limit in dB Finding Cable Faults Troubleshooting Basics Test Failure Identifying Cable Faults Likely Causes of Failure Identifying Cable Faults Examples of Test Displays and Plots Identifying Cable Faults Test Failure Next test fails Impedance anomaly is Detected DSP-100/2000 Cleaning and Storage Maintenance Removing the Battery in the Standard Remote Replacing the NiCad Battery Pack Removing the NiCad Battery Pack Internal Lithium Backup Battery If the Test Tool Fails Service Center Repair Symptom 6 Self calibration fails Troubleshooting the Test Tool Symptom 1 Display is blankSymptom 2 Remote unit is not detected Symptom 3 Test results appear to be incorrect Part Number Replacement PartsReplacement Parts Description Compatibility with Remote Units SpecificationsService Center Calibration Period Self-Calibration Period Time for Autotest Cable Types TestedTest Standards Length Test Propagation Delay TestLength Test Specifications Propagation Delay Test Specifications Next DC Loop Resistance Return Loss TDX Analyzer Specifications for Cables 100m 328 ftTDR Specifications for Cables 100m 328 ft Serial Interface Impulse NoiseModel DSP-100 LAN Traffic Model DSP-2000 LAN Traffic PC Interface Cable Connections Test Tool End DB9S female 25-pin ConnectorPC Interface Cable Environmental Requirements Power Input Ratings Operating Environment Specifications Memory DimensionsWeight Certifications Display RJ45 ConnectorWarranty DSP-100/2000 Appendices Page Introduction Using DSP-LINK Preparing for Data Transfer Installing DSP-LINKConnecting to a PC Figure A-1. Connecting the Test Tool to a PC Configuring the Serial Ports Communication Problems Detailed Test Data Quick Plot DSP-LINK Functions DSP-100/2000 Table A-3. Formats for Uploaded Reports Courier Point Size Formatting Hints for Uploaded Reports Getting Software Updates from Fluke Downloading New Test Standards Downloading New Software 100BaseTX 10Base210BaseT Bandwidth Baseband SignalingBroadband Signaling Auto-Negotiation Crossed Pair CapacitanceChannel Collision EIA 568A CrosstalkCSV Data Download Impedance Discontinuity Hardware Flow ControlHorizontal Cabling Horizontal Cross-Connect Packet Propagation DelayLink Pulse Near-End Crosstalk Next Screened Twisted Pair ScTP Reversed PairRJ45 Runt Packet Token Ring Split PairTDXä Terminator XON/XOFF Flow Control DSP-100/2000 Tests Run per Test Standard During an Autotest Next Tests Run per Test Standard During an Autotest C Prop. Return Loss Delay2 Delay Skew2 TP-PMD Return Loss Prop Delay2 Delay Skew2 DSP-100/2000 Index DSP-LINK Next DSP-100/2000 Index DSP-100/2000 Manual Supplement Change #1 Wire Map Displays Displayed Schematic Description Wire Map Condition Wire map display showing an open on pair 1 Wire map display showing a split pair on pairs 1, 2 and 3 Change #3