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B&B Electronics 485T Manual

Rs-422/rs-485 line tester
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Not Recommended for New Installations.
Please contact Technical Support for more information.
RS-422/RS-485 Line Tester
Model 485T
Documentation Number 485T1995
This product
Designed and Manufactured
In Ottawa, Illinois
USA
of domestic and imported parts by
B&B Electronics Mfg. Co. Inc.
707 Dayton Road -- P.O. Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 433-5105
Internet:
http://www.bb-elec.com
orders@bb-elec.com
support@bb.elec.com
1992 B&B Electronics -- Revised August 1992
Documentation Number 485T1995 Manual
Cover Page
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 433-5105

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Summary of Contents for B&B Electronics 485T

  • Page 1 Not Recommended for New Installations. Please contact Technical Support for more information. RS-422/RS-485 Line Tester Model 485T Documentation Number 485T1995 This product Designed and Manufactured In Ottawa, Illinois of domestic and imported parts by B&B Electronics Mfg. Co. Inc. 707 Dayton Road -- P.O. Box 1040 -- Ottawa, IL 61350...

  • Page 2: Table Of Contents

    TABLE OF CONTENTS INTRODUCTION ...1 RS-422 AND RS-485 STANDARDS ...1 CONTROLS AND CONNECTIONS ON THE 485T ...6 ERMINALS ...6 ROUND ERMINAL ...7 HRESHOLD OSITIVE HRESHOLD EGATIVE HRESHOLD RS-422/RS-485 S WITCH ERMINATION WITCH ...8 OWER RS-232 D RS-422/485 TEST ...9 Documentation Number 485T1995 Manual B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350...

  • Page 3: Introduction

    INTRODUCTION The Model 485T Tester can be used to check the condition of signals at any node on an RS-422 or RS-485 network. The tester determines if the maximum permissible negative or positive voltages are being exceeded. If these voltage levels are exceeded it is possible to damage the RS-422/485 receivers and drivers.
  • Page 4 high and vice-versa. Also, the drivers are capable of driving a wire with as much as 25 times more capacitance before the signal is badly distorted. Most system designers try to minimize the number of signals used because these standards take two wires per signal. This is one reason most RS-422 and RS-485 systems are either two-wire with ground or four-wire with ground.
  • Page 5 Documentation Number 485T1995 Manual B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350 PH (815) 433-5100 -- FAX (815) 433-5105...
  • Page 6 Documentation Number 485T1995 Manual B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350 PH (815) 433-5100 -- FAX (815) 433-5105...
  • Page 7 Documentation Number 485T1995 Manual B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350 PH (815) 433-5100 -- FAX (815) 433-5105...

  • Page 8: Controls And Connections On The 485T

    The two signal lines used in an RS-422 or RS-485 network should be labeled A and B. These lines should be connected to the A and B terminals of the 485T Tester. If your lines are not marked (or are marked using another method) you can use a DC voltmeter to determine which is which.

  • Page 9: Threshold Pot

    Threshold Pot The large pot in the center of the 485T is the threshold pot. In order for RS-422/485 to work properly, you should have a differential input voltage of more than .2 volts across the two lines at the RS- 422/485 receiver.

  • Page 10: Rs-422/Rs-485 Switch

    In some complicated multi-drop networks it may be hard to determine exactly were the “ends” are. A 100 ohm one-half watt termination resistor is included in the 485T. It may be helpful if you are testing an existing network with no terminations and want to see what happens if you terminate it at one point.

  • Page 11: Rs-422/485 Test

    You should first check that the RS- 422/RS-485 switch is in the proper position and that the Signal Ground is connected correctly to the 485T. Refer to B&B Electronics' free RS-422/485 Application Note for information on proper grounding of your network.
  • Page 12 2 next, etc., and node 5 is at the far end. If you connect the 485T Tester to node 1 and watch while data is sent from node 2, there will only be 1000 feet of wire and the signal should be fairly strong.
  • Page 13 You can then use the 485T Tester to monitor the data that is being sent or received on your network. If you have a datascope or a computer running a datascope-like program you can connect it to the RS-232 DATA OUT connector on the 485T. A typical program would be BreakOut II which is available from B &...
  • Page 14 Documentation Number 485T1995 Manual B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350 PH (815) 433-5100 -- FAX (815) 433-5105...

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