Campbell Scientific MD9 User Manual

INSTRUCTION MANUAL
MD9 Multidrop Interface
Revision: 5/03
Copyright (c) 1987-2003
Campbell Scientific, Inc.

Warranty and Assistance

The MD9 MULTIDROP INTERFACE is warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and ser vice for twelve (1 2) months from date of shipment unless specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products. The customer shall assume all costs of removing, reinstalling, and shipping defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL SCIENTIFIC, INC. will return such products by surface carrier prepaid. This warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products which have been subjected to modification, misuse, neglect, accidents of nature, or shipping damage. This warranty is in lieu of all other warranties, expressed or implied, including warranties of merchantability or fitness for a particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special, indirect, incidental, or consequential damages.
Products may not be returned without prior authorization. The following contact information is for US and International customers residing in countries served by Campbell Scientific, Inc. directly. Affiliate companies handle repairs for customers within their territories. Please visit www.ca mpbellsci.co m to determine which Campbell Scientific company serves your country. To obtain a Returned Materials Authorization (RMA), contact CAMPBELL SCIENTIFIC, INC., phone (435) 753-2342. After an applications engineer determines the nature of the problem, an RMA number will be issued. Please write this number clearly on the outside of the shipping container. CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____ 815 West 1800 North Logan, Utah 84321-1784
CAMPBELL SCIENTIFIC, INC. does not accept collect calls.
MD9 Multidrop Interface Table of Contents
PDF viewers note: These page numbers refer to the printed version of this document. Use the Adobe Acrobat® bookmarks tab for links to specific sections.
1. Introduction.................................................................1
2. System Description ....................................................1
3. Software and Datalogger Compatibility ....................3
4. ID and Baud Rate Selection .......................................3
5. Maximum Number of Dataloggers and
Coax Length...........................................................4
6. Telephone to MD9 Network........................................5
7. Operation.....................................................................6
A. Cable Specifications and Source References......A-1
B. Break/Address Timing........................................... B-1
C. Setting the Station ID.............................................C-1
D. SC532A ...................................................................D-1
Tables
1-1 Specifications ...........................................................................................1
4-1 ID Settings for MD9 Connected to Computer..........................................4
Figures
1-1 MD9 Multidrop Interface.........................................................................2
2-1 System Description...................................................................................3
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MD9 Multidrop Interface Table of Contents
4-1 ID Switch and Baud Rate Selection Jumpers........................................... 4
6-1 Telephone to MD9 Conversion................................................................ 6
B-1 Break/Address Timing Diagram.......................................................... B-1
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MD9 Multidrop Interface

1. Introduction

The MD9 Multidrop Interface functions as a direct wire link between a computer and a Campbell Scientific datalogger via coax cable. MD9s may be networked thereby permitting a computer to address and communicate with up to 254 dataloggers. Total coax length may be up to 3 miles when fewer dataloggers are used.
With the communication link initiated and controlled by an IBM PC or clone using Campbell Scientific's telecommunication software, the operation of the MD9 in the system is transparent to the user. Call back from a remote datalogger via MD9 is not possible.
TABLE 1-1. Specifications
Size: 6.5 X 3.5 X 1.25 in. Weight: 5 oz. Accessories: SC12 cable, BNC "T" connector Voltage: 5 Volts from datalogger or SC532(A) Current:
State 0 "Standby" 1.2 mA State 1 "Active" 17 mA (when transmit line drives network) 80 mA State 2 "Sleep" 3 mA State 3 Pull ring line & buffer bytes 17 mA
Temperature range: -25 to +50oC Baud rates: 9600, 1200, 300 Carrier frequency: 1.2 MHz Communication cable: RG59/U Coax Cable connector: BNC

2. System Description

The block diagram in Figure 2-1 depicts the connection of a computer to a network of Campbell Scientific dataloggers using MD9s.
Connection of the MD9 to the computer's RS-232 SIO port is made via the SC532(A) 9 Pin Peripheral to RS-232 Interface. The SC532(A) supplies +5 VDC power to the MD9 as well as converts the MD9's CMOS voltage levels to voltage levels consistent with RS-232 requirements. A computer with the PC201 card installed could use the SC925 Cable to connect directly to the MD9.
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MD9 Multidrop Interface
The MD9 at the computer is connected to one or more other MD9s with coax cable terminated with BNC connectors. Refer to Appendix A for cable specifications and source references.
The MD9 at the datalogger is connected via an SC12 cable (supplied with the MD9) and is powered from the datalogger SERIAL I/O port.
Each MD9 includes a BNC "T" connector to allow for coax in/ coax out. "T" connectors on MD9s at the beginning (computer) and end (last datalogger) of the network must be terminated with 75 ohm Coax Terminators in order to prevent signal reflection from one end of the cable to the other. Place terminators on the ends of the main cable only. Any branch cables from the main cable to an MD9 should be less than 10 feet in length. No terminator is used on the T connector at the MD9 on a branch. (Figure 2-1).
NOTE
There are two ground terminals located between the Serial I/O and Coax Connectors on the MD9. When installing the MD9, a 16AWG or heavier wire should be connected from earth ground to one of these terminals.
FIGURE 1-1. MD9 Multidrop Interface
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MD9 Multidrop Interface
FIGURE 2-1. System Description

3. Software and Datalogger Compatibility

PC208 Software Index #5348-00 or higher is required for use with MD9s. Customers using older software may purchase a software update for a nominal charge by contacting Campbell Scientific.
The following dataloggers may be used in an MD9 network.
CR10 all 21X SN6195 or higher 700X Control Module SN1670 or higher
21Xs and 700Xs with lower SNs require a resistor modification which permits the respective 5 Volt power supplies to source enough current to operate an MD9. Contact Campbell Scientific customer service if your datalogger requires this modification.

4. ID and Baud Rate Selection

Each MD9 in an MD9 network must have a unique ID. The ID is set by the ID select switch (Figure 4-1). This switch is located under the cover, and can be accessed by removal of the four cover screws.
Appendix C gives a complete list of ID and switch settings.
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