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
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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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