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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 +50

o

C

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) su5
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.

Содержание MD9

Страница 1: ...INSTRUCTION MANUAL MD9 Multidrop Interface Revision 5 03 C o p y r i g h t c 1 9 8 7 2 0 0 3 C a m p b e l l S c i e n t i f i c I n c...

Страница 2: ...her 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 d...

Страница 3: ...on 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 So...

Страница 4: ...MD9 Multidrop Interface Table of Contents ii 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 This is a blank page...

Страница 5: ...ories 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...

Страница 6: ...ng 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...

Страница 7: ...r 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 Conta...

Страница 8: ...when necessary All MD9s in a system must be set at the SAME baud rate 9600 Baud 1200 Baud 300 Baud A B Short A B Open A B Short C D Short C D Short C D Open FIGURE 4 1 ID Switch and Baud Rate Selectio...

Страница 9: ...the battery voltage level The PS512M includes an AC wall transformer for AC operation A solar panel optional may be used if AC is unavailable A PS512M with a serial number less than 1712 does not supp...

Страница 10: ...n MD9 See the timing diagram in Appendix C Upon detecting activity on the coax line remote MD9s convert from State 0 to State 2 State 2 is a sleep mode in which the MD9 begins a timing routine to dete...

Страница 11: ...dataloggers in a network have been interrogated When all data for a particular time period has been collected and stored by the computer the computer s DTR line is released causing the local MD9 to r...

Страница 12: ...MD9 Multidrop Interface 8 This is a blank page...

Страница 13: ...Conductor 20 AWG solid copper 032 Jacket Material PVC Jacket O D 235 Shield Braided tinned copper 100 coverage Resistance 10 1000 Capacitance 16 2pf ft Impedance 75 Ohms Attenuation at 1 MHz 0 29 db...

Страница 14: ...This is a blank page...

Страница 15: ...The marking time must be greater than one times the inverse of BR and the marking time and ADDRESS must be completed within 100 msec This is to say that a 9600 baud the BREAK must be greater than 1 1...

Страница 16: ...This is a blank page...

Страница 17: ...10 12 0011 0000 55 1110 1100 98 0100 0110 13 1011 0000 56 0001 1100 99 1100 0110 14 0111 0000 57 1001 1100 100 0010 0110 15 1111 0000 58 0101 1100 101 1010 0110 16 0000 1000 59 1101 1100 102 0110 0110...

Страница 18: ...000 1001 188 0011 1101 231 1110 0111 146 0100 1001 189 1011 1101 232 0001 0111 147 1100 1001 190 0111 1101 233 1001 0111 148 0010 1001 191 1111 1101 234 0101 0111 149 1010 1001 192 0000 0011 235 1101...

Страница 19: ...e can be modified to connect to the datalogger s power terminals as follows 1 Unplug field cable from datalogger and SC532A 2 Cut off DB9 connector 3 Remove cable sheath exposing positive RED wire and...

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Страница 21: ...This is a blank page...

Страница 22: ...campbellsci com br suporte campbellsci com br Campbell Scientific Canada Corp CSC 11564 149th Street NW Edmonton Alberta T5M 1W7 CANADA www campbellsci ca dataloggers campbellsci ca Campbell Scientifi...

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