MD485 RS-485 Multidrop Interface
Increases Communication Options
Adds data link possibilities among dataloggers, PCs, and sensors
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications

Overview

The MD485 is an intelligent RS-485 interface that permits a PC to address and communicate with one or more dataloggers over a distance of up to 1200 m. This interface also supports datalogger-to-datalogger communication, callback from a remote datalogger, PC-to-printer communications, and digital camera-to-datalogger connections.

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Benefits and Features

  • Compatible with most Campbell Scientific dataloggers
  • Can be used with a phone modem, Ethernet link, or spread spectrum radio to extend the distance between the datalogger and PC
  • Increases the distance allowed between a CC5MPX digital camera and a PakBus datalogger
  • Extends the distance between AVW200 Vibrating-Wire Interfaces for situations where wireless communication is impractical
  • Internal buffering ensures that data is not lost during transmission and allows each side to operate at different baud rates
  • Includes gas tubes on the RS-485 ports and a ground lug for better surge protection
  • Communicates at rates up to 115.2 kbps

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Detailed Description

The MD485 includes three ports (RS-232, CS I/O, RS-485) for connecting a PC, a datalogger, or another MD485. Any two ports can be used at a time.

The MD485 can be configured to provide transparent communications, MD9 emulation, and PakBus networking. Although the MD485 can emulate an MD9, the MD485 can not be added to an existing MD9 network. PakBus networking requires the dataloggers to use the PakBus communications protocol. PC400 or LoggerNet software is used to initiate and control the communications link.

Required Equipment

The MD485 is shipped with the 10873 cable and SC12 cable for connecting it to a PC or datalogger. Point-to-point and point-to-multipoint networks use the following equipment:

  1. PC running PC400 or LoggerNet software
  2. At the computer site, an MD485 is connected to the computer via a pn 10873 cable.
  3. At each datalogger site, an MD485 is connected either to the datalogger’s CS I/O port (not compatible with the CR200(X)-series) or the datalogger’s RS-232 port (not compatible with the CR510 or CR10X). The SC12 serial cable connects an MD485 modem to the CS I/O port. The pn 18663 9-pin male to 9-pin male null modem cable connects the MD485 to the RS-232 port.
  4. The CABLE2TP-L Two-Twisted-Pair 22-AWG Cable connects an MD485 to another MD485. Please note that when communicating at maximum distances and high data rates, a cable with polyethylene insulation is recommended.
  5. CR200(X)-series, CR510, CR800, CR850, CR10X, CR1000, or CR3000 datalogger.
  6. Power supply 
  7. Environmental enclosure. At each field site, the datalogger, power supply, and MD485 should be housed in the enclosure if the equipment is not located in a building.

Powering the MD485

AC power is typically used at the computer site; a pn 15966 wall charger is required. At the field site, the MD485 is powered by the datalogger through its CS I/O port. If the MD485 is connected to the datalogger’s RS-232 port instead of the CS I/O port, or if the datalogger was purchased before 12/97, a pn 14291 Field Power Cable is required. Phone-to-MD485 and spread spectrum radio-to-MD485 networks also require a power supply with a null modem port . An A100 adapter used with a PS150 or PS200 power supply provides this capability. The PS150 or PS200 is recharged via a wall charger or a solar panel.

Specifications

Baud Rates 1200, 9600, 19.2k, 38.4k, 57.6k, 115.2k bps
Voltage 12 Vdc (from datalogger or pn 15966 wall charger)
Surge Complies with IEC61000-4-5, test level 3 (±2 kV, 2 Ω coupling impedance)
Temperature Range
  • -25° to +50°C (standard)
  • -55° to 85°C (extended)
Maximum Cable Length 1,219 m (4,000 ft)
Dimensions 15.88 x 6.35 x 1.91 cm (6.25 x 2.5 x 0.75 in.)
Weight 127.6 g (4.5 oz)

Current Drain

Standby Mode 1.2 mA
Communicating 2 to 7 mA

Power

Standby Mode 14.4 mW
Communicating 24 to 84 mW

ESD

Air Discharge Complies with IEC61000-4-2, test level 4 (±15 kV)
Contact Discharge Complies with IEC61000-4-2, test level 4 (±8 kV)

Compatibility

Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.

Dataloggers

Product Compatible Note
21X (retired)
CR10 (retired)
CR1000
CR10X (retired)
CR200X (retired)
CR206X (retired)
CR211X (retired)
CR216X (retired)
CR23X (retired)
CR295X (retired)
CR300 Use a 18663 null modem cable.
CR3000
CR500 (retired)
CR5000 (retired)
CR510 (retired)
CR6 The CR6 has integrated RS-485.
CR800
CR850
CR9000 (retired)
CR9000X

Mounting Equipment

Product Compatible Note
ENC10/12
ENC10/12R
ENC12/14
ENC14/16
ENC16/18

Additional Compatibility Information

Enclosure Considerations

A desiccated, non-condensing environment is required. The MD485 includes built-in keyhole flanges for mounting to the backplate of a Campbell Scientific enclosure.

Combining with Other Devices

The MD485 can be combined with our AVW200-series Vibrating-Wire Interfaces, CC640 Digital Camera, Ethernet links, phone modems (including cellular), and spread spectrum radios. Field site equipment should be housed in an environmental enclosure. Information about configuring the other devices is provided in the user manuals.

Power Considerations

AC power is typically used at the computer site; a pn 15966 wall charger is required. At the field site, the MD485 is powered by the datalogger through its CS I/O port. If the MD485 is connected to the datalogger’s RS-232 port instead of the CS I/O port, or if the datalogger was purchased before 12/97, a pn 14291 Field Power Cable is required. Phone-to-MD485 and spread spectrum radio-to-MD485 networks also require a power supply with a null modem port. An A100 adapter used with a PS150 or PS200 power supply provides this capability. The PS150 or PS200 is recharged via a wall charger or a solar panel.

Downloads

MD485 OS v.05 (583 KB) 04-06-2012

Current MD485 operating system. Requires the Device Configuration Utility.

View Update History

Device Configuration Utility v.2.17 (46.4 MB) 02-13-2018

A software utility used to download operating systems and set up Campbell Scientific hardware. Also will update PakBus Graph and the Network Planner if they have been installed previously by another Campbell Scientific software package.

Supported Operating Systems:

Windows 10, 8.1, 8, and 7 (Both 32 and 64 bit)

View Update History

Frequently Asked Questions

Number of FAQs related to MD485: 13

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  1. No. Isolation circuitry is not always needed, and it presents a significant increase in power consumption for battery-operated stations.  For situations where external isolation modules are required, external isolation modules can be added between stations.

  2. No. The MD485 is configured to be a serial converter between two of the interfaces. The MD485 serves to convert CS I/O to RS-485, RS-232 to RS-485, or CS I/O to RS-232.

  3. RS-485 networks should follow a bus topology whenever possible (devices daisy-chained in a linear fashion). The total amount of cable used in a single network should not exceed 1,200 m. An RS-485 repeater or a datalogger with multiple MD485 devices can be used to extend the length of a network or to create more complex network topologies.

  4. No. The RS-485 data transceivers used in the MD485 feature fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted. Because of this, biasing resistors are not needed. The transceivers also feature reduced slew-rate drivers that minimize electromagnetic interference (EMI) and reduce reflections. Because of this, termination resistors do not need to be used for most applications.

  5. 256 MD485 devices can exist on a single bus. The MD485 presents ⅛ of a unit load (electrical impedance load) to the network. An RS-485 network should not exceed 32 unit loads:  256 ∙ ⅛ = 32.

  6. Absolutely. The RS-485 interface of the MD485 meets the EIA/TIA-485 standards for half-duplex communications. Campbell Scientific customers have used the MD485 in conjunction with many other off-the-shelf RS-485 interfaces.

  7. Typically, only one MD485 is connected to a datalogger. Sometimes two are connected to create different network segments. Technically, however, one MD485 can be connected to each datalogger serial port, and up to five MD485 devices can be connected to a single datalogger CS I/O port.

  8. No. The device can also be connected directly to other devices such as a computer, radio, cellular modem, serial server, or other vendor RTU. When it is not connected to a datalogger, the MD485 is most commonly used to create a multidrop network behind another communications peripheral or off a computer’s serial port.

  9. The MD485 is compatible with nearly any serial line communications protocol. Most notably, the MD485 is regularly used for PakBus, Modbus RTU, Modbus ASCII, and DNP3.

  10. The MD485 provides enhanced performance when using PakBus communications. Additionally, the MD485 consumes very little power when idle, making it ideal for remote battery-powered installations. The MD485 also provides excellent surge/ESD (electrostatic discharge) protection and an integrated CS I/O port for plug-and-play operation with Campbell Scientific dataloggers.

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