8/12/2019 RS-485 ligao a 2 ou 3 fios.pdf
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Ohio Semitronics, Inc. Page 1 of 3 Communication Connections
4242 Reynolds Drive For the Surface Mount Version
Hilliard, Ohio 43026 of the Digital Load Monitor
Phone: 614-777-1005 E-mail [email protected]
Connecting Multiple Digital Load Monitors to anRS-485 or RS-422 System
This paper applies to the surface mount version of the Digital Load Monitors, which have a barrier strip with 6
terminals to attach the communications cable.
The connection positions are:
+5 volts DC this is for the OSI IFC-4498A RS-422 to RS-432 converter only.
Common this is for the OSI IFC-4498A RS-422 to RS-432 converter only.
Tx+ Transmit +
TX- Transmit -
Rx+ Receive +
Rx- Receive -
If you are using the IFC-4498A RS-422 to RS-232 converter to connect to a COM port on your computer, theleads are labeled +5V, Com, Tx+, Tx-, Rx+, and Rx-. Connect these leads to the matching terminals on the
Digital Load Monitor (DLM) closest to your computer. The terminals labeled +5V and Com are used to supply
the converter with the required operating voltage. The 5V and Com should be connected only on the DLM that
is connected to the IFC-4498A. All other DLM meters should have these terminals open (no connection).
When using the IFC-4498A, a four-wire connection must be used (plus the power supply leads).
Note: The RS-485 standard was developed jointly by the Electronic Industries Association (EIA) and the
Telecommunications Industry Association (TIA). The EIA once labeled all of its standards with the prefix "RS"
(Recommended Standard). Many of us still use this designation but the TIA and EIA have officially replaced
the "RS" with "EIA/TIA" to help identify the origin of the standard.
Recommendations:
For RS-422 / RS-485 four-wire use two twisted pairs of 24AWG wires. One pair is for Tx+ and Tx- and the
second pair is for Rx+ and Rx-.
For RS-485 two-wire applications use one twisted pair of 24AWG wire.
Essential for minimizing reflections in two-wire systems are termination resistors. These should be 120-ohm
resistors at both ends. Many RS-485 ports already include the host end resistor. Check the instructions for the
port.
Maximum loads (DLMs) on a 4-wire system is 10.
Maximum loads (DLMs) on a 2-wire system is 32.
Each Digital Load Monitor on a two or four wire system must have a separate 4-digit address. The user may
assign the address using the software supplied with these meters.
8/12/2019 RS-485 ligao a 2 ou 3 fios.pdf
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Ohio Semitronics, Inc. Page 2 of 3 Communication Connections
4242 Reynolds Drive For the Surface Mount Version
Hilliard, Ohio 43026 of the Digital Load Monitor
Phone: 614-777-1005 E-mail [email protected]
+5V COM Tx+ Tx- Rx+ Rx- +5V COM Tx+ Tx- Rx+ Rx-+5V COM Tx+ Tx- Rx+ Rx-
Tx+ Tx- Rx+ Rx-
DLM Surface Mount
Version
DLM Surface Mount
Version
DLM Surface Mount
Version
Host RS-422 or RS-485
To additional DigitalLoad Monitors orother RS-422 Devices
if there are any.
+5V COM Tx+ Tx- Rx+ Rx- +5V COM Tx+ Tx- Rx+ Rx-+5V COM Tx+ Tx- Rx+ Rx-
DLM Surface Mount
Version
DLM Surface Mount
Version
DLM Surface Mount
Version
To additional DigitalLoad Monitors orother RS-485 Devicesif there are any.
Connecting multiple surface mount Digital Load
Monitors to a host with an RS-422 or RS-485 input.
4 Wire Connect ion
Connecting multiple surface mount Digital LoadMonitors to a host with an RS-485 input.
2 Wire Connect ion
Tx+ Tx- Rx+ Rx-
Host RS-485
120-ohm resistoron the last DLM.
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Ohio Semitronics, Inc. Page 3 of 3 Communication Connections
4242 Reynolds Drive For the Surface Mount Version
Hilliard, Ohio 43026 of the Digital Load Monitor
Phone: 614-777-1005 E-mail [email protected]
IFC-4498ARS-422 to RS-232
Converter.
+5V CO M Tx+ Tx- Rx + Rx - +5V CO M Tx+ Tx- Rx+ Rx -+5V CO M Tx+ Tx- Rx + Rx -
DLM Surface Mount
Version
DLM Surface Mount
Version
DLM Surface Mount
Version
To addit ional DigitalLoad Monitors orother RS-422 Devicesif there are any.
Connecting multiple surface mount Digital Load
Monitors to a host with using the OSI IFC-4498A
RS-422 to RS-232 converter.
Cable to the COMPort on a personal
computer.
+5 V CO M Tx + Tx- Rx+ Rx -
If you have any questions regarding the connections or use of the Ohio Semitronics, Inc. Digital Load Monitors
(DLM), please contact us at Ohio Semitronics, Inc.
There is a manual available that describes using these meters and that describes the communications protocol.If you require one of these manuals, please call or e-mail us.
August 3, 2001
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