i need to get the MODBUS on RS485 to 2.5 Kms. We may get power supply in between to install a black box or booster. Please advice.

Regards,
Rajiv Bavishi

 

If you are not in need of multidrops I would use a Black Box ME794 Micro Driver which is good for over 20 kM.

 

YOU MAY:
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1) Check the documentation of your RS485 Transmitter.

Some RS-485 Transmitters have enough power to transmit the signals much further than 1km, simply by increasing the cross-section of the copper conductor of the cable. You may consider the use of a cable with bigger cross-section, if applicable.

2) Use a "Fibre Optic to Copper Converter".

Characteristics of the Fibre Optic Cable to be used depends upon the projected "Fibre Optic Budget". The word "BUDGET" here does not necessarily imply the cost. It implies how far you want the signal to reach. There are plenty types and methods to select Fibre Optic Cables from.

3) Use a Short Haul Modems.

They normally help transmitting signals for more than 18 miles on STP cables in Duplex or Simplex mode (2-wire or 4-wire between both Short Haul Modems).

These are guidlines.

With those guidlines above, may not need to use any "relay" or "booster" station to transmit the signal for 2.5km. 2.5km is not a relatively long distance.

You may study each solution and opt for the one that is convenient for your application.

Regards,
Ashraf

 

Is the wire/cable already in place? If not, consider wireless.

Almost all countries allow some license free wireless (radio) communications. 2+ km is well within the range of commercially available wireless radios, many of which are designed to handle Modbus.

Carl