Cable Length and Sensor Type

There should be added more details for your inquire for sensor's signal specs: mA, mV, V, or whatever else. I'm personally using thumb rule don't exceed some hundreds meters between signal source and PLC unless there are using repeaters (signal normalizers or/and signal conditioners).

Cable are to be shielded. Hope someone here will provide more details for that as I'm not aware of western national standards for wiring and cables' nomenclature.

Carambas right, you really need to provide more info.

What level signal? How far between the sensor and PLC? What kind of electrical noise environment are you in? How many signals? What is the bandwidth of the signals? How big a problem is it if the sensor signal gets corrupted?

Ok.

The sensor is giving 4 to 20 ma.

The sensor out put is digital.

It is cabled and not working on radio frequencie.

The electrical disturbances are less as this is installed at a lonely sea shore.

It is not much important if signal is delayed. But, the delay should not be more than 1 sec.

Okay, it had been discussed here on cr4 .

Vulcan has given complete answer for. Last year I'd finished and are maintaining now project where 4-20 mA signals from sensors had been gathering on PLC inputs from up to 400 m distance with no problems in extremely hazardous conditions.

Delays are mostly caused the DAC/ADC converting performances than distance between PLC and sensor(s).

If your sensor is giving current output and if cable is of sufficient gauge to give minimum reistance, it should be possible to transmit the signal to long distance.

Voltage output will be a problem.

Additional data such as type of output and distance between sensor and the PLC will help in deciding as others have already said.

What are the specs of your sensor?

What are the specs of your PLC input?

How far is far away?

Your PLC input has voltage specs for low or OFF signals and high or ON signals. For example: Voltages below 3 volts are considered as LOW or OFF. Voltages above 15 volts are considered as HIGH or ON.

Your sensor should also have specs that say how much current or voltage it puts out when ON or OFF.

With these information, you should be able to calculate how long your wire can be if you obtain its Ω/meter. All you need is Ohm's Law. The bigger the wire, the longer the distance.

I've strung sensors on cables up to 200 meters with no problem.

regards,

Vulcan

Have you considered a battery/solar operated data collection system on-site? Housing a data collection PLC close to the sensors is often a better solution than long lead lengths.