1km Water Level Controller

[garg29]

I'm designing a water level controller. It has to be designed using conventional method of (probes in water). Actually the distance between the tank and base unit is almost 1 Km . wires have been layed out. I want to know what method should i take to do these level sensings (10 levels) at such a long distance. i mean should i use some special amplifying stage filters etc. One thing more I think a low amplitude ac signal should be transimitted in water to prevent salt formation. what should be the frequency of this signal. Do i need a amplifier in base unit for transmiting a strong signal for this distance range. One last thing i cannot design any unit at the tank end. only one base unit.

Thanks.

With best regards,
garg

 

[plusminus]

It is not really clear to me how you measure method works but the best tranport method over such a long distance is:
1) a current loop (see industrial systems 4-20mA) In this way you can also supply a small device (<4mA) to convert the meassured level.
2) symetric data bus like RS485 /422. Convert the level to a digital serial signal.

You will have a lot of losses and noise over this distance, so an AC (amplitude)signal to measure is a little tricky. Although changing the frequency by the level is maybe an option. (100Hz level1, 150Hz level2 etc)

 

[amprakashj]

A.C lines travels a long distance. You can sense the probe to the system using A.C supply. While sensing the probe in the system you can use a D.C conversion, i.e., you can use a diode in the system to monitor the probe signal.

 

[klystron]

Can you use a 5 pair cable ? (10 conductors)

 

[luben111]

I would suggest you put some small controller near the probes and communicate through the long wires with RS485 (up to 1.5km guaranteed). In total you'll need 4 wires (+, -, DATA_OUT+, DATA_OUT-). Sending the analog signals on 1km sounds insane