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Electrode Sensor

10/18/2014 6:19 AM

There are normally 3 nos electrode sensors used in tank to start and stop pump operation. Shortest rod is used to stop pump during high water level or tank fulled. What is the function of the middle length and longest ? Which suppose to start running a pump ? Please advise.

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#1

Re: electrode sensor

10/18/2014 6:32 AM

It depends on the particular installation. Some possibilities include low alarm, start pump, stop pump, and high alarm. If you have three electrodes, one of these functions has probably been excluded.

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#2

Re: electrode sensor

10/18/2014 6:38 AM

Could be that the long rod is common.

Current between short rod and common: stop pump.

No current between middle rod and common: start pump.

But that's a guess - we can't see your control circuit from here.

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#3

Re: electrode sensor

10/18/2014 12:08 PM

If your peak consumption rate is slightly greater than the pump rate it is better to start the pump on the middle sensor. For other periods you can use the bottom sensor to reduce short runs.

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#4
In reply to #3

Re: electrode sensor

10/18/2014 12:17 PM

Is there a crystal ball that tells which is which? Or would that just be the fifth sensor?

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#5

Re: electrode sensor

10/18/2014 3:07 PM

The middle sensor starts the pump at reduced capacity, then, depending on volume of outflow the bottom sensor turns the pump up to maximum capacity to refill the tank.

I don't have a frickin clue, but this sounded good when it bounced off the wall.

Actually, I can't think of a single reason why a competent engineer, when looking at the configuration couldn't figure it out on his own. Can you?

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#6

Re: electrode sensor

10/19/2014 3:16 AM

I have installed this type of system before , the long rod is the common , the middle is pump start and the short rod is pump stop

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#7
In reply to #6

Re: electrode sensor

10/19/2014 3:30 AM

Can I know what is the common long rod for ?

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#8
In reply to #7

Re: electrode sensor

10/19/2014 6:52 AM

See #2

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#9
In reply to #8

Re: electrode sensor

10/19/2014 8:59 PM

A system that uses rods or electrodes such as these, relies on the very low current flow between the electrodes. In the control cabinet you will see a voltage-sensing relay that is wired to these electrodes, and then its contacts control the pump starting and stopping.

Some of the replies to the original question are assuming that each of the three sensors is an independent unit (two wires to it and some form of switching or sensing action that is done within that unit only). If you have single wires to each of the three rods or electrodes, then JohnDG is right-on.

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#11
In reply to #7

Re: electrode sensor

10/20/2014 5:08 AM

I would expect it's what's often called an earth rod, it completes a circuit with each of the other rods. In normal operation it is always submerged as level goes between middle (start) rod and short (stop) rod.

But we'd need more details of your set-up to be sure.

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#10

Re: Electrode Sensor

10/20/2014 1:27 AM

In our automatic level control applications we used the top sensor for sensing the high ('FILLED') level and is for stopping the filling operation. The middle sensor senses the 'REFILL' level and actuates the filling pump. Thus the level is all the time maintained between the top and the middle sensors. For some reason if the adequate filling does not take place then the level may drop below the lowest sensor. This actuates the "LOW LEVEL' alarm and will help initiate the appropriate 'low level' safety actions. Each sensor had a relay associated with it to help appropriate indications and control actions.

Regards

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