Two wire digital level sensor

[Jothiswarup]

Hi guys,

Just need a sanity check because I am told the sensor wired recently is not working properly.

Sensor - Carlo Gavazzi VN1
Sensor controller - Carlo Gavazzi CLP2EB1B230

The sensor is just one probe and it has two wires (Black and Grey). I wired the black, which is the reference, to sensor controller terminal 7 which in turn is grounded and grey to terminal 5 and jumper terminal 5 and terminal 6.

All it does is give a digital signal when the water reaches the probe. Very basic but I am told there are false signals so is there anything I did wrong?

Attached are specs and rough drawing showing wiring. Sorry, do not have CAD.

 

[willxfmr]

Looks to me like you have it wired right, assuming you are measuring the level in a conductive vessle. My only thought would be, did you use a shieled cable the whole way? Also don't discount a bad device. Sometimes "new" and "working" aren't one in the same.

Will

 

[nonuke]

It is important to know the value for the water conductivity. If the value is very low, you can´t use conductivity probes as level probes.

 

[Jothiswarup]

Thanks for the reply guys. No it's not a shielded cable but sensor has water tight housing and came with 2m cable. Apparently one of the operators messed with the sensitivity and Full/Empty adjustment causing this issue. I got that answer after drilling them with questions. It's all good now. Appreciate your responses very much!

 

[Aabeck]

I work on a similar setup in a sump pit.

I have found the module is very susceptible to moisture anywhere in the wiring of the probes (senses full when the moisture shorts across the wires). The operators frequently hose down the entire area, getting the probe mount & cabling wet

Also one customer I have I tried to troubleshoot two applications with similar setups & found the problem to be the water - the probes were put in tanks filled with RO/DI (Reverse Osmosis/De-Ionized water) that had no metal content & thus no conductivity; could not use probes in those applications.

 

[Jothiswarup]

Should I wire the drumscreen to terminal #7 on the controller as well? Right now the terminal #7 is only grounded inside the electrical panel.

 

[Aabeck]

If by drumscreen, you mean a metal tank wall, I would say yes, that would help especially if the reference probe ever gets dirty or contaminated, which happens if the tank has anything other than pure(ish) water.

 

[Jothiswarup]

Yes it a metal tank. There is no additional reference probe/electrode. Level sensor only has one electrode with two wires (Black and gray).

I called the manufacturer and was told terminal #7 on the controller needs to be wired to the metal tank hence acting as reference.

What is the difference if #7 grounded in the electrical panel or wired to tank? Isn't still ground reference either way?

 

[Aabeck]

When you talk about grounds, there can be a voltage potential from one ground rod/point to another.

Years ago had a new machine with an Allen Bradley servo drive that the machine builder couldn't get operating reliably or consistently. Called in A-B servicemen & their conclusion was the control panel had a ground rod connected to it, but the machine frame was actually connected to the ground of the main stamping press & the servo controller was picking up the voltage difference as a ghost signal - had to run a daisy chain of ground wires from each point to all others & the problem went away. They called it ECM variance.

 

[nonuke]

If you are sure the tank has the same ground as the electrical panel, you don´t need to connect the black wire to pin 7 of the level relay. Just connect pin 7 to the electrical panel ground. I do this all the tyme with the same type of level relay. If you have a pump connected to the tank by a steel or SS pipe, you already have your ground.

 

[GlenGineer]

I'm not familiar with this particular level sensor but I have designed the level control for several wash lines. Often on wash lines the problem is controlling foam. Soap carryover in rinse tanks foams up really bad. If the mechanical system that the electrical switch is in is not properly designed the level sensor will be exposed to foam and give false positives.