Hi

First post here and from what I have read this will fall firmly into the "dumb question" category, but I need to get it sorted so here goes!

I have a rainwater collection tank in which I intend to install one of these - https://www.cynergy3.com/sites/default/files/ILLSU 2015.pdf (3-wire version) - to monitor the water level using a Crestron DIN-AP2 controller. Whilst I am confident of the wiring as it relates to the power and signal to the controller, I want to be sure that I understand how to earth this thing. The data sheet isn't the most helpful, stating that "care must been taken when screening and earthing".

Do I connect the screen and the ground (green & pink) cables to earth on the Crestron processor, or must the screen be earthed separately? Or am I missing the point by a million miles?

Some guidance would be very much appreciated!

 

It is best to only make on earth connection, and the best place would probably be at the controller. Using two earth connections invites ground loops that might be caused by other grounded equipment.

 

It is best to only make on earth connection, and the best place would probably be at the controller. Using two earth connections invites ground loops that might be caused by other grounded equipment.

Thank you for responding so quickly.

My intention is (/was) to connect the "Ground" from the sensor (Pink) to the controller (the I/O block has a common G for all the inputs). Are you suggesting that I simply leave the shield wire unconnected. Or, if I connect the shield to the controller, leave the ground unconnected?

 

I would connect both the shield and the ground return wire to earth at the controller, and leave the distant end of the shield floating.

 

This is where I really start to embarrass myself. The "distant" end of the shield is (isn't it?) connected to the sensor in the tank but I know enough to know that you don't mean floating in water )). My intention was to connect the cable from the sensor to a piece of cat6 in a junction box inside the top of the tank and from there about 30m underground to the controller. At the controller there would then be both the ground and shield cables which I can, of course, both connect to G on the I/O block. I am probably asking a circular question, but if I connect both to the controller, what I am leaving floating?

I could of course just wire things up and see what happens, but these sensors ain't cheap and Crestron controllers far less so, hence the caution.

 

You understand correctly.

The sensor end of the shield is not grounded -I call that floating. It is unfortunate that the term was used in the discussion of water level sensing.

 

Thank you, I believe I get it now.