20+ hours banging head off wall

[bowlingo]

Hi all,



I am trying to get a PH-CF transmitter to work with SMS controllers analogue inputs..



Here is the transmitter

http://www.omega.co.uk/ppt/pptsc.asp?ref=CDTX300

As you can see the transmitter takes the value of the PH and CF and then outputs them at between 4 - 20mA I can calibrate the system without problem using a multimeter i.e 5mS (half of CF range) = 12mA (half way between 4 and 20 mA)

They work great on there own i.e the PH side into the sms controller that is going to read the PH values or the CF side of the transmitter into the sms controller that is going to read Cf values....Until I have both on at once..when this happens the readings go crazy that the controllers read of which is due to them sharing the supplies in some fashion.

Here is the diagram provided by the company who sold me the transmitter

I have wired it exact and always the readings go crazy at the sms controller (but perfectly fine when wiring one or the other)

Here is the circuit diagrams provided with the transmitter

I have wired it in both combinations and used 3 x individual power supplies but no luck. You will notice the negatives are joined internally...I have opened the unit to confirm this. This means theres no way of seperating the supply apart from cutting the tracks inside the unit or similar. Due to the nature and affordability of this unit I am stuck with this one as I cant find anymore specific to my application that are not 3+ times the price.

On the website I bought the transmitter from you will see this...

http://www.omega.co.uk/ppt/pptsc.asp?ref=CCT

This is a loop isolator..if all else fails with the wiring could this or something similar work?

Thanks

 

[bowlingo]

Someone from another forum has just posted me this edit diagram...see the difference at the MA1 and MA2 points (connected to negative)

This isnt quite right as I know the power supplies negative is connected to the 0 terminals internally of which can be seen in the diagram that came with it I have also taken the unit apart and seen the track going between the power supplies - pin and the 0 pins

Can anyone take a look at this and give me there opinion before I got wiring it up and damaging a lot of moneys worth of kit?

Thanks

 

[bowlingo]

Anyone any ideas on this?

 

[shrtrnd]

My first idea, is to contact OMEGA, they've got a staff who helps with their products.
I'd do that before I did anything else.
My second idea, is questioning if your panel meters are somehow being daisy-chained
when you energize both of them at the same time.
Take a close look at the wiring of your panel meters, to make sure they're not
interfering with each other when your transmitter is activating the both of them.

 

[jackorocko]

I would contact omega through email with the drawing of schematic the person gave to you when selling the units. Tell them this is what you have and the issue. They should immediately be able to tell you what the issue is.

I think you will find it hard to get an answer here(or anywhere) unless someone has experience with such a system.

 

[bowlingo]

Hi...

I have been on the phone to Omega technical today and someone else and they are saying the input on the 2 x sms controllers are not isolated inputs of which is causing the 2 x seperate sms controllers to interfere with themselves possibly through the negatives. They have told me to try a loop isolator on each input of which will make floating inputs as I understand it.

I have found these

http://uk.rs-online.com/web/p/produ...552267573743D343636323231342677633D4E4F4E4526

http://docs-europe.electrocomponents.com/webdocs/03b8/0900766b803b8ed4.pdf

Maybe I can get away with using one as they are very expensive

Does this make sense?

Thanks

 

[bowlingo]

both types clip onto the standard 35.5 mm din rail.



the weimuller is thinner...and looks more like a weidmuller wire terminal block, whereas the RS looks like a module.

Terminal Blocks | www.weidmuller.com

I have just noticed the weimuller has an input range of max 15 volts..I am using a 24V power supply to power the transmitter.



please can you look at the 2 and tell me if theres going to be an issue with a 24V supply...



http://docs-europe.electrocomponents.com/webdocs/03b8/0900766b803b8ed4.pdf



http://docs-europe.electrocomponents.com/webdocs/0d57/0900766b80d575b0.pdf



the weidmuller is the MCZCCC



Thanks