Thanks...
The ph and conductivity transmitter is a dual output unit each of the 2 wires on the outputs goes to an individual sms controller connected between AGD and 1 (analogue inputs)
Only when I try to connect both sms controllers up at once do I get the problem..on there own they are working perfect
When I connect a multimeter across the PH output and the CF output (using 2 multimeters) the readings are perfect but when I put them into the sms controllers (remember there is 2 inside the system I have built) the readings go all over the place which must be to do with the 2 sms controllers sharing a common point..possibly negatives although ive tried 2 x power supplies but to really be sure I need to strip the entire system down of which could take me many hours as there could be a relay or something sharing a negative.
Last night I got the CF probe to work as it should with the ph wired up also by changing the base and scale settings within the sms controllers software..although a bit rough it worked well. Then I tried to calibrate the PH side by putting the probe into PH 7 buffer solution (it was in PH 4 buffer solution when I was calibrating the Cf side) what happened when I put the PH probe into PH 7 is the CF went from 0 (free air as it should be) to 2.43! This means dependant on what one probe is doing effects the other of which must be to do with the shared point between the 2 sms controllers...
I have just found these..
http://uk.rs-online.com/web/p/produ...552267573743D343636323231342677633D4E4F4E4526
http://docs-europe.electrocomponents.com/webdocs/03b8/0900766b803b8ed4.pdf
These will isolate the outputs from the transmitter so they will be floating as I see it.
Do you think this will work?..Although the sms controllers are still joined in some way..I cant picture in my head or by drawing if a circuit is being made up?
Due to the cost of these isolators I am hoping I can get away with using one then send the second one back as a return (RS are good for returns)
Thanks
Alex
The ph and conductivity transmitter is a dual output unit each of the 2 wires on the outputs goes to an individual sms controller connected between AGD and 1 (analogue inputs)
Only when I try to connect both sms controllers up at once do I get the problem..on there own they are working perfect
When I connect a multimeter across the PH output and the CF output (using 2 multimeters) the readings are perfect but when I put them into the sms controllers (remember there is 2 inside the system I have built) the readings go all over the place which must be to do with the 2 sms controllers sharing a common point..possibly negatives although ive tried 2 x power supplies but to really be sure I need to strip the entire system down of which could take me many hours as there could be a relay or something sharing a negative.
Last night I got the CF probe to work as it should with the ph wired up also by changing the base and scale settings within the sms controllers software..although a bit rough it worked well. Then I tried to calibrate the PH side by putting the probe into PH 7 buffer solution (it was in PH 4 buffer solution when I was calibrating the Cf side) what happened when I put the PH probe into PH 7 is the CF went from 0 (free air as it should be) to 2.43! This means dependant on what one probe is doing effects the other of which must be to do with the shared point between the 2 sms controllers...
I have just found these..
http://uk.rs-online.com/web/p/produ...552267573743D343636323231342677633D4E4F4E4526
http://docs-europe.electrocomponents.com/webdocs/03b8/0900766b803b8ed4.pdf
These will isolate the outputs from the transmitter so they will be floating as I see it.
Do you think this will work?..Although the sms controllers are still joined in some way..I cant picture in my head or by drawing if a circuit is being made up?
Due to the cost of these isolators I am hoping I can get away with using one then send the second one back as a return (RS are good for returns)
Thanks
Alex