water testing

hello all

I just thought that I would ask a simple question.

is there any plc out ther that can monitor the ph of water,the water alkalinity, and the calcium levels in the water, i can prog. the temperature, the rest is a mystery to me.
I am using this on a reef aquarium that I have been asked to automate for a customer of mine. I have not started as of yet,I am still in the development stages of the project!
Also if this can be done what is the type of signal Eg. 4-20ma.?

Would this be cheaper?

I'm sure you could use a PLC for your application, but something like this would probably be cheaper.

http://www.neptunesys.com/

Ph Probe

HoneyWell makes a ph probe that constantly monitors the ph level of your liquid. We used these in our Waste Water treatment plant. They are very reliable but they are somewhat expensive. They use a 4-20mA signal that is supplied by a HoneyWell controller. As far as monitoring calcium levels I'm not sure of anything, but there probably is something out there.

Rosemont and Foxboro both have what you need. I like Foxboro, there probe is better in my opinion. beerchug

I don't think you problem is what PLC to use as the replies you have already gotten show it's much more of what kind of sensors to use and where to get them.

I've had good success with the sensors from this company:

http://www.analyticaltechnology.com

pH is easy, but alkalinity and calcium usually require some kind of near real time measurement with automatic titration and chemicals etc. I know ATI has some experience with aquaculture, so you might want to talk to them for some guidance. The sensors can either give you a 4-20 mA signal for a PLC analog input, or you can set alarm levels in the sensor and get a contact closure for a discrete input.