I have an application to control a swimming pool which is essentially a chemical process. Following is a description of what I want to be able to do: 1. Input 2 items via a control panel and read 3 probes-pH, water temp, and orp(oxidation, reduction potential-used for determining chlorine requirement). The input signals will be mV up to 1000mV. 2. The PLC needs to then do an algebraic calculation. 3. Based upon that number an "IF, Then" statement is required. 4. Another simple algebraic addition is then done 5. Another "IF, Then" statement which either sends a signal to a relay or stops sending a signal to a relay. I need a recommendation for a simple PLC which is inexpensive that I can program to do this job. I have zero experience programming PLC's and if necessary can outsource this work although I am an ME with some scientific language programming experience. If someone could point me in the right direction, I would appreciate it. So far the only PLC I have found that will do this is a Panasonic AFPE224300 which can do floating point calculations but the control inputs must be between 21-24 volts and mine are from probes and will be much lower. Thanks in advance. Pat Thomas Tucson, AZ
