URGEnT: GeFanuc PLC series 90 program needed

Hello ppl,
I would really appreciate it if someone can send me a sample program for GeFanuc series 90 PLC. What I need to do is..I'm taking input from a pH electrode and if the pH reading is below a particular value say 8 , I want to switch a relay , if it goes above it i want to switch it off again! If you kant give me the sample program, atleast give me an idea how to do it.
Thanx, waiting for your reply,
SSS.

There are six relational instructions in the Series 90-30 function set. They are GT (Greater Than), GE (Greater Than or Equal To), LT, LE, EQ, and NE. They compare two numeric values and turn on or off a discrete bit depending on the results of the comparison. These will do what you need.

Your pH sensor will report a value to an analog input channel (%AI). The raw data from the analog channel may need to be scaled before using it in the comparison instruction. For example, maybe the pH sensor transmits a 4 - 20 mA signal to the analog input module such that 4 mA represents a pH of 2 and 20 mA represents a pH of 12. The raw data in the analog input corresponding to 4 mA is zero, while the raw data corresponding to 20 mA is 32000. You will need to perform some arithmetic to scale those raw data values to engineering units (pH).

Depending on which CPU model you have, you may be limited to performing arithmetic calculations on integers.

I hope this points you in the right direction.