PH stands for Parts Hydrogen and it is a measure of hydrogen ions.

I'm sure companies manufacture chlorine analyzers, however, I have never calibrated one. Maybe some one else on this list has and has more answers for you.

PH stands for Parts Hydrogen and it is a measure of hydrogen ions.

Not quite accurate. pH (Lower case p, upper case H) is the chemists shorthand for "The base 10 logarithm of the inverse of the concentration of Hydrogen ion in Moles per Liter) You can express any ion the same way. pCa would be "The base 10 logarithm of the inverse of the Calcium ion in Moles per Liter". It might be more appropriate to check the pCl, but that will not show free Chlorine dissolved in your solution, only that fraction of it that is dissociated into ions.

There are a number of things one can do if you want to relate chlorine and pH. For example: Cl2 + H2 = 2 HCl, which is an acid and has free H + ions in water. If you can determine the quantity of hydrogen (as by electrolysis of water and from the amount of current used), then you should be able to calculate the amount of HCl generated. You can then relate that to pH. If you just want to analyze for chlorine, there are a number of companies which manufature such equipment: Hach; Yokogawa; Kuntze sells analyzers for both free and total chlorine.

"what is the relationship between chlorine and PH? Free Chlorine measurement is affected by PH of water sample? How abt temp?"

Cl2 is an acidic gas; it will lower your pH. Likewise, the higher the water temperature, the lower the pH. For the rest of your questions, there are many different makes and models of chlorine analyzers. Your best bet would be to log into the manufacturers' websites and download their brochures and O&M manuals.