but is that the pH instead of the concentration of the acid...
you could work out the [H+] from the pH but is that the same as the actual concentration of the acid, as in molarity?
Ok to determine concentration of acetic acid in vinegar you titrate the vinegar with a strong standard base (like NaOH). Instead of using an indicator however, use a data logger with a pH attachment. Set the logger to do frequent pH checks, and perform the titration (no indicator) until it's gone way past the equivalence point. Now on the graph of pH vs solution added, the equivalence pt will be where the gradient is steepest.