Usually your stanchion will be mounted on some form of grid work or grating - this is earthed, therefore your stanchion is earthed. I would think that if it were mounted on concrete for example - that you would want to take it to your earth. Just bear in mind that the earth that you take it to should ultimately be the same earth as your power supply. I.e. If you come from the mains with your AC voltage you want your earth mat connected to the neutral (star point) of your transformer. This will prevent you having problems with floating earths and such like problems.