Basically, it's best to have the manufacturer calibrate it for they know the zero and span adjustment of the component but if you know someone(preferrably a friend) with an electrical/electronic/control engineering background, with a master gauge, compressed air source, a multimeter, and possibly a current simulator, he could easily calibrate that at a cost of a burger,hehe If it still works but out of range, it can be fixed.
Im here in Dubai, dont know where in Australia you could find that someone aside from the maker, sorry.
Goodluck though, mate.