Pressure Gauge

Take a look here http://msl.irl.cri.nz/training_&_resources/Technical_guides/TG13.pdf

http://www.google.co.uk/search?sourceid=navclient-menuext&ie=UTF-8&q=calibrate+a+pressure+gauge

There are many places that do this. It is probably cheaper than doing it yourself.

To do it yourself you would need either a master that is occasionally sent away to be calibrated or a dead weight tester. Dead weight testers cost about $2000. They don't have to be calibrated.

You must also check the span as well as one specific pressure point. The gauge may be accurate at midrange or elsewhere and off at other points.

Note. Don't assume that new gauges are accurate. Many times they aren't. I saw one that actually had the pointer pegged on the wrong side of the stop.