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The Ortofon Stylus gauge is a very simple tool to enable you to set your stylus tracking pressure correctly. This is really important to get secure tracking and prevent damage to your records. Unfortunately the stylus pressure dials on many tonearms are notoriously inaccurate.

The range is from 0.8gm to 3gm.  The scale is make in milli-Newtons which are approximately 0.1gm. So 15 is 1.5gm. 

To use, sit the gauge on top of the platter and place the tip of the cartridge's stylus on the long number sire of the beam balance. Let's say you position it at the 15 mark. If the short side of the balance (with the word Ortofon on it) remains below the sides of the plastic pivot piece then you cartridge is  exerting less than 1.5gm downforce. If the long arm goes down and the short arm is higher than the sides of the plastic pivot piece then the downforce is more than 1.5gm. If you adjust the counterweight position so that the beam balance is horizontal then you'll have 1.5gm downforce. For 1.75 gm position the stylus about halfway between the 15 and 20 markings.