Sears carries a number of measuring calipers that could greatly assist with measuring your chain adjuster. They range in price from around $7 for the pocket job or over a $100 for a pro digital model with metric dial ones that fall somewhere in between. Have a look at Sears.com and search under "calipers"
Of course there is also the laserline method between the front and rear wheel axels OR a string plumb if you don't have the laser.
