Know the total history of the hardware from support logs and lab calibration administrations.The tolerance test of the lab gears should be done before making a deal. Some of the main players in the market too can make fool of you by selling poorly calibrated lab equipment. Your entire business will shatter if the equipment your lab is using to produce profit turns out to be uncalibrated. There are many certified calibration service providers who are good and can help you with your quest of an effective used equipment.