Section 1065.290 - PM gravimetric balance(a)Application. Use a balance to weigh net PM on a sample medium for laboratory testing.(b)Component requirements. We recommend that you use a balance that meets the specifications in Table 1 of § 1065.205 . Note that your balance-based system must meet the linearity verification in § 1065.307 . If the balance uses internal calibration weights for routine spanning and the weights do not meet the specifications in § 1065.790 , the weights must be verified independently with external calibration weights meeting the requirements of § 1065.790 . While you may also use an inertial balance to measure PM, as described in § 1065.295 , use a reference procedure based on a gravimetric balance for comparison with any proposed alternate measurement procedure under § 1065.10 .(c)Pan design. We recommend that you use a balance pan designed to minimize corner loading of the balance, as follows: (1) Use a pan that centers the PM sample media (such as a filter) on the weighing pan. For example, use a pan in the shape of a cross that has upswept tips that center the PM sample media on the pan.(2) Use a pan that positions the PM sample as low as possible.(d)Balance configuration. Configure the balance for optimum settling time and stability at your location. 73 FR 37300 , June 30, 2008, as amended at 75 FR 68462 , Nov. 8, 2010