[Code of Federal Regulations] [Title 40, Volume 31] [Revised as of July 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR1065.290] [Page 710] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents Subpart C_Measurement Instruments Sec. 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 Sec. 1065.205. Note that your balance-based system must meet the linearity verification in Sec. 1065.307. If the balance uses internal calibration weights for routine spanning and linearity verifications, the calibration weights must meet the specifications in Sec. 1065.790. While you may also use an inertial balance to measure PM, as described in Sec. 1065.295, use a reference procedure based on a gravimetric balance for comparison with any proposed alternate measurement procedure under Sec. 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 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.