Weighing by Double Substitution Using an Equal Arm Balance

1 Page 1 SOP No. 3 Recommended Standard Operations Procedure for Weighing by Double Substitution Using an Equal-Arm Balance I. Introduc tion I. i . Purpose The double substitution procedure is one in which a standard and an unkno... Open at page → 2 Page 2 the standard and test weights as well as a determination of the sensitivity of the balance under the load conditions. All weighings are made at regularly spaced time intervals to average out any effects due to linear ins... Open at page → 3 Page 3 2.5. Procedure 2.5. I. Preliminary Procedure Conduct preliminary measurements (without recording data) to determine the values for T, ts ' tx, and sw for use in measurement procedures, 2.5.2, or 2.5.3. This will serve to... Open at page → 4 Page 4 2.5.2.4. Observation 4. Remove weight X and tx and replace with Sand ts. Weight sw remains on the balance pan. Record the sum of the turning points and the time. 2.5.2.5. Calculate the time intervals between the successi... Open at page → 5 Page 5 3.2.2. Air Buoyancy Correction 3.2.2.1. Calculate the air density, PA' as described in section 8 of the Appendix to SOP No. 2 or obtain from Table 9.9. 3.2.2.2. Calculate the mass Mx of the test weight X and its mass cor... Open at page → 6 Page 6 3.2.2.4.2 . Apparent mass versus brass 1 - .0012 Px AM vs brass - Mx .999857 4. Assignent of Uncertainty The limits of uncertainty, U, include estimtes of the uncertainty of the mass standards used, Us' plus th~ uncertai... Open at page → 7 Page 7 Appendix Double Substitution Data Sheet for Equal-Arm Balance (Option A) Test No.: Sheet No.: Date: Item Identification: Balance: Standard Identification: Observer: Temperature: Pressure: Re1. Hum.: , Cs (Cs)- ~ AMsw(Msw... Open at page → 8 Page 8 Appendix Double Substitution Data Sheet. for Equal-Arm Balance (Option B) Test No. : Sheet No. : Date: Item Identification: Balance: Standard Identification: Observer: Temperature: Pressure: Re1. Hum.: , Cs(Cs)- ~ AKsw(M... Open at page → 9 Page 9 Appendix Double Substitution Data Sheet for Equal-Arm Balance (Option A) Test No.: 137 Sheet No.: 1 Date: 8/27 /86 Item Identification: 1000 lbNo.623 Balance:Russell Standard Identification: #11and #22 Observer: HO Tempe... Open at page → 10 Page 10 Pa - 1.163 mg/cm3 - 0.001163 g/cm3 MS(l Mx . PA) ( PA ) ( PA ) (0i-01+03-04) -- +Mt 1-- -Mt 1-- + Ps S Pts x Ptx 2 PA MSW(l - ~) Psw . 03 -02 1 r (.001163) ( Mx -rOOO.0047 1 - 8.0 + 3.625 1- Px .001163) _ 3.642 (1 _ .001... Open at page →