TB 9-6670-254-50
NOTE
Balance (A2) should not be used for direct weighing of lower
class weights (Class C, Q, and T) with a minimum tolerance
value better than 18 mg, if a four-to-one accuracy ratio is
desired.
d. Balance (A2) is to be used, when performing the double substitution method, for
weights up to 5000 grams (11 pounds) which have a tolerance above 4.5 mg. Balance (A1)
is to be used for weights above 5000 g. Balance (A3) is to be used for weights which have a
tolerance of 0.3 to 4.5 mg. Balance (A3) should not be used for calibration of weights which
have a tolerance of less than 0.3 mg.
e. Class C, Q, and T weights may be calibrated by the direct weighing method (without
comparison to standard weight), using balance (A2), provided it has been calibrated and
minimum tolerance exceeds 18 mg (see note above). Paragraph 13 provides the procedure
for calibrating the balance.
8. Direct Weighing -
Double Pan
Balance
a. Performance Check
NOTE
Balance (A1 or A3) must be arrested before placing or removing
weights. Balance (A2) must be arrested before changing the
100g or 1 kg knobs.
(1) Place TI on left pan of appropriate balance, depending on value of weight being
measured.
(2) Place standard weight of nominal value (appropriate weight set (A5 through
A11), if possible, on right pan of balance. Pans should be near balance.
NOTE
Balances (A1 and A3) are not equipped with dampening
mechanisms. The pan arrestment handles may be used to
manually dampen balance as much as possible to decrease
settling time to equilibrium. Small, approximately equal,
oscillations on both sides of scale can be considered as an
equilibrium position.
(3) Place incremental weights from appropriate standard weight set, on lighter pan
(4) Transpose just the standard weight and TI, keeping incremental weight on same
pan as before. As necessary, add additional incremental weight to lighter pan to