c. Scale focusing in controlled by the long knurled knob (fig. 2-29) at the rear of the scale. Carefully adjust the
knob until the desired focus is achieved on the optical scale.
d. Zero point adjustment is accomplished by first rotating the weight control knobs and micrometer drum knob until
the macro weight scale and optical scale are returned to zero. Move the arrestment lever into PRE-WEIGHT position
and adjust the micro scale to zero by turning screw (1, fig. 2-30).
(1) Range adjustment of the zero control knob has the effect of recentering the knob. Set the knob in the
center of its adjusting range without regard to micro scale reading. Arrest the beam by moving the arrestment lever to
horizontal position. Remove the balance hood and adjust the knurled knob (6, fig. 2-30) until optical and micro scales
are zeroed. If the scale deviation is so great that this method cannot be used to zero the knob midrange, it is necessary
to zero the macro system as described in (6) below.
(2) To perform macro zero adjustments, check zero calibration as described in (d) above; then arrest the
beam and remove the hood. Loosen the locking screw or knurled screw (2, fig. 2-30), and adjust the scale by turning the
knurled screw as required to zero the macro scale. Retighten the locking screw, release the beam, and check zero
again. Repeat the correction if the deviation exceeds one scale division. As soon as the deviation is reduced to one
scale division, replace the hood and use the zero control knob to adjust to zero.
(3) Check sensitivity by rotating the weight control knobs until 01 appears on the macro scale while the beam
is arrested. Place a 1-g weight on the pan, release the beam, and check zero on the optical scales as described in (d)
above. Rotate the weight control knobs to show zero on the macro scale. Let the optical scale swing in and read the
result. If the full deflection of 0100 is not obtained, adjust the sensitivity by turning the knurled nut (3, figure 2-30) to
adjust the scale accordingly.
Turn weight control knob so that 01 appears on the macro scale and set zero point as described in (4) above. Recheck
the sensitivity. If required, readjust the sensitivity, set the zeropoint, and recheck. Continue the sequence until the
balance is correctly adjusted.