To insure the success of your mastering procedure and the stability of the gage, the set points
should be re-checked with the masters at frequent intervals. The need for constant mastering will
decrease as the Trendsetter™ and the gage demonstrate stability and repeatability. Frequent mas-
tering will ensure that there are no loose contacts, and that the system is not experiencing any drift.
These potential failures can be found only by frequent mastering under production conditions.
2-1.5 Main Magnification Adjustment
At the lower back of the column is an inspection panel held in position with two screws. Removal of
this panel will expose calibration trim pot screws labeled Cal. A and Cal. B. Each input should be
set independently, using some basic measuring means such as a micrometer drive, gage blocks, or
if a single probe is being used in the fixture, this may be used with the master or with shims. Switch
to Channel A on the front of the column and set probe A to its low limit. Adjust the front zero knob
to the low column reading.
Move the probe tip the mastering distance by one of the described methods and turn the Cal. A pot
to bring the column reading to the high position. Re-check, and if, necessary, repeat between mas-
ter points to obtain the desired column movement between min. and max. master positions.
Repeat this procedure for probe B with the front panel switch turned to Channel B. With both A & B
set for magnification, replace the rear inspection panel. If both probes are being used as A & B, turn
to Channel AB and do any final master trimming on the front pot as previously described.
2-1.6 Balance
One final word on calibration is the concept of balance. Balance is the final “trimming out” of all
system magnification errors. It should be noted that balance only concerns differential measure-
ments; when both probes are measuring a diameter for example. Also, lack of balance is one of the
chief causes of poor system repeatability.
Balance is easily achieved and observed by the use of a simple mechanical balancing fixture. The
fixture clamps the A and B probes in opposing positions, and with the use of a micrometer, moves
the probes in exactly equal, but opposite directions. Such a fixture is available through Edmunds
Gages as BG29412. To check balance, complete the calibrations as described in the previous sec-
tions. Mount the A and B probes in the balancing fixture. Adjust each probe to its mechanical zero
as observed on the Trendsetter™ bargraph display. Then with the range switch set to desired appli-
cation range, and the polarity/function switches set to A+B mode, rotate the micrometer head
some convenient distance. This distance should not exceed 2x the selected range. Observe the
bargraph, it should remain fixed at zero under these conditions. If, for example, the Trendsetter™ is
set to the 0.005 inch range and the micrometer head is rotated thru 0.010 inch, the bargraph should
remain exactly at its zero position. Any movement observed on the scale indicates the system is
out of balance.
To achieve balance, a magnification adjustment is required to one channel only. First, reset the sys-
tem back to its zero starting point. Next, offset the micrometer head and adjust the B channel mag
through the rear cover. The initial amount of adjustment should be small, say no more than 1/4 turn
on the B mag pot.
Observe the bargraph, did the error get greater or smaller? If greater, turn the mag pot in the oppo-
site direction. If smaller, adjust the pot in the same direction until the bargraph remains on zero, with
the micrometer rotated thru its range. To achieve a greater degree of balance, increase the systems
sensitivity via the range switch. With a little practice and patience, balances in the order of 25
microinches or less are easily obtained!
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