HAMAR LASER STEALTH Series, General Training Manual

Page: 103 / 113

99
Adjusting the Vertical Trimpot
1. Manually center and square the target to the oncoming laser beam
Make sure that the target is mounted in the target stand with the cable hanging down from the lowest
(6 o'clock position) on the target.
2. Mechanically center target with the micrometers on the target stand
Adjust the vertical axis first by turning the micrometer on the target stand until the vertical readout
display window reads 0.000. Be sure to center in such a way as to remove the micrometer backlash
(turn the micrometer dial beyond and then back to the desired measurement). Complete the
mechanical centering by adjusting the horizontal axis micrometer control until the remaining readout
display (R-307) reads 0.000.
3. Read and record the micrometer settings (not the readout display)
Once the readout displays 0.000 (both windows on the R-307) the corresponding micrometer settings
should be noted on a worksheet.
4. Turn the vertical axis micr.025 in. (one full turn)
Turn the Vertical axis micrometer control one full revolution (+.025 in.). Be sure to eliminate
micrometer backlash.
5. Adjust the Master Gain (Vertical Input Trim Screw)
While watching the numbers in the vertical window of a readout, use a small, flat-head screwdriver to
adjust the set of the Master Gain (vertical input trim screw). Turn the screw until the vertical window
on the readout reads
25.0
.
6. Re-zero the Vertical axis control Micrometer
Reset the Vertical Axis Control Micrometer until the display reads 00.0.
7. Adjust the Master Gain (Vertical Input Trim Screw)
If the readout display shows -25.4 for a micrometer move of -.025 in., adjust the Master Input
Trimpot until the readout reads (-25.4 + -.2) = -25.2. While watching the numbers in the vertical
window of a readout, change the set of the Master Gain (vertical input trim screw) with the
screwdriver. To trim out half of the difference between the displayed move and the micrometer move,
adjust the trimpot so that the numbers in the vertical display read out with half of the error removed.
Adjusting the -25.4 display reading to -25.2 trims out half the error on the readout display for an -.025
micrometer move.
8. Re-zero the Vertical Micrometer
Reset the Vertical Axis Control Micrometer until the display reads 00.0. Calibration of an R-308
Readout is complete when numbers on the readout windows fall within 5 percent of corresponding
micrometer moves.
9. Close the R-308 Readout housing and tighten all screws. Review results.
If you would like to see the effect of the calibration trimpot adjustments, recheck the V+ reading with
a +.025 in. micrometer turn. You will notice that the display will not register as e.025 in.
When you recheck the vertical readout window with a +.025 in. micrometer move, the number 24.8
will be displayed in the vertical window of the readout. In this example, you have read -25.4 for a -
.025 in. vertical micrometer move, adjusted the trimpot Master Input gain and "split" the difference.
Trimming out the entire V+ reading error eliminates the major difference between the micrometer
move and the readout display. During the V- adjustment of the calibration trimpot, the remainder of
the vertical axis calibration error is removed by changing the span to balance the V+ and V- readout
error. After adjustment, the readout display will show a smaller amount of error for both V+ and V-
readings.
Any target readings will now have an integral 0.8 percent error. If you are aligned within .001 in., the
integral readout calibration error will mean that the alignment is within .001 in. ± 8 micro in. (8 millionths
of an in,).
Note: Follow this procedure to calibrate a readout as perfectly as is possible with an analog electronic device.