Ametek Land 4500 MKIII, User Manual

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F - 1
Model 4500 MkIII Opacity and Dust Monitor
User Guide
F
Changing the Installation Pathlength on a Model 4500 MkIII
F1 Set the correct focus
The Transceiver focus and retro reflector must be set according to the
instrument’s specified flange-to-flange path length. Refer to the focus table
(Section F5) for the correct focus spacer setting.
1) Remove the main lens assembly by undoing the three fixing screws.
2) Remove the screws. Remove the lens retaining plate by turning it
clockwise.
3) Carefully remove the spacers, O-ring, lens and more spacers.
4) Look up the flange-to-flange path length in Section F5. Find the row
where the pathlength lies between the values in the minimum and
maximum columns.
5) Make a note of the Lens Spacers and the Reflector Part Number.
6) The complete set of spacers contains two of each size: 8, 4, 2 and 1
mm. Select spacers which add up to the value in the table e.g. 18 = 8
+ 8 + 2. Put these spacers into the lens holder. Insert the lens (flat side
down), then the O-ring and finally the remaining spacers.
7) Replace the retaining plate and lock by pressing down an turning anti-
clockwise. Check that all three screw holes are open. If not, remove and
reposition the plate.
8) Replace the lens holder in the Transceiver and tighten the three
screws .
F2 Align and Calibrate the Model 4500 MkIII
The following must be done in a laboratory or a clean workshop. A test
kit comprising tabletop stands and power supply available from Land
instruments and make the procedure more convenient.
1) Optically align the Model 4500 MkIII
2) Perform a clear stack calibration using the Recalibrate function. Verify
that the instrument reads 0% opacity on a clear path and 100% opacity
when the beam is blocked.
F3 Set the B constant
Check the B (balance) value using the Calibration: Manual Cal function. The
B (balance) value must be within the range of 0.95 to 1.05. If the value is
outside this range, carry out the following procedure to choose new aperture
and grating plates.
1) Remove the Zero Reflector and disassemble as shown in Figure F-1.
Find the aperture and grid identifiers etched on the tabs and identify the
relevant sequence number.
2) If the B-value is too low, choose an aperture and grid with a sequence
number greater than the current value. If the B-value is too high,
choose an aperture and with a sequence number greater than the
current value. Each sequence number corresponds to approximately
0,05 difference in the B-value.