Attenuation; Figure 3-5. Dg-4/5 Output Attenuation; Figure 3-6. Log Of Attenuation Vs. Change In Output Galvanometer Value - Sutter Instrument Lambda DG-4 Operation Manual

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Figure 3-5. DG-4/5 output attenuation.

3.7.7.3 Attenuation

If the Output Galvanometer value is either slightly increased or decreased from the value
that produces the peak output, the light coupled into the light guide will decrease as
schematically depicted in the figure on the following page. The nominal relationship between
galvanometer value and output is shown in the plot below. The exact relationship may vary
from unit to unit and filter position to filter position. The actual attenuation produced must
be determined by the user. The degree of attenuation produced by increasing the
galvanometer value is similar to that produced by an equivalent decrease. Remember, though,
that you are limited to an overall range of 0 to 4095. If the output galvanometer value for
maximum output is already within 1000 units of a limit (0 or 4095) it is logical to attenuate
by changing the value in the direction that moves away from that limit. This method is very
useful for attenuating output by less than 1 log unit. It is recommended that you use neutral
density filters when attenuation of 1 log unit or more is desired.

Figure 3-6. Log of attenuation vs. change in output galvanometer value.

LAMBDA DG-4 & DG-5 OPERATION MANUAL – REV. 3.05C (20150414)