| | | To assist setting up the wavelength positions there is a real time adjustment option. If this is set to ON, the grating and slits are set to the positions shown on the display and the selected wavelength will be output from the monochromator. This setting also generates the timing signals required for our photometry modules, allowing the effect of changing the individual parameters on system output signals to be monitored. If this setting is OFF, the slits are fully closed to prevent any unnecessary illumination of the sample, and timing signals are not generated. Each wavelength position to be utilised during a particular experiment needs to be set for inclusion in the wavelength program. This is done via option 7, and allows easy inclusion or exclusion of individual positions depending on the nature of the experiment being carried out. To review the current program settings and see which positions are included in the program use option 9, which will give you a display similar to that shown above. | | |
| | | 2. Show wavelengths and times Function 2 on the main menu leads to this sub-menu, where more detailed information about the program position settings can be obtained. The facility for the display of the actual slit widths used for a given position (Option 3) allows users with manual slit adjustment to set the most appropriate setting for a given experiment. The same mechanical slit width will not apply for all positions, as the relationship between mechanical slit width and optical bandwidth is somewhat wavelength dependent. The information here will allow the micrometer to be set to the best compromise. A facility that is potentially very useful under ALL circumstances is option 4, "Show optical bandpass profiles", as it allows the actual bandpass characteristics for each position to be displayed. This is particularly valuable when experimenting with different input and exit slit widths. A very important guide is that the optical throughput at each position is proportional to the area enclosed by the bandpass characteristic. In general, for maximum throughput the input and exit slit widths (defined optically, as we do, rather than mechanically) should be the same. The bandpass characteristic is then triangular, with the bandwidth, as defined between the 50% points (full width half maximum, FWHM), being half the total width of the spectrum along its baseline. This topic is well described in the theoretical part of the technical manual, so for more information, please read that section. | | |