Buchi C-640, Operation Manual

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3 Technical data
16
C-640 Operation Manual, Version C
3 .6 Signals and parameters
3 .6 .1 Light intensity
The light intensity of a newly installed lamp used with the test cell is set to 100% on all wavelengths.
These values form the reference for later tests of the light intensity.
3 .6 .2 Range of wavelength
The wavelength range of the detector C-640 depends on the assembly of the optical parts, the
calibration results and the number of elements of the CCD sensor that are used at the same time for
processing (“electronic half width of wavelength”)
The default electronic half width of wavelength (HF = 4) results in a wavelength range from 200 to 840
nm. Increasing of the electronic half width of wavelength (HF) can decrease the wavelength range
(symmetric for both sides of the spectrum).
3 .6 .3 Optical and electronical half width – spectral resolution
The base spectral resolution of the detector is based on the placement of each element of the CCD
sensor according to the placement of the lamp spectrum and the slit width. It is about 0.85 nm per
element while the slit width is a multiple of the size of one element. The slit width of the detector is 8 nm.
Multiple elements of the CCD sensor are used for signal processing at once. The total length of the
processing elements for one wavelength will affect the spectral resolution in a negative way. On the
other hand it will improve the dynamic range reduce the noise of the system. For these reasons the
adaption of the number of processing elements (“electronic half width of wavelength”) is optional
while the default value HF = 4 (8.4 nm) corresponds to the slit width and has a minimal effect on the
spectral resolution.
3 .6 .4 Time constant / data filtering
Processing of the raw absorbance signals is done according to the time constant of the detector.
Therefore a classic continuous time filtering is used. This kind of processing is done only for absor-
bance data but not for intensities or scanning of absorbance and intensities. For absorbance scans a
special low level time constant is used. Available values are 0.5 s, 0.75 s, 1.0 s and 2.0 s.
3 .6 .5 Analog range ratio
The available values are: 0.05 AU/V, 0.1 AU/V, 0.25 AU/V, 0.5 AU/V, 1 AU/V, 2 AU/V, 3 AU/V, and 5
AU/V.
3 .6 .6 Display brightness
The brightness of the display can be adapted to the following values:
12.5%, 25%, 37.5%, 50%, 62.5%, 75%, 87.5% and 100%.
3 .6 .7 Subscription / Remote or local control
Remote control means the device is controlled via the RS232 interface. Local control means the
detector is controlled using the keyboard and the graphical display of the detector itself.
Remote control starts immediately after the receipt of the first command via the RS232 interface and
is stopped after a time period of 4 seconds without any new command. For permanent remote control
a continuous communication with the detector (e.g. reading detector status) has to be established.
During subscription or remote control the instrument keyboard is locked but the graphical display still
shows the current measurement data.