Waters 2489, Обзор и руководство по обслуживанию

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June 11, 2015, 715004752 Rev. A
Page 59
– Maximum ratio: An actual ratio equal to the
maximum ratio results in a full-scale output of 2 V.
Absorbance offset is ignored with this selection.
For a RatioPlot, the actual voltage charted is
Volts out = 0 V if Absorbance A and B
<
minimum
AU
Volts out = (Absorbance ratio – minimum ratio) ×
2 V/(maximum ratio – minimum ratio)
To ensure proper operation of the RatioPlot
function, be sure the selected time constants for
both channels are set to the same value.
• Difference Plot (A-B) – Charts the difference in
absorbances at two different wavelengths. The
scaling for the difference plot is identical to the
Absorbance selection above, except that the
charted absorbance is the difference (subtracted)
in value of the two absorbances measured on the A
and B wavelengths. The detector uses the AUFS,
absorbance offset, and voltage offset of the
selected channel for scaling.
Volts out = Absorbance difference (A – B) ×
2 V/AUFS (of selected channel)
Filter time constant Adjusts the noise filter (time constant) to achieve the
optimum signal-to-noise ratio without changing the
sensitivity setting. See the discussion “Filtering noise”
on page 20 for more information.
Voltage offset Adjusts the charted analog output signal. Entered in
millivolts, this function adjusts the 2-V signal by the
entered value. This function is useful for making
minor adjustments and for rendering null any offset
between the detector and a connected external data
system.
Chart polarity Inverts the charted chromatogram. Entering the plus
sign (+) produces a normal chromatogram; entering
the minus sign (–) produces an inverted
chromatogram.
Autozero on inject Selected by default, this function results in an
autozero each time the detector receives an
inject-start signal via contact closure, Ethernet, or
through the front panel. You can disable this
parameter by pressing any numerical key.
Table 3–1: Detector functions (continued)
Function Description