Waters 2489, Руководство оператора

Страница: 28 / 234

1-12 Theory and Principles of Operation
• Filter time constant – Programs a filter time in seconds. Options are
Fast, Slow, Normal, or Other. If you select Fast, Slow, or Normal, you do
not need to enter a value. The filter constant is determined by the data
rate. If you select Other, you can enter a value, but the value you enter
will be rounded up or down to a value based on the data rate. Selecting
Other and entering a value of 0.0 disables all filtering.
• Analog rate – Specifies a value up to 80 Hz.
Secondary parameters
When on the absorbance (or HOME) screen in single wavelength mode,
pressing Next brings you to several pages of these secondary, or less
frequently specified, parameters:
• Absorbance offset (in mV)
• Auto zero on inject
• Auto zero on
λ
changes
“Primary and secondary functions” on page 3-14 and the Table titled
“Absorbance and message screen icons” on page 3-4 explain the functions,
ranges, and defaults of these parameters.
Dual wavelength mode
In dual wavelength mode, the detector can monitor two wavelengths, one on
channel A and one on channel B. The sampling frequency is reduced to 1 or
2 Hz, limiting use of this mode to more standard chromatography where peaks
span at least 20 seconds to enable full characterization of a peak. You can use
dual wavelength mode to obtain additional information about an analyte by
running a RatioPlot or a MaxPlot.
The detector allows you to select any two wavelengths from 190 to 700 nm.
In dual wavelength mode, the following conditions apply:
• If both selected wavelengths are greater than 370 nm, the detector
applies the second order filter to block unwanted UV light.
• If both selected wavelengths are less than or equal to 370 nm, the
detector removes the second order filter.
• If the selected wavelengths bracket the 370 nm threshold, the detector
does not apply the second order filter and issues a warning message that
any data collected for the wavelength above 370 nm may contain