Teledyne 6650 - Fluorescence Probe - Oil in Water analysis system - Manual (Page 12)

Definition of Terms Model 6650
4 Teledyne Analytical Instruments
Definition of Terms
2.1 Excitation Filter
The excitation filter is used to select the range of wavelengths, the
pass band, used to cause or excite the molecular fluorescence.
Wavelengths not in the pass band are rejected and ideally never reach
the sample. Removal of wavelengths outside the pass band minimizes
the possibly of false fluorescence readings due to detection of light from
the lamp which mimics the fluorescence signal.
2.2 Emission Filter
The emission filter is used to select the range of wavelengths, the
pass band, to be passed to the measure detector. Wavelengths not in the
pass band are rejected and ideally never reach the sample. It is critical
that the excitation wavelengths never reach the detector, since it will
respond to excitation light. Excitation light impinging the measure
detector results in increased residual background levels, which reduces
the dynamic range, the signal-to-noise ratio and the signal-to-blank ratio.
2.3 Measure Detector
The light detector is most often a photomultiplier tube, though
photodiodes are increasingly being used. The light passing through the
emission filter is detected by the photomultiplier or photodiode. The
light intensity, which is proportional to the analyte concentration, is
registered as a digital readout.
2.4 Span Filter
The span filter is used to check instrument operation. When a
fluorescence filter is employed the span filter fluorescence value is
dependent on the initialization method utilized and the standards used
during calibration. The span filter is used to verify instrument operation
and should not be used to calibrate the instrument.