APPENDIX I: THEORY
TD1000C™Oil in Water Monitor
46
TD-1000C Oil In Water Monitor
Operation Manual
PN 101687
REV G
APPENDIX I: THEORY
The TD1000C™ measures the sample hydrocarbon level by means of fluorescence. Fluorescence
occurs when a molecule—in this case a hydrocarbon molecule—relaxes to its ground state after being
electronically excited. Fluorescent hydrocarbons absorb light—excite—at one wavelength and emit
light—relax— at a longer (less energetic) wavelength. The emitted light is filtered and translated to a
voltage response which corresponds to the concentration of fluorescent hydrocarbons in the sample.
When compared with other hydrocarbon in water detection and concentration measurement methods
such as ultraviolet or infrared spectrophotometry (absorption), the TD1000C™ offers:
1. Higher intrinsic sensitivity, from 100 to 1000 times greater than pure absorption detection
methods;
2. High selectivity, by “targeted hydrocarbon” optical tuning, minimizing chemical interferences
and sample turbidity false alarms; and
3.
Low maintenance due to the flow cell and solid state electronic design.
The TD1000C™ contains five important components that it uses to make the fluorescence
measurement:
1. Light Source
2. Excitation Filter
3. Sample Cell
4. Emission Filter
5. Light Detector
The TD1000C™ electronics and a highly sensitive light detector allow oil to be detected from the parts-
per-million (ppm) to parts-per-billion (ppb) range.
Light Source
The TD1000C™ utilizes a LED light source to emit photons over a wavelength range tailored to the
application.
Excitation Filter
The excitation filter narrows the range of wavelengths that reach the sample.
Sample Cell
The sample cell is the portion of the sample block where the water sample is exposed to the light
transmitted by the excitation filter.
Emission Filter
The light emitted by the sample passes through an emission filter, which narrows the range of
wavelengths once again. This ensures only the desired wavelengths—those emitted by the targeted
oil— are transmitted to the light detector.
Light Detector
The light detector produces a pulse of electricity when it detects a photon that has passed through the
emission filter. The TD1000C™ counts these pulses and relates that value to the stored calibration
value to determine the oil content of the water passing through the sample cell.
Summary of Contents for TD1000C
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