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Opto-Technology
can decrease the response time to po-
tential quality issues from days to hours.
This depends on the use of autonomous
water monitors—ones that need to be
compact and cost effective—that con-
tinuously test water quality at multiple
locations along the network.
Typical causes of changes in water
quality include natural events, such as
flooding, accidental discharge or spills,
or other sources of contamination. UV
photometry provides quantitative analysis of the organic content in water. By
using continuous spectroscopic measurements instead of intermittent chem-
ical testing with grab samples, end users gather process information, detect
issues in water quality, and make the
necessary process changes in real time.
Traditionally, these water-quality
measurements have used xenon flash
lamps as the light source for spectrosco-
py. Xenon flash lamps provide a broad
spectrum of wavelengths and often re-
quire an expensive photodiode array
for detection. These lamps also require
an expensive power supply to maintain lamp performance. Although these
high-quality instruments offer precise,
accurate measurements of multiple pa-
rameters of water quality, they are often
more than what a typical water facility
requires. The associated costs are also
restrictive to small water utilities, and
unreasonable for developing regions.
Engineers can achieve the same benefits of xenon flash lamps for a subset of
parameters by using UVC LEDs, along
with a less costly detector and power supply. Newly available high-performance
UVC LEDs offer linearity of measurement that matches the performance of ex-
pensive xenon flash lamps. This param-
eter refers to the correlation between the
optical method of water-quality measurement with a reference method (
typically a chemical measurement in the lab). A
more compact, less costly instrument can
thus become accessible to a wider cross-section of the market. Additionally, the
reduced size and low power consump-
tion of these instruments open possibilities for remote monitoring.
Cost analysis of a typical
water-quality monitor
Table 3 provides figures for the typical
cost of a broad-spectrum xenon flash-
lamp-based monitor versus a wave-
length-specific LED version. The UVC
LED instrument assumes fixed wavelength detection at two wavelengths:
255 nm for the standard UV254 measurement and a second UV wavelength
depending on the water-quality parameter of interest. Operating costs are estimated based on a typical water-qual-
ity measurement where the light source
would be used for continuous measurement at a duty cycle of 1% ( 1 ms on,
100 ms off).
Cost-effective, compact
instruments for the future
Traditionally, instrument designs that
used UV lamps could take advantage of
the benefits of the lamp, but unavoidably
had to make concessions in instrument
design due to limitations of the light
source. High-performance UVC LEDs
now enable design engineers to address
market pressure for lower-cost prod-
ucts with instruments tailored for ap-
plications in life sciences and environ-
mental monitoring.
By transitioning to UVC LEDs, in-
strument manufacturers can reduce instrument costs by 40% to 80%. These
cost savings continue at the customer
site due to a large reduction in operating and lamp-replacement costs over a
five-year period. In addition, these “lite”
instrument versions can capitalize on the
instant on/off, low power consumption,
and high-sensitivity features of UVC
LEDs for better performance.
Hari Venugopalan is director of global product management at Crystal IS, Green Island,
NY; email: venugopalan@cisuvc.com; http://
www.cisuvc.com/.