Monitor with in-situ optical probe for continuous concentration measurements

An on-site monitor is disclosed for providing automatic measurements of chemical concentrations in a liquid or gaseous environment. The opto-electronic monitor has an extended probe, which can be inserted into the liquid or to be in contact with the ambiance, comprising a indicator chamber for continuously supplying fresh indicator material, a light source, and a detector. The light source and the detector are either embodied outside of liquid or into the extended plastic probe inside the liquid. A delivery unit, which is activated by a timer, delivers a small amount of indicator material into the liquid or a sampling cavity. The indicator material reacts with the ions in the liquid automatically. The light source has a wavelength which matches with the indicator's absorption wavelength and the detector measures the transmission (or reflection) through the indicator material or solution. The optical signal is converted into an electrical signal, calibrated with a known standard, and then displayed on an LED digital meter. The invention has the advantage of automatically and continuously measuring the chemicals on-site with self-powered, low maintenance, and simple operation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to opto-electronic monitors for monitoring 
the quality of a liquid in a pool, a spa, a fish tank, a water reservoir, 
or a water flow system, and more specifically relates to monitors which 
can automatically measure various concentrations in the liquid and display 
their concentration on a low-maintenance and continuous basis. 
2. Background of the Invention 
In hot summer days, dipping into a swimming pool or a spa is one of the 
greatest enjoyment in life. Swimming is also known as one of the best 
exercises in the U.S., where there is a very large number of private 
swimming pools and spas in American families, schools and public 
facilities. However, what has been grossly overlooked by the millions of 
pool users is that no one seems to be able to obtain an accurate and 
up-to-date reading on the quality and sanitary condition of the water in 
the pool. While supposedly the water is periodically tested by the pool 
crew, the quality can drastically deteriorate in a very short time due to 
contamination. 
The pool industry has not responded to this concern very well. In fact, the 
potential health risk has largely been overlooked and ignored. If 
anything, it would be quite comforting for pool users to know the quality 
of the water just before they dive in all the time. So far, pool users 
have mainly relied on the diligence of the pool crew for their own health 
risk, as they have no other way of ascertaining the quality of the pool. 
Or, the more naive ones have found comfort by relying on the fact that 
there are already people in the pool and they seem to be doing just fine. 
Unbeknownst to the population, a pool may have bacteria and algae if not 
properly and regularly treated with chemicals or additives. Prolonged 
exposure to these harmful elements will adversely affect the eyes, skin, 
hair and eventually the overall well-being of every pool user. To ensure 
the overall well-being of the user population, it would be desirable to 
have an on-site pool water monitoring device for accurately determining 
the concentration of the main contaminants, namely acidity, chlorine, 
alkalinity, calcium, magnesium, iron, and bromide, in the pool water. 
There are generally three types of water monitoring devices in the pool 
industry. One of them is the chemical-based indicators, in either solution 
or dip-strip substrate form, which are widely used by private pool owners 
due to their low cost. However, this type of indicators, which is based on 
visual observation of color comparison using standard solutions, is 
inconvenient and often gives inaccurate results. Most pool owners use this 
type of monitors to check pool water quality once every week. To ensure 
excellent water quality on a constant basis, pool owners or users will 
have to check more frequently or around the clock. 
The second type is a hand-held electrode-based monitor which uses 
un-equilibrium electronic charge transfer or electrochemical potential 
between the pool water and the electrolytic cell through a membrane. 
Again, this type of indicator has proven fundamentally unsuitable for 
continuous on-site measurement. The third type of monitors is an 
optical-based monitor as described in an U.S. Patent issued to Saaski, et. 
al., U.S. Pat. No. 5,039,492. This type of monitors employs an optical 
method based on the resulting color change of an indicator substrate to 
measure the pH and gas concentrations in sampling blood. Although this 
method also is derived from the same general optical principle, it is 
intended for only one time use and not for continuous use in a pool or spa 
environment. 
Therefore, it would be desirable to have an on-site water monitor for 
continuously monitoring the quality of the pool water on a low-cost, 
low-maintenance basis. 
SUMMARY OF THE INVENTION 
One of the objects of the present invention is to provide a monitoring 
device for automatically measuring the pH, chlorine, alkalinity, metals, 
and/or bromide concentrations in aqueous solution. 
It is also an object of the present invention to provide a battery, or 
solar, operated monitoring device which is of a simple, inexpensive 
construction and requires minimal maintenance for on-site monitoring. 
It is yet another object of the present invention to provide an in-situ 
extended optical probe for continuous monitoring, where the probe includes 
a continuous supply of fresh indicator material. 
It is also an object of the present invention to provide an automatic pump 
with a tube extended into the liquid for continuously supplying samples 
into the sample cavity for probing. 
A further object of the present invention is to provide a monitoring device 
which continuously displays the chemical concentration on a permanent 
basis. 
Another object of the present invention is to provide a monitoring device 
which can calculate the amount of treated chemical, or balancing 
particles, required to be added to the pool on a permanent basis. 
The foregoing objects can be accomplished by constructing a monitoring 
device comprising an indicator solution or an indicator patch, a light 
source, a detectors, a power supply, signal processing electronics and 
display electronics. The indicator solution or patch may be set up to 
contain separate indicator solutions or patches which are available for 
separate testing of any predetermined particles in the liquid under test. 
The light source, such as a light emission diode (LED) with a wavelength 
matching the indicator's absorption wavelength and the detector, such as a 
photodiode, can be placed either above and away from the pool water or 
inserted into the pool water. A delivery unit, which is activated and 
controlled by a timer, delivers a small amount of the fresh indicator 
solution or unrolls a fresh indicator patch which is attached onto an 
indicator supply strip into the sampling cavity upon contact. The 
indicator material reacts with the ions in the pool water automatically. 
Upon reaction, the color of indicator solution is read by the light source 
and the optical detector. In the case of indicator patches, the reacted 
patch can be forward rolled to the sensor position and read by the sensor. 
The detector measures the intensity of the transmitted light or the 
reflective light through the indicator patch or testing solution in the 
sampling cavity. The optical signal is converted into an electrical 
signal, calibrated with a known standard, and then digitally displayed on 
an LED panel. Based on the measured concentration and the quantity of the 
pool water, the microprocessor can further calculate the amount of treated 
chemical, or balancing particles, needed to be added into the pool to 
ensure water quality. 
The present invention has the advantage of automatically measuring the 
chemicals on-site with a self-powered, low-maintenance, and simple 
operation. As will be appreciated by those skilled in the art, the benefit 
of the present invention to pool users' overall well-being is potentially 
immense. Further, as it will become apparent to those skilled in the art, 
the teaching of the present invention can be applied to monitoring devices 
for monitoring the quality of a variety of liquid or air samples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows one exemplary embodiment of a monitoring device for monitoring 
the quality of any liquid or water in pools, fish tanks, spas, or water 
flow systems in accordance with the present invention. FIG. 2 illustrates 
the system diagram in accordance with its continuous monitoring principle. 
As can be understood by those skilled in the art, the device is capable of 
continuously supplying fresh indicators, measuring the optical 
characteristics of the indicator after its reaction with the ions in the 
liquid, and displaying the measurement on a digital meter. The light 
source and detector can be implemented either inside the liquid or outside 
the liquid to be tested. 
It should be noted that the present invention is described in terms of 
commonly known components and elements, which are the means generally used 
by those skilled in the art in communicating with each other. Based on the 
disclosure of the present invention, those skilled in the art can readily 
implement the present invention, without undue experimentation, for a 
variety of applications. For example, it should be well understood by 
those skilled in the art that the application of the present invention is 
not limited to monitoring water quality in the pool. In fact, with the 
teaching of the present invention, those skilled in the art can readily 
implement various monitoring devices for various kinds of fluids, liquids 
or even gaseous environment. However, the description of the present 
application for use with the pool water is intended to illustrate the 
present invention without unnecessarily obscuring it. 
As in FIG. 1, the monitoring device may be implemented by using a plastic 
molded display case 10 and a plastic molded probe case 50. The display 
case 10 may be implemented to include all the signal processing 
electronics and digital display elements. The preferably elongated square 
probe case 10 should be long enough to be immersed into the water for 
in-situ monitoring. The probe 10 has an indicator reservoir chamber 70 and 
a sampling cavity 80, which are "sandwiched" between a light source 
chamber 60 and a detector chamber 90. The indicator reservoir chamber 70 
holds a large quantity of an indicator material either in a solution form 
71, in a solid form 81 (FIG. 4) or in a patch form 88 (FIG. 5), as will be 
described in connection with FIGS. 3, 4 and 8, respectively. 
FIG. 3 shows one embodiment of an indicator chamber 70 filled with an 
indicator solution 71. The solution is refillable through a small opening 
72. At the bottom of the chamber 70, a valve mechanism is activated by a 
timer 34 (FIG. 1) to deliver one or a few drops of the indicator solution 
at a certain set time. For example, the valve mechanism can include a 
small needle 74, an opening 76 and an O-ring seal 78 to prevent leakage of 
the indicator solution to the pool water. The needle 74 is activated by an 
electronic solenoid 75, which is controlled by the timer 34. Whenever the 
valve mechanism opens up, a pre-set amount of the indicator solution 71 is 
delivered into a sampling cavity 80. The drop of indicator reacts with the 
chemicals in the water and shows nearly instantly a color change. Since 
each measurement requires only one drop 79 of the indicator solution, the 
refilling process will not be needed for a long time, which achieves the 
object of a low-maintenance operation. 
FIG. 4 displays another embodiment of the indicator chamber 70 using a 
solid form indicator material. A roll of the indicator supply strip 81 is 
mounted on a rotating dispenser 82, 83, 84, to continuously supply fresh 
indicator material. A large amount of indicator patches 88, impregnated 
with a solid indicator, may be attached onto the indicator supply strip 
81. Because the indicator patch 88 is made of a porous substrate, such as 
membrane, the pool water can easily diffuse into the pores and react with 
indicator material. The strip 81, which may be made of optically clear 
material, transports the indicator patch from the indicator chamber 70 
through an opening 86 into the sampling cavity 80, and then back into the 
indicator chamber 70 for storage. The rotating dispenser 82, 83, 84, which 
may be implemented with electro-mechanical gears, is activated by the 
timer 34 at a certain set time. 
As shown in FIG. 4, the sampling cavity 80, where the indicator reacts with 
the ions in the water, may be located underneath the indicator chamber 70 
and between the light source 62 and the detector 92. The sampling cavity 
80 is exposed to the pool water for such reaction to take place. 
Therefore, the indicator material is automatically exposed to the pool 
water as soon as it is delivered into the sampling cavity 80. 
The sampling cavity 80 can be five-side physically confined by the walls of 
the indicator chamber, light source chamber, and detector chamber, while 
the bottom side of the sampling cavity 80 is open to the pool water. The 
fresh, or unused, indicator, either in solution form 79 or in solid 
substrate form 88, changes color after it reacts with the ions in the pool 
water. The reaction process may take a few seconds for the indicator to 
homogeneously admix with the pool water. Those skilled in the art can 
readily take advantage of a variety of indicators or organic dyes, which 
have been developed in the industry and which are sensitive to the 
concentration of certain chemical ions. 
FIG. 5 is an angled view of the indicator supply strip 81 with an indicator 
patch 88 rolled into the water, or sample cavity, and disposed exactly in 
the optical beam path between the light source 62 and the detector 92. 
When the timer 34 expires at its preset interval, a fresh indicator patch 
88 is rolled into the sampling cavity 80. When the pool of water disperses 
into the patch substrate 88, the indicator material interacts with the 
chemicals in the water. As can be appreciated by those skilled in the art, 
a roll of strip 81 with a large amount of indicator patches can be used 
for many measurements. The indicator strip 81 with indicator patches 88 
can be replaced when all of the substrates are used up. 
FIG. 6 shows a pH-dependent absorption spectra of SNAFL calcine indicator. 
(SNAFL is a trademark of Molecular Probe Inc.) The absorption or 
transmission intensity of the indicator at a selected wavelength is 
directly related to the ion concentration in the water. The indicator 
material can be easily incorporated into the transparent polymeric 
membrane or substrates. DPD, N, N-diethyl-p=phenylenediamine, is a 
USEPA-accepted method for detecting chlorine for water and wastewater. 
Based on the color intensity at red region, the method can accurately 
detect chlorine from 0 to 500 mg/l. As those skilled in the art can 
readily appreciate, there are quite a few indicators available in the 
industry, which are sensitive to the variety of chemicals in the water, or 
liquid under test. 
FIG. 7 shows a light source 62 and a detector 92 in the light source 
chamber 60 and detector chamber 90, respectively. Both are disposed inside 
the elongated probe case as two arms with the sampling cavity 80 
in-between. The light source 62, such as a light emission diode (LED), 
with an optimum wavelength for characterizing the indicator's absorption 
property, can be used. Various wavelength LEDs are also available for 
selection by those skilled in the art in their particular implementation. 
Light passes through a light source window 64, a sampling cavity 80, a 
detector window 94, and a detector 92 to form an optical path. If the 
light source and detector chambers are constructed with transparent 
plastic cases, the two windows 64 and 94 may not be necessary. The 
photodetector 92, such as a photodiode, is sensitive within visible range 
and can be used for optical intensity measurement. Both the LED and 
photodiode are wired to a DC battery power supply. Note that the power 
supply can also be implemented using solar cells so as to eliminate the 
need to replace batteries regularly. 
FIG. 8 displays another embodiment of a roll of an indicator supply strip, 
similar to FIG. 4, but with the light source 62 and detector 92 away from 
the water. The roll of the indicator supply strip 81 is mounted on a 
rotating dispenser 82, 83, 84, to continuously supply fresh indicator 
patch 88 into the pool water. The reacted indicator patch 88 is then 
rotated to a position located between the light source and the detector. 
The light source 62 and the detector 92 can be installed as part of the 
digital display 10 package and measure the color change of the indicator 
patch 88. This configuration can avoid the possible electrical contact 
with water as shown in FIG. 4. 
With respect to FIG. 8, another embodiment can be implemented, where the 
light source 62 and detector 92 are each connected by individual optical 
fibers, which extend into the water. At the other end of the fibers, the 
fibers are positioned such that the light source fiber can pass its light 
through the indicator patch 88 to be sensed by a sensor at the other end 
of the detector fiber. This embodiment has the advantage of using optical 
fibers to help the light source 62 and detector 92 reach further, for 
example, into a deeper pool. Also, if the pool edge is much higher than 
the water level, this embodiment can use its fibers to reach the water 
without having to place the rest of the electronics near the water. 
Further, if the water is level is subject to change, e.g. in a reservoir, 
the extended reach can prevent the main body of the monitoring device from 
being submerged in the water by allowing the device to be placed afar. 
FIG. 9 is another configuration which shows the device with an additional 
pump 96 which can pump the water sample from the pool into the sampling 
cavity 80 which is located outside and away from the water. The pump will 
be activated by the timer 34 and pump water sample into the sampling 
cavity. The water sample reacts with the newly supplied indicator 
materials, either in solution form or in solid substrate form, in the 
sampling cavity. The color of the indicator material will change according 
to the chemical concentration in the water sample. FIG. 9 shows the 
optical measurement mechanism based on the reflective mode, in which the 
light source 62 and detector 92 are located on the same side of the 
sample, and the detector measures the light intensity reflected from the 
sample/indicator. 
Reference is back to FIG. 2, where the basic principle of the operation is 
described. The user pre-sets the time and frequency or time interval for 
chemical testing on a timer 34. The timer initiates the operation by first 
delivering the indicator material into the sampling cavity which is either 
open to the liquid to be monitored, or can access new samples, then 
activating the light source to illuminate the liquid/indicator solution 
(or substrate), and finally measuring the transmissive, or reflective 
intensity with a detector. 
It should be understood by those skilled in the art that the present 
invention can be readily applied to a method and apparatus for monitoring 
the quality of air or gaseous samples. By allowing the testing material to 
be in contact and react with the samples from the environment, a light 
source can be used to obtain the necessary information based on the color 
change of the testing material. For example, the indicator solution can be 
sprayed, using an atomizer, into the sampling cavity for the light to 
detect any color change. As such, the quality of the environment can be 
monitored continuously. 
After the detector detects the transmitted light, the electrical signal is 
sent to the display case 10 for signal integration, amplification, and 
digitization, as can be readily understood and implemented by those 
skilled in the art. The electronic display case 10 may comprise common 
electronic components such as an integrator/amplifier 36, an 
analog-to-digital converter (A/D) 38, a comparator/microprocessor 40, a 
digital display meter 14 and 14A, a timer 34, and a battery-operated power 
supply 32, or solar cells. A series of known values corresponding to the 
known chemical concentrations will be stored in the comparator for 
calibration. Based on the detection value, the microprocessor can 
determine if the end of indicator is reached or the indicator material is 
running out. A red LED can inform the user that fresh indicator material 
is needed in the indicator chamber. Those skilled in the art can further 
design equivalents for the users to input the quantity of the liquid or 
fluid to be monitored in a unit of .times.1000 gallons. This 
microprocessor 40, based on this pre-set quantity and measured pH, or 
bromide values, can calculate the required treated chemicals for the 
liquid. An eight-segment digital red LED may be used to display the 
reading of the measurement. The meters 14 or 14A will update the 
concentration value whenever a new reading has been initiated. The timer 
34 which controls and initiates the device operation can be preset for any 
period of time interval for testing. 
The information thus obtained can also help determine the amount of 
additional chemicals needed to balance the quality of the water, liquid or 
environment. Using pre-set algorithm and calculation routine, the amount 
of balancing particles needed to maintain, say, the pool water quality can 
be displayed for the user. Or, in the case of a monitoring device for the 
air quality in a room, the information can be used to activate air 
freshener agents to balance the air quality automatically. As can be 
appreciated by those skilled in the art, the continuous and 
low-maintenance operation of the present invention can lead to a truly 
"intelligent" monitor for a variety of applications. 
Once the quality of the liquid can be detected, the present invention can 
also be extended to include a wireline or wireless transmitter to transmit 
the detection result to a remote data processing center. This is 
particularly useful in monitoring the quality of liquids or fluids located 
at different physical locations, such as at different points of a river, 
stream or aqueduct. With this methodology, the quality of a river or 
several of them can be monitored by a central location in a low power and 
low maintenance way. 
Although only a few exemplary embodiments of this invention have been 
described in detail above, those skilled in the art will readily 
appreciate that many modifications are possible in the exemplary 
embodiments without materially departing from the novel teachings and 
advantages of this invention. Accordingly, all such modifications are 
intended to be included within the scope of this invention as defined in 
the following claims. In the claims, means-plus-function clauses are 
intended to cover the structures described herein as performing the 
recited function and not only structural equivalents but also equivalent 
structures. Thus although a nail and a screw may not be structural 
equivalents in that a nail employs a cylindrical surface to secure wooden 
parts together, whereas a screw employs a helical surface, in the 
environment of fastening wooden parts, a nail and a screw may be 
equivalent structures.