Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Reexamination Certificate
2000-07-27
2002-10-01
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
C250S373000, C422S024000, C385S012000
Reexamination Certificate
active
06459087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a sensor device for intensity measurement of the electromagnetic energy from a lamp device comprising at least one UV lamp preferably of the type arranged in a container in connection with disinfection or photochemical treatment of flowing water, wherein the light intensity is measured using light guide means and sensor means. The invention moreover relates to a UV treatment system, preferably a UV disinfection system or photochemical reaction system, comprising a lamp device with evenly arranged UV lamps and a device for intensity measurement.
2. Description of the Prior Art
U.S. Pat. No. 4 201 916 teaches a sensor device for intensity measurement and a reaction container adapted for disinfection or photochemical treatment of flowing water, wherein the light intensity is measured using light guide means and sensor means, and where the ultraviolet light from the UV lamps in a UV treatment container is measured in a tube opening in the container wall adjacent one of the UV lamps in the container. The position of this tube opening and thereby the measuring point relative to the lamps are selected such that, based on the light radiation characteristic of the UV lamps, the measurement may be expected to be as representative as possible. Most UV lamp manufacturers state a non-uniform light distribution relative to the length of the lamp, particularly in case of low-pressure lamps of U-shape or low-pressure lamps of lengths above 1 meter. Measurement of one UV lamp by a single point measurement of the intensity of UV light, the UV lamp device being presumed to obey a uniform light distribution characteristic, provides only an approximately correct measurement.
EP-A-0 531 159 describes a light detector in which a fluorescent fiber is used for the detection of light of low intensity. The fibers are secured to a panel, which serves as a concentrator or a light collector.
U.S. Pat. No. 4,103,167 discloses a method employing a large number of photodiodes. This method calls for complicated measures without offering the prospect of measuring the real intensity.
In cylindrical containers with more than one UV lamp, e.g. for disinfection of water or other forms of liquids, it is impossible to measure the real energy per volume, and how much UV energy is present at the weakest points in the system by means of only a single point light sensor mounted on the cylindrical container wall.
To be certain that the system carries out a complete disinfection of the water flowing through it, a minimum illumination of the water must be ensured. It has been found in this connection that bacteria, if any, in the water are inactivated by an illumination of at least 5.4 mJ/cm UV energy at a wavelength &lgr;=253.7 nm.
However, it is a problem if there are areas in the container that are not sufficiently illuminated because of one or more defective or malfunctioning UV lamps. To guarantee a minimum of UV illumination of the entire container, the container is illuminated with an UV illumination that is somewhat above the minimum value, which represents an excess of energy consumption and an additional cost burden on the operation of such systems. The high load of the individual UV lamps moreover has the effect that the service life of the lamps is shortened, which in turn adds to the maintenance costs.
The problems outlined above are even more pronounced in ducts or channel systems where the UV lamps—typically mounted in cartridges—are positioned vertically in the channel or in its longitudinal direction. The channels have a rectangular cross-section, and the water flow in them is horizontal in the longitudinal direction of the channels.
UV irradiation of a sensor, that serves to convert the radiation into an electrical signal, may be a problem in case the sensor comprises an ordinary photodiode, which is thereby exposed to a high UV light energy. Even silicon monocrystal, generally considered as the most resistant to UV light among photodiodes, very quickly develops dark spots due to burning by the relatively short waves. When dark spots occur on the crystal, the measurement is wrong, as the calibration of the current signal relative to the UV light energy no longer holds. The error may be corrected by recalibrating the UV sensor. However, after some time, the measurements loses reliability to such extent, that even frequent recalibration of the UV intensity sensor can no longer remedy the problem, and the sensor will have to be replaced.
It is an object of the invention to provide a device for measuring the intensity of the electromagnetic energy from a lamp device having one or more UV lamps in a reaction system, which provides a more accurate and reliable intensity measurement, and which is more economical in operation and maintenance.
SUMMARY OF THE INVENTION
The invention, in a first aspect, provides a sensor device for intensity measurement of ultraviolet (UV) light inside a container carrying a flow of a liquid, comprising a light guide means and a photodetector means, wherein said light guide means comprises two doped light guides, and two differently doped edge glass filters, each of said edge glass filters enclosing a respective one of said light guides, and wherein said photodetector means comprises a respective photodetector positioned at a first end of each of said light guides.
With a device according to the invention it is possible to measure predefined wavelengths of emitted electromagnetic energy along the entire lamp, whereby the total emitted light intensity from the lamp may be measured. The two doped edge glass filters absorb the UV light below a certain wavelength and thus merely allow light having a greater wavelength than the absorption value of the edge glass to pass. The irradiations with which the two light guides are illuminated, thus exhibit different wavelengths. The intensity of the UV illumination of the two light guides is measured by sensor means, which are arranged at the ends of the light guides.
The light guides in a device according to the invention are doped such that the UV light passing through the edge glasses and into the light guides is converted into radiation at wavelengths that are less harmful to the sensor. This results in a considerably longer service life of the sensor means.
For an accurate measurement to be achieved, it is important that there is no great loss of UV light across the edge glass filter. Experiments with an intensity sensor according to the invention have established, that a passage of UV light of more than 92% can be achieved, which is considerably better compared to that of known UV intensity sensors. In addition, a device according to the invention admits UV light from a wide incidence angle or opening angle.
In a preferred embodiment of a light guide device consisting of two light guides, the total opening angle is thus 320° per light guide. It has been found that the sensitivity to light incident from various directions around one light guide device is:
0 to ±145°≧95% and from 145° to 160°≧80%
A light guide device having two light guides in pairs, i.e. total of four light guides may be adapted for an opening angle per light guide of ±115°. In this case the sensitivity is:
0° to ±105°≧95%, and from ±105° to ±115°≧80%
This is a considerable, extremely satisfactory sensitivity for a light intensity sensor.
In order to further reduce the loss of light in the light guides, reflection means are arranged at the other end of the light guides in a preferred embodiment.
In a preferred embodiment for UV disinfection, the first edge glass filter is doped to a filter wavelength of about 245 nm, and the second edge glass filter is doped to a filter wavelength of about 260 nm. This means that a small bandwidth of between &lgr;=245-260 nm is achieved in connection with the measurement of the UV light. Taking the measured signal from the first light guide and subtracting from it the corresponding signal from t
Hannaher Constantine
Jacobson & Holman PLLC
Moran Timothy
LandOfFree
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