Claims
- 1. Apparatus for optical analysis of a sample comprising a body having receptacle means for receiving a sample vial, illumination means for illuminating said sample vial through a base of said vial, and detector means for detecting light which has passed through said sample vial, wherein said receptacle means comprises holder means for engaging said base of said vial and integrator means spaced from said holder for surrounding the upper part of said vial and integrating light emerging from said vial.
- 2. Apparatus according to claim 1 wherein said illumination means comprises a source of light and a mirror for directing said light toward said holder.
- 3. Apparatus according to claim 1 wherein a body of said vial is cylindrical, and said mirror directs light in the direction of a longitudinal axis of said body.
- 4. Apparatus according to claim 3 wherein said source of light comprises a first source of light of a first wavelength and a second source of light of a second wavelength, wherein light of said first wavelength provides a reference illumination.
- 5. Apparatus according to claim 4 further comprising means for determining the difference between the logarithms of the signals from said detector for each of said wavelengths.
- 6. Apparatus according to claim 1 wherein said body has a recess and said receptacle means further comprises a door for covering said recess and means for pivotally attaching said door to said body, wherein said holder is attached to said door.
- 7. Apparatus according to claim 6 wherein said means for pivotally attaching said door to said body is at one end of said door.
- 8. Apparatus for optical analysis of a sample comprising a body having receptacle means for receiving a sample vial, illumination means for illuminating said sample vial through a base of said vial, and detector means for detecting light which has passed through said sample vial, wherein said receptacle means comprises holder means for engaging said base of said vial and integrator means spaced from said holder for integrating light emerging from said vial and further comprising analog to digital converter means for supplying a digital processor with digital signals derived from said detector, means for changing the sensitivity of the measurement comprising means for supplying a reference voltage to said analog to digital converter means, and means for adjusting said reference voltage.
- 9. Apparatus according to claim 8 wherein said means for supplying a reference voltage comprises a variable output regulator.
CROSS REFERENCE TO COPENDING APPLICATION
This is a continuation of my U.S. Application 412,453 entitled "Portable Colorimetric, Instrument" which was filed on Sept. 26, 1989.
This invention relates to the art of analytical instruments. In particular, the invention is a portable instrument capable of performing accurate spectrophotometric measurements in the field.
It is known to measure the concentration of a substance by addition of a reagent which reacts with the substance to produce a colored compound, the optical density of which is a function of the concentration of the substance.
The use of a narrow ampoule for receiving a sample for colorimetric measurements is also know and is described in U.S. Pat. No. 3,634,038.
Spectrometric measurements are generally made with a technique which provides a reference signal. The use of light having two wavelengths wherein one of the wavelengths serves as a reference is shown, for example, in U.S. Pat. Nos. 3,887,281 (Kurita) and 4,297,579 (Spaeth). These references teach comparison of the reference and sample signals by electronically producing the difference of the logarithms of the signals.
In accordance with the invention, a portable instrument is provided which is capable of accurate colorimetric field measurements of substances such as dissolved oxygen. The instrument includes a body which has a receptacle for an elongate cylindrical vial which is self-filling. In the preferred embodiment, a door is pivotally attached to the body and has a holder for receiving the vial. When the door is opened, preferably by pivoting it 45.degree. with respect to the body, the vial may be inserted into the holder. When the door is closed, the vial is automatically placed in the proper position in the receptacle.
The body encloses an optical system for illumination of the vial. The optical system comprises two sources of light, a first of the sources producing light which is absorbed by the sample and the second of the sources producing light which is absorbed only to a small degree by the sample. The light from the first source is the measuring beam while the light from the second source is a reference beam. These beams are produced by alternatingly powered light emitting diodes (LED).
When the vial is in the receptacle, it is aligned with an optical path of an illuminating beam produced by the first and second sources of light. Preferably, the optical path is aligned with the longitudinal axis of the vial so that the path length of the beam in the sample is as long as possible. In a preferred embodiment, the light path within the fluid sample is about 70mm. The light enters through the base of the vial and exits from the top of the vial. A light integrator surrounds the top of the vial and directs the emerging light to a diffuser and a detector. The integrator preferably comprises two semi-cylindrical parts. One of the parts is in the body of the instrument, and the other is in the door so that the two match to form a complete cylinder when the door is closed.
The signals from the light detector are directed to an amplifier and to a microprocessor which determines the difference between the logarithms of the two signals along with other signal processing which will be described in more detail below.
An object of this invention is to provide a highly accurate portable instrument capable of field measurements.
Another object of this invention is to provide a portable instrument into which a self filling vial may easily be inserted for performing colorimetric measurements in the field.
US Referenced Citations (25)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| WO8200361 |
Feb 1982 |
WOX |
Non-Patent Literature Citations (1)
| Entry |
| "Double-Beam Densitometer and Comparator", by Carpenter et al. Analytical Chemistry, vol. 25, No. 10, Oct. 1953, pp. 1473-1477. |
Continuations (1)
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Number |
Date |
Country |
| Parent |
412453 |
Sep 1989 |
|
Patent Grant
5013155
