US 3856470 A
A rotor assembly for an apparatus adapted for monitoring a chemical reaction and identifying the presence of certain substances in each of a multiplicity of discreet samples. The assembly includes a transfer disc for storing individually the various constituents of one or more independent reactions and a cuvette rotor disposed concentrically thereto. The cuvette rotor provides in the path of light to a photoresponsive device a multiplicity of chambers for receipt of the constituents of each reaction. Means are provided in the cuvette rotor to heat the constituents to optimum temperature and to maintain the constituents at that temperature during the reaction time.
Description (OCR text may contain errors)
United States Patent [191 Cullis et a1.
[ Dec. 24, 1974 ROTOR APPARATUS  Assignee: Baxter Laboratories, Inc., Morton Grove, Ill.
22 Filed: Jan. 10,1973
3,727,832 4/1973 Maclin et al 233/11 3,744,974 7/1973 Maddox et a1... 23/259 3,744,975 7/1973 Mailen H 23/259 3,759,666 9/1973 Hill, Jr. 23/259 Primary Examiner-R. E. Serwin Attorney, Agent, or Firm-Samuel B. Smith, Jr.; Richard G. Kinney  ABSTRACT A rotor assembly for an apparatus adapted for monitoring a chemical reaction and identifying the presence of certain substances in each of a multiplicity of discreet samples. The assembly includes a transfer disc for storing individually the various constituents of one or more independent reactions and a cuvette rotor disposed concentrically thereto. The cuvette rotor provides in the path of light to a photoresponsive device a multiplicity of chambers for receipt of the constituents of each reaction. Means are provided in the cuvette rotor to heat the constituents to optimum temperature and to maintain the constituents at that temperature during the reaction time.
3 Claims, 7 Drawing Figures PATENTEU 555241974 SHEET 2 BF 4 PATEHI niczmm.
ROTOR APPARATUS The present invention generally relates to an apparatus capable of sequentially monitoring several chemical reactions. Through monitoring the presence of certain substances in each of a multiplicity of discreet samples may be determined. More particularly, the present invention relates to a rotor assembly of the apparatus. The rotor assembly includes a transfer disc in which constituents are disposed individually, one from the other, and a cuvette rotor for receipt of the constituents in a multiplicity of optical viewing chambers. The cuvette rotor includes means adapted to heat quickly and accurately the reacting constituents within the chamber and thereafter to maintain the reacting constituents at the temperature to which they were heated.
Typical of apparatus of the type contemplated herein is the computer interfaced analyzer developed under the aegis of the National Institute of General Medical Sciences and the United States Atomic Energy Commission. The computer interfaced analyzer has come to be known as the GeMSAEC system. The system is automated to monitor a reaction from time zero to completion. A readout indicative of all or a part of the reaction may be provided.
For further discussion concerning the interfaced electronics package and, for example, a specific discussion of the make-up of certain embodiments of the transfer disc to store separately the reacting materials until mixed upon operation, reference may be had to U.S. Pat. Nos. 3,536,106, 3,547,547, 3,555,284, 3,582,218 and 3,586,484, issuing to Norman G. Anderson and U.S. Pat. No. 3,514,613, issuing to Douglas N. Mashburn, all of which are assigned to the United States Atomic Energy Commission. For the sake of present discussion the transfer disc may provide at least two wells which are radially spaced from the axis of rotation of the disc. Separate constituents are disposed in each well. A passage, also radially spaced from the axis of rotation, communicates the separate constituents to a chamber of a cuvette rotor of the present invention.
The aforementioned GeMSAEC system while constituting a significant forward step in the biochemical and clinical analyses fields suffers from one significant disadvantage. In this connection and as best as can be determined in the prior art as a whole there has been no attempt to provide means in an automated system to heat and to maintain the reactants at a predetermined temperature.
One important application of the apparatus is the performance of chemical analysis, especially of clinically significant blood enzymes. The apparatus monitors optical changes which occur not only upon mixing of serum with a particular reagent but also during the reaction which follows. The optical changes are stoichiometrically related to the quantity or extent of the chemical reaction. Since the degree of completion of all chemical reactions is temperature dependent, the measurement of chemical reaction processes must reflect a consideration of temperature.
More particularly, however, it is important that the reacting constituents be brought quickly to the desired temperature. In this connection the recordation of data must begin when the reactants are at the appropriate temperature. The measurement of blood enzymes is made by determining the rate at which the enzyme reacts, which reaction will commence as soon as the reactants are combined. Generally, the maximum time allowable for temperature adjustment is about 60 seconds. Preferably, however, the reactants should be at the adjusted temperature, which may be within a range of, for example, 0 to about 50C., within about 30 seconds. The adjusted temperature of the reactants and the specific absolute temperature that chemical reactions are conducted is dictated according to international convention for the procedures contemplated. For example, most test procedures for any given chemical analysis contemplate a specific absolute temperature of either 25, 30 or 37C., corrected to 30C. if conducted at a specific absolute temperature of other than 30C.
The present invention provides in apparatus of the foregoing type means for heating reacting constituents. In one important aspect of the present invention the cu vette rotor incorporates a heating component in substantial intimate contact with the surface of each chamber forming a cuvette cell into which the reactants are received.
As will be described in detail hereinafter the cuvette rotor may be formed of material having good thermal conductivity capability thereby to rapidly conduct heat from the heating structure to the liquid reactants in contact with the walls throughout the chamber region. The material, as will also be described, must have other characteristics in order to prevent occurrence of certain analytical problems and/or deleterious effects. Thus, the cuvette rotor should be formed of a material which is inert so as not to affect the reaction of the liquids and the data being recorded. The material must also present a surface to the reactants which will prevent physical bonding thereto of proteinaceous materials expected to be present in samples of blood. In this connection, it is expected that the cuvette rotor will be subject to repeated use.
As a further aspect of the present invention, the heating component within the cuvette rotor is subject to regulation. The heating component provides within critical tolerance accurate heating capability within a range of temperatures as required for any test procedure. In accordance with this aspect of the invention the heating component is continually monitored so as to maintain the temperature of the reactants at the reg ulated level of heat energy.
In a further aspect of the present invention, there is provided means in the cuvette rotor to exhaust the re actants from the chamber after the desired data has been derived. To this end the cuvette rotor provides siphon structure communicating with each chamber. During data retrieval the siphon is inoperable. However the addition of pressure to the chamber causes the re actants to exit the chamber. The exhausted reactants are collected as waste. Additional pressure will likewise be required during the washing of the cuvette chambers after each test and preparatory to a subsequent test.
An additional aspect of the present invention is in the incorporation of means in conjunction with the cuvette rotor to prevent a buildup of a static charge of electricity on the rotating optical surfaces. The buildup of a charge may be prevented by the use of a grounded metal foil gasket in contact with the optical surfaces.
The foregoing description serves to outline in broad terms certain of the more important features of the invention in order for the description in detail which follows to be understood, and in order for the present contribution to the art to be better appreciated. There are, of course, additional features of the present invention that will be particularly described below which also will form the subject of the claims appended hereto. Those skilled in the art to which the present invention pertains will appreciate that the conception upon which this disclosure is based may readily be used as a basis for the design of other structures for carrying out the several purposes of the invention. It is important, therefore, that the claims be regarded as including such equivalent construction as do not depart from the spirit and scope of the invention.
The accompanying drawings, forming a part of the present application, illustrate a preferred embodiment of the present invention. By the drawings FIG. 1 illustrates in elevation and partly in section an apparatus for use in measuring chemical reactions;
FIG. 2 is a bottom plan view of a portion of the rotor of the apparatus of FIG. 1, and particularly the portion of the rotor capable of being heated under controlled conditions;
FIG. 3 is an exploded view of the rotor portion of FIG. 2;
FIG. 4 is a top plan view of the structure of FIG. 2;
FIG. 5 is an enlarged view of the portion of FIG. 4 which is denoted by the circle in phantom;
FIG. 6 is a cross-sectional view as seen along the line 66 in FIG. 5; and
FIG. 7 is a schematic view of the heating and sensing circuit as employed.
The structure as seen in FIG. 1 of the drawings illustrates only a small portion of the overall apparatus which may be used in monitoring, in response to light transmittance criteria, a chemical reaction for determination of the presence of certain substances in a discreet sample. The apparatus is particularly adapted for use in the rapid and accurate evaluation of the presence (or absence) of substances in a patient serum sample identifiable with an abnormal condition. In the embodiment of the invention to be discussed below there is a capability of sequentially identifying and monitoring fourteen chemical reactions. Monitoring is carried out almost simultaneously. These reactions are compared against a known sample which is disposed in one of fifteen cuvette chambers. Any number of cuvette chambers corresponding to the number of groupings of radially spaced wells in the transfer disc may be provided as is practical.
The FIG. 1 structure generally includes a housing having an upper portion 12 providing a chamber 14. The rotor assembly 16 to be described is disposed for movement within the chamber. A lower housing portion 18 serves to enclose a shaft 20 which is received in the upper housing. The shaft at one end is connected to the rotor. Any means known to the art may be employed. The shaft at the other end is coupled by suit able gear means to a drive motor (not shown).
A collar 22 is supported by the housing members. To this end the collar includes a radial flange 24 which is supported by shoulder 26 of the upper housing. A plurality of set screws 28, only one being shown, circumferentially spaced about the flange are employed to mount not only the collar as discussed but also connect the upper and lower housings.
The collar member additionally provides an annular cutout 29 at both the top and bottom. Bearing members 30 secured to the shaft are disposed in each cutout for apparent purposes. Sealing members 32, likewise, are disposed in each cutout. The sealing members are of cylindrical and generally Lshaped form. The base of each member is cemented or otherwise mounted to the collar so that the extended portion extends generally perpendicularly toward and into wiping contact with the shaft 20. The sealing members serve to prevent patient serum or reagent material from passing into the region of the drive motor housing.
The rotor 16 includes a transfer disc 34 and a cuvette rotor 36. As briefly discussed the cuvette rotor includes several chambers. Both the transfer disc and the euvette rotor are supported by a plate 38. The rotor additionally includes a top plate 40. The top plate is of annular construction and includes an annular extending skirt portion 42 for purposes hereinafter discussed. A plurality of mounting screws 44 circumferentially spaced about the rotor periphery connect together certain of the rotor components including the cuvette rotor and the plates to permit rotary movement of the rotor assembly within the upper housing. The transfer disc is supported by the lower plate 38 and is readily removable from within the annulus defined by the cuvette rotor.
As indicated, the apparatus is capable of the rapid and accurate evaluation of reactions in which one of the reactants is blood serum from a patient. The rate of reaction will normally be evaluated over a period from time zero at which time the reactants are first brought together to completion or the end point of the reaction.
To accomplish the purpose of first isolating the reactants and then quickly bringing them together the transfer disc in the upper surface includes a plurality of pairs of radially spaced chambers 50, 52. In the present embodiment there are fifteen pairs of chambers. Typically serum from a patient will be disposed in chamber 52 while reagent will be disposed in chamber 50. Each chamber of each group ofchambers is internally loaded with a finite and precise volume. Loading may be accomplished by any of the known clinical techniques which are commonly employed.
The transfer disc may be constructed of any metal or plastic material which is, among other factors, sturdy in use and not deleteriously affected by patient serum or any one of the various reagents used in testing for glucose, bilirubin, albumin, LDH (lactic dehydrogenase), to name only a few of the well-known and documented test procedures. While many metal or plastic materials have been used successfully. a transfer disc formed of plastic, such as polytetrafluoroethylene polymer, commonly referred to as TEFLON is preferred. TEFLON is a registered trademark of E. I. du Pont de Nemours and Company.
The transfer disc 34 includes a further well 54 constituting a first mixing chamber. Thus, through rotation of the rotor assembly and upon the development of centrifugal forces through rotation the serum and reagent will transfer from their respective wells into the mixing chamber 54. A port 56 in the wall of the transfer disc serves to pass the reagents into an aligned cavity or chamber in the cuvette rotor 36.
A cover assembly (not shown in full detail) is supported by the housing to enclose the area of the wells 50, S2 and 54. The cover assembly includes an inner cover 51 which, however, is shown in the Figure. The inner cover provides generally a flat under surface and a downwardly depending skirt portion to surround the outer upstanding wall of the transfer disc in a loose fit. The remaining components of the cover assembly may be supportingly received on the housing over the inner cover by a hinge structure or equivalent means and may be held in the closed position by a spring loaded latch mechanism. An O-ring is suitably disposed between the cover assembly and the wall at a shoulder in plate 40 to seal the chamber area of the transfer disc from the chamber 14. Thus, the reagents will entirely move through the port 56.
The cuvette rotor 36 will be discussed in greater detail below. For the present discussion, however, suffice it to say that the reagents are held captive and mixed in the cuvette chambers once having entered the same during rotation of the rotor and the developed centrifugal forces. Viewing windows 58 are positioned both above and below the cuvette chambers. The viewing windows may be of any optical material capable with out significant absoprtion of passing light both to the reagent sample within the cuvette chambers and thereafter passing the light not absorbed by the reagent to a photosensitive means. The viewing windows may be plexiglass, pyrex glass or quartz, for example. The viewing windows in the preferred embodiment are formed of quartz. One reason is that quartz windows will permit ultraviolet measurement. Both viewing windows are annular in outline.
The overall apparatus functions to compare the analog response to the amount of light transmittance from one of several cuvette chambers with the criteria from the reference cuvette chamber. However, the readout preferably is in digital form. Therefore, the output of a photoresponsive means, such as a photomultiplier 60, which is proportional to the value of light transmittance of the reagent within the cuvette chamber, is converted into a digital output reading and compared in a computer with the digital output reading indicative of a sample.
As illustrated in FIG. 1 light from a source (not shown) is reflected by mirror 62 toward the photomultiplier tube. The photomultiplier tube is supported within a housing 64. The housing except for the light slot 66 is completely enclosed to prevent stray light from impinging on the photoresponsive tube. As appar ent, the lower housing and the rotor plates each provide a path for light along the path (illustrated by arrow 68) from the mirror 62 to and through the housing slot 66. Each plate preferably provides a plurality of apertures disposed in alignment with each of the several cuvette chambers.
The apparatus may be utilized in the conduct of any one or more of the many known tests performed on patient serum. Generally, the individual test results will require utilization of light at different frequencies. To this end the housing may accommodate a filter of the chosen frequency. It is also contemplated that a monochromated light may be used. A plate 72 including a central aperture is supported by the housing and in turn supports the filter. Typically, provision will be made for replacement of one filter for another, as required by the particular test.
The cover (not shown) may be apertured within a central region. A seal and bearing structure may be disposed in the aperture. The structure may be positioned in abutting relation to the end of shaft 20 to provide a bearing surface for shaft rotation. The seal functions to permit communication both of air under pressure and wash solution from an external source to an upper hollow portion of the shaft. The hollowed portion of the shaft includes a multiplicity of spaced radial holes, one of which is preferably directed toward each cuvette chamber. During the period when the reaction is monitored air may be drawn through the seal and shaft into the cuvette chamber by a vacuum created along the path of siphon from the cuvette chamber. The air aids in the complete mixing of serum sample and reagent.
Generally, the information received by the computer is stored according to its program. Thereafter, consis tent with the computer program a digital readout is provided. When the data retrieval phase of the operation has been completed each cuvette chamber is pressurized by air pressure from the external source causing a siphoning of liquids from the cuvette chambers. The liquids, referring to FIG. 1 are siphoned into the chamber 14 and through housing opening to a waste collection point. The cuvette chambers are thereafter washed, rinsed, centrifuged and blown clear in like manner to condition the rotor assembly for a subsequent test procedure. It is to be noted that a siphoning action will commence only with the application of air under pressure greater than the centrifugal forces acting on the liquids in the cuvette chamber during rotation. The skirt 42 serves substantially to prevent an aerosol from the liquids being siphoned being formed within the chamber. Such an aerosol may pass to the inner confines of the chamber or merely collect as a contaminant within the chamber.
The cuvette rotor 36 may be seen to best advantage in FIGS. 2 and 4 of the drawings. The rotor is in the form of an annulus having a plurality of indentations defining individual chambers 102 which are equidistantly spaced one from the other. In the preferred embodiment there are fifteen chambers. each disposed radially of the wells 50, 52 and 54 in the transfer disc 34.
The cuvette rotor is formed of a material which may be cast, milled or otherwise shaped to the configuration as shown in the Figures. Either plastic materials or metal may be utilized. Choice of material is dependent upon certain factors. To this end, the material must at least be of high thermal conductivity to display good heat transfer capability, it must also be inert so as not to react with those liquids which will contact its surfaces during operation, it preferably should display low surface energy characteristics, it should be subject to machining thereby to provide an extremely smooth surface to prevent adherence of chemical matter in any irregularity, and it must be easily and completely clean able. The cuvette rotor is preferably formed of either an aluminum or brass substrate and thereafter coated with a thin film, i.e., about 0.005 inch in thickness. The film includes an application of electrodeless nickel and an outer layer of gold electroplated thereon.
[t is contemplated, also, that various plastics may be used in substitution for the nickel and gold layer. These plastics include TEFLON, polymers of trifluorochloroethylene (KEL-F) and vinylidene fluoride resins (KYNAR). KEL-F and KYNAR are registered trademarks of M. W. Kellogg Company and Pennsalt Chemicals Corporation, respectively. These materials display low surface energy characteristics, are capable of undergoing machining or polishing to a smooth surface and may be deposited on the aluminum or brass substrate in a thickness on the order of 0.005 inch. The
thickness of the plastic is such that the characteristic of heat transfer from the substrate to the liquids in the cuvette chamber is not significantly diminished. The plastics are also inert to the liquids in the cuvette chambers such to display immunity to protein adhesion on the walls of the chambers.
The heater structure is disposed within the substrate. More particularly, the substrate is cut out within the lower surface and the area bounded by the circular line 104 and the line 106 to a depth of approximately 0.0070 inch. The area of the cutout and consequently the area of the heater is significant with respect to the total surface area of the substrate. By this relationship, a high ratio of heater area to surface area is provided. The heater structure is in the form of a printed circuit. A layer of insulation, such as a glass-filled TEFLON (KAPTON), a tradename of The Connecticut Hard Rubber Company or an equivalent insulation material, such as fiberglass cloth with a nitrile rubber filler and binder, may be both disposed on the outer side of the heater. The insulated printer heater circuit is bonded to the substrate by any one of the many adhesive materials. The entire heating package may be on the order of 0.008 inch in thickness.
A connector 108 is supported within the substrate for electrical connection of the resistance heater to a source of power. A temperature sensing element which may be a thermistor 110 is supported within the substrate. A connector 112 supports the thermistor within an aperture in the substrate. The thermistor extends toward a single one of the many chambers 102. The thermistor preferably is disposed relatively closely to both the wall of the chamber and the resistance heater so that the sensor probe will rapidly detect a low temperature condition of the chamber liquids to cause automatic increase in heater output. The sensor, likewise, will rapidly react to high temperature in the chamber liquids to automatically control or stop heater output. Preferably the sensor will be disposed approximately 0.125 inch from both the resistance heater and the wall of the chambers 102.
A siphon 114 is formed within the upper surface communicating the outer periphery of the annulus with each of the several chambers 102 throughout a general S-shaped path. The depth of the path will be about 0.040 i 0.002 inch. As heretofore discussed, the centrifugal force exerted on the reactants within the chambers 102 because of rotation of the rotor is not sufficient to cause the reactants to exit the chamber by way of the siphon. As also discussed, air under pressure from an external source is introduced to the several chambers for the purpose of first evacuating the chamber of reacting liquids and thereafter of wash solutions introduced thereto. The rear wall of the chambers are inclined at 116 (see FIG. 4) to aid in movement of the liquids toward the entrance to the respective siphon.
Referring again to FIG. 4 it will be noted that the surface of the annulus within the space generally between the consecutive chambers is cutout at locations 118 and 120. The relief throughout the upper surface will be approximately 0.025 inch. The relieved area throughout the upper surface serves to reduce the overall weight of the cuvette rotor annulus.
FIG. 3 illustrates the several component parts defining the rotor 16. [n this connection the Figure illustrates the transfer disc 34 and cuvette rotor 36 in surrounding relation. A gasket member 130 is supported on opposed sides of the cuvette rotor. One gasket provides a support surface for the upper annular optical piece 58 and together with the piece serves to provide an upper seal for each chamber 102. The gasket may be bonded to the optical piece by any means, such as a room temperature vulcanizing medium of nitrile or silicone rubber. The second gasket serves a like function when disposed between the lower surface and the lower optical piece and likewise may be bonded to the optical piece. The relieved surface area together with the wall adjacent the path of the siphon provides a ridge upon which the gasket is disposed. The ridge enhances the seal obtained between the substrate and the upper optical piece.
Each gasket 130 is configured to provide a constant radial perimeter and an inner contour which duplicates the outline of the wall bounding each chamber and between chambers. The diameter of the gasket will be equal to the outer diameter of the annular optical pieces. The diameter is slightly in excess of the diameter of the outside wall of the relieved area 118.
A second pair of gaskets 132, both of annular form and having an outer diameter equal to the outer diameter of the gaskets 130 are disposed on the other sides of the optical pieces 58. Each gasket includes a plurality of apertures which are equidistantly spaced to permit the passage of light along the path 68. The inner diameter of gaskets 132 will be generally equal to the inner diameter of both the optical pieces 58 and the cuvette rotor 36. Both the gaskets 130 and 132 may be formed of any one of neoprene, Buna-N or silicone rubber. As heretofore stated, the total cycle of the apparatus requires a washing and cleaning stage as well as a stage during which liquids within the cuvette chamber are expelled. These operations utilize air pressure thereby to pressurize each chamber. The force exerts special stress on the liquid sealing areas, for example, the seal between the cuvette rotor and the optical window. Thus, the seal must be liquid and air tight to at least a value of 25 pounds per square inch. The material of the seal is also resistant to cold flow and any deformation as a result of constant temperature recycling. They are also resistant to chemical interaction with blood components.
An annular foil element 136 duplicating the shape of gasket 132 is disposed between the gasket and the upper optical piece. The foil may be formed of gold or aluminum and serves the function of dissipating any build-up of a static electrical charge on the optical member. The charge may develop and accumulate on the upper optical surface because of friction associated with the rotating parts. No static electrical charge will build on the lower optical surface because of the continual liquid contact therewith. The foil through any particular means (not shown) is grounded thereby bleeding the electrical potential substantially to prevent the adherence of airborne particles on the optical surface at the cuvette chamber.
The structure as discussed above is sandwiched together and secured between the lower rotor plate 38 and the upper annular plate 40. To this end the cuvette rotor includes a plurality of holes 140 through which the mounting screws 44 are received.
A typical circuit may be seen in FIG. 7. The circuit provides in series through connectors 108 and 112 connection of the resistance heater 122 and the thermistor 110. Electro-mechanical slip ring structure (not shown) may be utilized to couple the series components to electrical power.
In operation, precise volumes of patient serum and reagent are dispensed or otherwise disposed in the wells 50 and 52 prior to the commencement of any program of operation. An additional reagent may be dispensed or disposed in the well 54, if desired. Upon commencement of rotation of the rotor, which may attain a speed of up to 3,000 rpm, the serum and reagent(s) are rapidly propelled generally outwardly toward the well 54 and port 56 undergoing some mixing prior to entering the cuvette chamber which with the optical members form an optical cell. Since mixing of liquids has commenced and thereafter continues in the optical cell it is imperative that the liquids be quickly brought to the optimum temperature. This has been discussed. The apparatus may operate in accordance with a fast rate over approximately 96 seconds during which absorbance readings are printed and displayed every 3 seconds or in accordance with a slow rate over approximately 8 minutes during which absorbance readings are printed and displayed every 15 seconds. Light from a source is reflected along the axis of the optical cell toward the photoresponsive device. The optical members are approximately mm in thickness and are of a material which will pass substantially all source light to the optical cell and that light passing through optical cell to the photoresponsive device. Thus, the amount of absorbance or transmittance will be determined by the liquid in the optical cell. After the reaction is complete the liquids are expelled from the optical cells by the introduction of air pressure. A washing and cleaning cycle may be employed preparatory to a subsequent test. For this purpose both wash solution and thereafter air under pressure is introduced to the chamber of the transfer disc to clean the same through rotation, expell the liquids and dry the chamber walls.
Having described the invention, I claim:
I. In a photometric solution analyzer comprising a power-driven rotor assembly which defines a multiplicity of sample analysis chambers for accepting liquid samples to be analyzed, said rotor assembly having transparent walls adjacent said sample analysis chambers for permitting the passage of light therethrough and a multiplicity of chambers adapted to retain liquid samples and reactants when said rotor assembly is at rest, and to release said liquid samples and reactants to said sample analysis chambers when said rotor is rotated; and stationary photometric means for detecting changes in the analysis chambers by passing a beam of light through the transparent walls of said rotor assembly, the improvement comprising:
electric powered temperature adjusting means mounted on, and rotatable with, saidphotometric assembly;
electric output producing temperature sensing means mounted on, and rotatable with, said photometric rotor assembly; and
means coupled to said temperature adjusting means and said temperature sensing means for controlling the temperature adjusting means to precisely maintain the temperature of said photometric rotor as sembly at a selected value.
2. The invention of claim 1 wherein:
said temperature adjusting means is a resistance electrical heater, said rotor assembly is, in large part, formed of a heat-conductive material, and said electrical heater is disposed in a flat layer adjacent to the said rotor assembly.
3. The invention of claim 2 wherein:
said temperature sensing means is a thermistor and is mounted away from said flat temperature adjusting means, in proximity to a wall of an optical cell of the rotor apparatus, and within the conductive material of the rotor assembly.