FLOW-THROUGH MEASURING CELL

Abstract

A flow-through measuring cell having one inlet opening for entry of the fluid, and one outlet opening for exit of the fluid. A single measurement space is located between the inlet opening and outlet opening. A radiation measurement region is provided for measuring the interaction of the fluid in the measuring cell with electromagnetic radiation from outside the measuring cell. The radiation measurement region is bordered by two opposite windows of which one is intended for inlet and the other for exit of the electromagnetic radiation. The measuring cell has a positioning range with several operating positions with a different distance A, A between the windows into which the measuring cell can be set without rotation.

Claims

1. A flow-through measuring cell comprising: an inlet opening for entry of a fluid; an outlet opening for exit of the fluid; a measurement space located between the inlet opening and the outlet opening; a radiation measurement region for measuring the interaction of the fluid in the measuring cell with electromagnetic radiation from outside the measuring cell, the radiation measurement region bordered by two opposite windows, a first of said windows for inlet of the electromagnetic radiation and a second of said windows for exit of the electromagnetic radiation, the measuring cell having a positioning range with a plurality of operating positions, each of said operating positions defining a different distance A, A between the windows into which the measuring cell can be set without rotation.

2. The measuring cell as claimed in claim 1, wherein the measuring cell, after setting of a first operating position, is adjustable within the positioning range.

3. The measuring cell as claimed in claim 1, wherein the measuring cell is formed at least in part from plastic and/or rubber.

4. The measuring cell as claimed in claim 1, wherein the operating position can be set or adjusted along a fit of the window or a window receiver which accommodates the window in the measuring cell.

5. The measuring cell as claimed in claim 1, wherein at least one of the windows can be adjusted or set to one another along their alignment along a guide channel corresponding to an outside contour of the window.

6. The measuring cell as claimed in claim 1, wherein the positioning range extends from the smallest settable distance A, A at least by a factor of 1.5 of the smallest settable distance A, A.

7. The measuring cell as claimed in claim 1, wherein there is direct fitting of the windows relative to the respective guide channel of the measuring cell or of measuring cell body, said channel made as shaping of the measuring cell body.

8. The measuring cell as claimed in claim 2, wherein the measuring cell is adjustable within the positioning range exclusively in the direction of the opposite window.

9. The measuring cell as claimed in claim 5, wherein at least one of the windows is adjustable by frictional engagement in the guide channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a cross sectional view of a first embodiment of a measuring cell as claimed in the invention,

[0027] FIG. 2 shows a cross sectional view of a second embodiment of a measuring cell as claimed in the invention,

[0028] FIG. 3a shows a perspective view of a third embodiment of a measuring cell as claimed in the invention,

[0029] FIG. 3b shows a cross sectional view of the embodiment according to FIG. 3a along one sectional plane As and

[0030] FIG. 3c shows a cross sectional view of the third embodiment along one sectional plane Bs from FIG. 3a.

DETAILED DESCRIPTION OF THE INVENTION

[0031] In the figures the same elements and elements with the same functions are identified with the same reference numbers.

[0032] FIG. 1 shows a measuring cell 1 through which a fluid can flow and which has the measurement space 4 which is bordered by a measuring cell body 5. A fluid flows through the measurement space 4; the interaction of the fluid with electromagnetic radiation, especially light from a light source, is to be measured.

[0033] For this purpose there is a radiation measurement region 6 on which electromagnetic radiation is routed through the fluid transversely to the flow direction of the fluid from a radiation source which is not shown, especially a light source. The electromagnetic radiation is measured on the opposite side.

[0034] In the beam path (beam direction transversely to the flow direction) there are windows 7, 8 in order to allow the passage of the electromagnetic radiation through the measurement space 4 into the fluid. The windows 7, 8 are each routed in the guide channels 11, 12 whose inside contour corresponds to the outside contour of the windows 7, 8 so that there is a fit between the windows 7, 8 and the respective guide channel 11, 12. This enables an adjustment of the windows 7, 8 along the inside contour of the guide channels 11, 12 so that a distance A between the windows 7, 8 can be set or adjusted. This distance A corresponds especially to the optical path length.

[0035] The windows 7, 8 are formed from quartz glass, while the measuring cell body 5 consists of plastic in this exemplary embodiment. The dimensions of the outside contour of the windows 7, 8 and of the inside contours of the guide channels 11, 12 are dimensioned such that the windows 7, 8 at room temperature, therefore at roughly 20 C., can be moved along the guide channels 11, 12 by sliding, even under process conditions, therefore at elevated temperatures, especially greater than 40 C., preferably greater than 60 C., there being frictional engagement between the outside contour of the windows 7, 8 and the respective inside contour of the guide channels 11, 12 so that the windows 7, 8 seal the measurement space 4 relative to the environment even at pressures, especially greater than 3 bar. The tolerance of the fits is made accordingly, the different expansions of the different materials being considered.

[0036] To do this it is advantageously provided as claimed in the invention that the windows 7, 8 have a thickness D which is greater than usual at a ratio to a width B of the windows 7, 8. Preferably the ratio D to B is at least 1:10, especially at least 1:5, preferably at least 1:3, even more preferably at least 1:2.

[0037] It is also conceivable as claimed in the invention to fix the windows 7, 8 after setting of a distance A in the production/ installation of the windows 7, 8 so that adjustment of the windows is precluded. This is especially advantageous when using the measuring cell 1 as a disposable measuring cell.

[0038] In the second embodiment which is made very similarly to the first according to FIG. 2, in contrast to the embodiment as shown in FIG. 1, there is one window receiver 9, 10 each for accommodating the windows 7, 8. The window receivers 9, 10 are made tubular with an inside contour which corresponds to the outside contour of the windows 7, 8 so that the windows 7, 8 are fixed in the window receivers 9, 10. The windows 7, 8 are each fixed in the window receivers 9, 10 on the end of the window receiver 9, 10 which points toward the measurement space 4, especially flush with the window receivers 9, 10. The window receivers 9, 10 with their outside contour correspond to the guide channels 11, 12 such that the above described interaction between the windows 7, 8 and the guide channels 11, 12 applies as in the first embodiment according to FIG. 1. Both the guide channels 11, 12 and the window receivers 9, 10 as well as the window receivers 9, 10 and the windows 7, 8 have a fit to one another. The fit can be made such that mutual displacement is possible for only one of the two fits. Advantageously the two fits can be made movable, as a result of which a larger adjustment range can be implemented.

[0039] By the window receivers 9, 10 on their ends facing away from the windows 7, 8 projecting over the measuring cell body 5 or over the guide channels 11, 12, the adjustment of the distance A between the windows 7, 8 is simplified, especially when the distance A is increased. This is because the window receivers 9, 10 can be gripped on their ends which project above the measuring cell body 5 or the guide channels 11, 12. Using the dimensions of the window receivers 9, 10 along the beam path, the distance A, therefore the optical path length, can be measured and computed and can accordingly be automatically set. In this case it is advantageous if the fit between the guide channels 11, 12 and the window receivers 9, 10 is made movable.

[0040] The statements on the first embodiment also apply analogously to the second embodiment.

[0041] FIG. 3a shows a measuring cell 1 with a measuring cell body 5 which consists predominantly of flexible material, especially rubber. The fluid which is to be measured is routed via an inlet opening 2 into a measurement space 4 and leaves the measurement space 4 via an outlet opening 3 which is shown in FIG. 3b. The inlet opening 2 and the outlet opening 3 have process connections for incorporating the measuring cell 1 into the process line, therefore for inline measurement.

[0042] Transversely to the flow direction of the fluid there is a radiation measurement region 6 in which the interaction of the fluid with electromagnetic radiation is measured.

[0043] The radiation enters the measurement space 4 through a window 7 and emerges from the measurement space 4 through a window 8 which is located opposite. The electromagnetic radiation is produced by a radiation source which is not shown outside the measuring cell 1 and is routed transversely to the flow direction of the fluid through the measurement space 4 and the windows 7, 8. On the opposite side, therefore under the window 8 and outside the measuring cell 1, the radiation is detected by a corresponding measuring apparatus, by the interaction with the fluid along the optical path length between the windows 7, 8 the changes which identify the fluid being detectable.

[0044] An important aspect of detection is the optical path length which exists by a distance A between the window 7 and the window 8.

[0045] One wall 13 of the measuring cell body 5 which is made as a peripheral wall is attached to the side of the window 7 which points toward the measurement space 4, especially in the center of the window 7 there being a passage opening 14 so that the electromagnetic radiation can enter the measurement space 4. A corresponding wall 15 which is made as a peripheral wall and which is located opposite is likewise made flexible. It is accordingly fixed on the window 8 on one side of the window 8 which points toward the measurement space 4 and has a passage opening 16 for exit of the electromagnetic radiation through the window 8.

[0046] The measuring cell body 5 or the measuring cell 1 is fixed by at least one, in this exemplary embodiment two U-shaped spring clips 17, 18 transversely to the flow direction of the fluid. The spring clips 17, 18 extend around the measuring cell body 5 and the windows 7, 8 from the side of the windows 7, 8 facing away from the measurement space 4.

[0047] To fix the distance A between the windows 7, 8 there is at least one, in this exemplary embodiment two spacer pieces 19, 20 which are clamped outside the measuring cell body 5 as rigid spacers between the windows 7, 8, in particular by the clamping action of the spring clips 17, 18.

[0048] Accordingly by replacing the spacer pieces 19, 20 and optionally the spring clips 17, 18 an adjustment range of the distance A which is limited by the shape of the walls 13, 15 can be implemented so that there is a system consisting of a standard measuring cell 1 and a set of spring clips 17, 18 and corresponding spacer pieces 19, 20.

[0049] It is advantageously provided as claimed in the invention that the replacement of the windows 7, 7, 8, 8 is not necessary for adjusting the distances A, A. The spring clips 17, 18 and spacer pieces 19, 20 which are intended for a defined distance A can be understood as sets with defined identifications so that replacement can be managed correspondingly easily.

[0050] The spacer pieces 19, 20 each have one installation opening 21, 22, especially in which the spacer pieces 19, 20 are made as U-shaped sections so that adjustment of the distance A is enabled without decoupling of the measuring cell 1 from the process lines.

[0051] The function of the spring clips 17, 18 according to one advantageous embodiment which is not shown can be integrated into the spacer pieces by the windows 7, 8 being able to be received into the spacer pieces. The spacer pieces can have corresponding receivers, especially plug grooves, on their tops and bottoms.

REFERENCE NUMBER LIST

[0052] 1, 1 measuring cell [0053] inlet opening [0054] outlet opening [0055] 4, 4 measurement space [0056] 5, 5 measuring cell body [0057] radiation measurement region [0058] 7, 7 window [0059] 8, 8 window [0060] 9 window receiver [0061] 10 window receiver [0062] 11 guide channel [0063] 12 guide channel [0064] 13 wall [0065] 14 passage opening [0066] 15 wall [0067] 16 passage opening [0068] 17 spring clip [0069] 18 spring clip [0070] 19 spacer piece [0071] 20 spacer piece [0072] 21 installation opening [0073] 22 installation opening