EP0423125A1

EP0423125A1 - Dynamometric probe for measuring the parameters of a liquid

Info

Publication number: EP0423125A1
Application number: EP89903170A
Authority: EP
Inventors: Milenko Radosavljevic
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-09-07
Filing date: 1989-03-02
Publication date: 1991-04-24
Also published as: WO1990010214A1; FR2620226A1

Abstract

L'invention concerne une sonde dynamométrique particulièrement sensible qui permet la détection de variations de structures moléculaires d'un milieu liquide ainsi que la mesure statique et dynamique, en temps réel, des paramètres physiques, chimiques, biochimiques et biologiques du même milieu. Un bras (4) solidaire d'un fil de torsion (1) porte à une de ses extrémités une palette interchageable (10) ainsi qu'une lamelle obturatrice (12). Le bras (4), sous l'effet moteur d'un dispositif électromagnétique (6, 7, 9), oscille autour du fil de torsion (1). La palette (10) plonge dans le milieu à étudier (22) qui freine son mouvement. Un capteur optoélectronique (13 à 15), comprenant la lamelle obturatrice (12), mesure le déplacement angulaire du bras (4) et délivre un signal électrique, sous forme analogique ou numérique. Les applications concernent toutes les industries et laboratoires traitant les milieux liquides plus au moins visqueux tels l'industrie chimique, la pétrochimie, l'industrie pharmaceutique, l'industrie agro-alimentaire, divers laboratoires d'études et d'analyses médicales ou autres.The invention relates to a particularly sensitive dynamometric probe which allows the detection of variations in molecular structures of a liquid medium as well as the static and dynamic measurement, in real time, of the physical, chemical, biochemical and biological parameters of the same medium. An arm (4) secured to a torsion wire (1) carries at one of its ends an interchageable pallet (10) as well as a shutter strip (12). The arm (4), under the motor effect of an electromagnetic device (6, 7, 9), oscillates around the torsion wire (1). The pallet (10) plunges into the medium to be studied (22) which slows down its movement. An optoelectronic sensor (13 to 15), comprising the shutter blade (12), measures the angular displacement of the arm (4) and delivers an electrical signal, in analog or digital form. The applications relate to all industries and laboratories dealing with more or less viscous liquid media such as the chemical industry, petrochemicals, the pharmaceutical industry, the food industry, various study and medical analysis laboratories or others.

Description

DYNAMO CALIBRATION PROBE FOR MEASURING PARAMETERS OF A LIQUID

The present invention relates to a dynamometric probe intended for the detection, observation and measurement of variations in physical, chemical, biochemical or biological characteristics of a medium to be studied.

The primary object of the invention is to provide an instrument for observation and measurement, in real time, of slow variations in physical, chemical, biochemical or biological parameters of a liquid medium of any viscosity.

The dynamometric probe according to the invention is characterized in that it comprises an oscillating element carried by an axial support defining a pivot axis of this element, a motor device of the electromagnetic type which applies to the oscillating element alternating forces determined for make it oscillate, a braking member in the form of a pallet or a rod which is integral with the oscillating element and which is immersed in said medium, and a displacement sensor which measures the angular displacement of the oscillating element which delivers a corresponding electrical signal.

Thus we measure the resistance that the environment studied opposes to the movement of a palette plunging into this environment. A force is therefore measured by means of a torque applied to the pallet, hence the name of the dynamometric probe.

The dynamometric probe is an instrument whose structure and operating conditions provide it with a sensitivity such that it makes it possible to detect variations in the molecular structures of the medium studied, the causes of which can be of a physical, chemical, biochemical or biological nature. It delivers an electrical signal, analog _or digital, the maximum amplitude of which directly depends on this structure. The signal delivered lends itself to any analog or digital processing, thus allowing qualitative and quantitative analyzes, comparative analyzes as well as statistical analyzes of the processes. - £ - observed. It allows, in particular, the graphical tracing of the evolution of the physico-chemical, biochemical or biological state of the environment studied, tracing which represents the image in real time, of the evolution of this state.

Among the numerous applications, we can cite the trace, in real time, of the enzymatic processes, or else the thromboelastographic trace which, in addition to usual data, provides new data not contained in the HARTERT trace and thus gives these new interest reviews.

If the state of the medium is not changing, the amplitude of the signal delivered characterizes this state under precise physical conditions and can therefore be used to identify this state, i.e. to measure d 'one of the characteristic parameters of this state. Thus, for example, the dynamometric probe delivers a signal whose amplitude is a linear function of the concentration of a solution, under given physical conditions. Calibrated, the probe can therefore constitute an instrument for measuring the concentration of a solution.

The dynamometric probe is thus an instrument for qualitative and quantitative observation of events in a liquid, capable of carrying out both static and dynamic measurements of any parameter characteristic of the environment studied. The applications relate to all industries and laboratories which use or treat more or less viscous liquid or pasty media, in particular the chemical industry in general, the petrochemical industry, the pharmaceutical industry, the food industry, various laboratories. study and analysis, medical and others.

In a particular embodiment of a probe according to the invention, the axial support consists of a twist wire which is fixed at its two ends and which defines the pivot axis of the oscillating element.

The oscillating element can be formed by a rigid arm arranged perpendicular to its pivot axis, the displacement sensor being disposed near one end of this arm. Preferably, the center of gravity of the swinging arm and the motor device are located near the pivot axis, and the braking member is disposed near one end of the arm. The motor device, in a first embodiment, comprises a fixed stator and a mobile magnetic assembly fixed to the oscillating element in a symmetrical arrangement relative to the pivot axis. In another embodiment, the motor device comprises an electric coil in the form of a mobile frame which is integral with the oscillating element and which is in a magnetic field at the intensity of the constant magnetic induction.

The braking member in the form of a cylindrical rod or a pallet is arranged vertically in the liquid medium to be studied and so as to offer maximum resistance to the movement of the oscillating element.

According to a preferred form of the invention, the displacement sensor is an optoelectronic sensor comprising a photo-emitter delivering a constant light flux, a photoreceptor which receives the light flux coming from the photo-emitter and which delivers an electrical signal whose intensity is a direct function of the light flux received, a shutter strip which is integral with the oscillating element and which has the role of closing, depending on the angular position of the oscillating element, the light flux picked up by the photoreceptor. Thus, the photoreceptor delivers an electrical signal at its output, the instantaneous amplitude of which is directly proportional to the light flux received. Alternatively, the photoreceptor can be part of an optoelectronic generator of periodic signals, intended to deliver an electrical output signal whose frequency is a direct function of the light flux received by the photoreceptor. This output signal can for example be a sawtooth signal.

The structure and operation of a probe according to the invention are described below by example embodiments, given without limitation and with reference to the appended drawing, in which:

FIG. 1 is a schematic side elevation view of a preferred embodiment of a dynamometric probe according to the invention, comprising an oscillating arm and an optoelectronic displacement sensor, - if - Figure 2 is a schematic plan view of the swinging arm and its motor device,

FIG. 3 is a schematic elevation view illustrating another embodiment, and

The figure is a simplified electrical diagram of an optoelectronic displacement sensor usable with the probes according to Figures 1 to 3.

With reference to FIGS. 1 and 2, the dynamometric probe comprises a torsion wire 1 with a low torsional constant, fixed at its two ends to a frame 2, 3 so that the tension of the wire is adjustable. A rigid arm made of very light materials is attached to the middle of the torsion wire and perpendicular to it by a fixing device 5. The torsion wire 1 and the arm, located in the same plane, form an integral assembly whose arm can perform a rotational movement around the axis defined by the twist wire 1. Two magnetized pads 6 and 7 of negligible weight are secured to the arm and are arranged symmetrically with respect to the axis of rotation. The distance between the pads 6 and 7 can be provided adjustable in certain applications. In the case of simplified structure probes, a single pad 6 or 7 may be sufficient. Facing the magnetized pads 6, 7, is placed the ferromagnetic core 8 in the shape of a U of an electric coil 9. The coil 9 being supplied with alternating current, the polarity of the magnetized pads _C s oriented so that, when a pad undergoes a force of attraction, the other undergoes a force of repulsion. Thus, to an alternating current of low maximum amplitude corresponds an oscillatory movement of the arm around its axis materialized by the twist wire 1.

At one end of the arm k is fixed interchangeably a pallet 10 of suitable shape, by means of a fixing system 1 1. On the other hand, at a fixed distance from the axis of rotation, on one or the other side of the arm is fixed a strip 12 acting as an optical shutter. One of the edges of the strip 12, parallel to the arm, called the active edge 21, is aligned with the central axis of the arm, an axis which intersects the axis of rotation coincident with the twist wire. A photo-emitter 13 and a photoreceptor 1, the spectrum of which is preferably in the infrared, form a photocouple, and are arranged on either side of the shutter strip 12. The width of the strip 12 must be sufficient to completely block the light beam received by the photoreceptor 14. At rest, that is to say at zero current in the coil 9, the photocouple 13, 14 is positioned relative to the active edge 2 1 of the strip 1 2 so that the photoreceptor 14 receives exactly half of the total light flux received without obturation. The photo-emitter 13 is supplied by a constant current source 1 5. During the oscillatory movement of the arm 4, the strip 12 more or less blocks the emitted beam, which allows, for an intensity of the photo-emitter 13 assumed constant, to collect at the output of the photoreceptor

14 a current proportional to the supposedly small deflection angle of the arm 4. The current of the photoreceptor 14 can be amplified directly by a current amplifier 17, in order to increase the reading sensitivity of the deflection angle of the arm 4.

By introducing a load resistor 18 in series with the photoreceptor 14, it is then possible to collect at the terminals of the load a potential difference proportional to the current of the photoreceptor. As this current is proportional to the angle of deflection of the arm 4, the same goes for the potential difference. In this case, to increase the reading sensitivity of the deflection angle, a voltage amplifier 19 is used. In current applications, the coil 9 is supplied by a source 16 of sinusoidal alternating current at fixed frequency, constant maximum amplitude. but adjustable.

From the above we deduce the functioning of the whole in the observation of physico-chemical or biochemical processes, in a liquid medium. Indeed, the pallet 10 plunges into the sample of the liquid to be studied 22. The arm 4, being subjected to a driving torque due to the sinusoidal forces of constant maximum amplitude which are exerted on the pellets 6 and 7, describes a movement oscillating around its axis of rotation materialized by the wire 1. By means of the pallet 10, the liquid medium 22 exerts a resistive torque which opposes the engine torque and thus limits the maximum amplitude of the angle of deflection of the arm 4. The maximum amplitude resulting from the movement depends on the physical structure or the chemical nature of the liquid medium studied 22 and therefore reflects the relative physical or chemical state of the medium. The photocouple 1 3, 1 4 delivers an electrical signal whose maximum amplitude is directly proportional to the maximum amplitude of the _ é - oscillatory movement of the arm 4. Thus, any variation in the physical state of the medium 22 results in a variation of the maximum amplitude of the angle of rotation of the arm 4 and consequently of the maximum amplitude of the current of the photoreceptor 14 or of the potential difference linked to the latter.

The structure of the probe described above corresponds to an optimal structure which ensures maximum sensitivity and resolving power. Under these conditions, it can be hoped, if sufficient care is taken with its mechanical production, that it will be operational in mediums with very low viscosity and even at the limit usable in mediums in the vapor state or gas of a certain density.

On the contrary, if one does not look for extreme sensitivities of the probe and a fortiori if one is dealing with very viscous liquid media, at the limit even with solids with sufficient elasticity, such as certain food products, meats for example, the structure previously described can be modified to a certain extent. Thus, the torsion wire 1 can be replaced by a rigid axis possibly provided with a spiral spring acting as a return spring, a system similar to the balance spring with a clock.

Similarly, the motor torque of the probe can be achieved by a mobile frame device, similar to the mobile frame of a galvanometer and similarly secured to the twist wire 1 or the rigid axis and the coil of which is supplied by a sinusoidal alternating motor current. The assembly then replaces the magnetized pads 6 and 7 as well as the coil 9 with its core 8.

The optoelectronic displacement sensor described above can be replaced by another type of optoelectronic sensor, illustrated in FIG. 4, also of high sensitivity. The latter comprises an optoelectronic generator 23 of signals, for example sawtooth 24, where the photoreceptor 14 is an integral part of the generator used.

A variation in the light flux received by the photoreceptor 14, due to the movement of the strip 12, causes a variation in the frequency of the signal from the generator 23. Here the result of the reading of the displacement is presented directly in digital form, the benefit , in good of applications, is certain.

As for the structure of the signal generator, it corresponds to the general simplified diagram of FIG. 4 for the sawtooth signals. The operating principle is based on the charging or discharging of a capacitor through a photoreceptor. Considering the diagram, it can be seen that the capacitor 27 is charged through the photoreceptor 14 with a charging speed which is directly proportional to the light flux received. A threshold comparator 29 detects the maximum voltage admitted at the terminals of the capacitor 27 and commands the closing of a switch 2S through which the capacitor 27 discharges, after which the cycle begins again. It is understood that the frequency of the signal delivered 24 depends on the illumination received by the photoreceptor. For some applications, the use of a PIN type photoreceptor may prove useful.

The maximum angle of deflection of the arm 4 can be measured by other means and in particular by means of a potentiometer secured to the rotating mechanical part, thus replacing the photocouple 13, 14 and the lamella 12. The latter solution may be advantageous in the case where we are dealing with very viscous media, even elastic solid media, and where the twist wire 1 is replaced by a rigid axis integral with the potentiometer. This structure ensures great compactness for the entire probe.

The rigid arm 4 consists of two integral branches, of comparable or non-comparable lengths, located on either side of the twist wire 1 or of the rigid axis. The shutter 12 can be arranged on the same side of the arm as the pallet 10 or on the other side depending on whether the arms of the arm are of comparable length or not. FIG. 3 illustrates an embodiment in which the asymmetry in length of the arms of the arm

4 'gives less volume to the whole. In this case the two branches, of unequal lengths, are balanced in mass by a counterweight 20 located on the end of the shortest branch.

For most applications, the shape of the motor current flowing through the coil 9 is sinusoidal. However, a periodic current of rectangular shape or a step of current may be more suitable in certain applications such as studying or measuring the viscosity of particular media. Similarly, a linearly growing current in time can be useful in studying the response of a medium. A person skilled in the art will be able to envisage many other modifications and variants with respect to the examples mentioned above, without however departing from the scope of the present invention.

Claims

claims

1. Dynamometric probe intended for the detection, the observation and the measurement of the variations of physical, chemical, biochemical or biological parameters of a medium to be studied, said probe comprising:

- an oscillating element (4, 4 ') carried by an axial support (1) defining a pivot axis of this element,

an electromagnetic motor device (6 to 9) arranged to apply to the oscillating element a determined torque to make it pivot around its axis,

a braking member (10) in the form of a pallet or a rod integral with the oscillating element and which plunges into said medium (22),

and a displacement sensor (12 to 19) measuring the maximum amplitude of the angular movement of the oscillating element by delivering a corresponding electrical signal, characterized in that the oscillating element comprises an oscillating arm (4, 4 ') arranged transversely to its pivot axis, and in that said braking member (10) is mounted on this arm and is spaced from the pivot axis

2. Probe according to claim 1, characterized in that the axial support comprises a twist wire (1) which is fixed at its two ends and which defines the pivot axis of the swing arm.

3. Probe according to claim 1 or 2, characterized in that the displacement sensor is arranged near one end of this arm.

4. Probe according to claim 3, characterized in that the center of gravity of the swinging arm (4, 4 ') and the motor device are located near the pivot axis (1), and in that the member brake (10) is disposed near one end of the arm.

5. Probe according to one of claims 1 to 4, characterized in that the motor device comprises a fixed stator (8, 9) and a mobile magnetic assembly (6, 7) fixed to the oscillating arms in a symmetrical arrangement with respect to the pivot axis.

6. Probe according to one of the preceding claims, characterized in that the braking member in the form of a cylindrical rod or a pallet (10) is arranged vertically in the medium of the liquid to be studied (22) and so as to offer maximum resistance to the movement of the swing arm (4, 4 ').

7. Probe according to one of the preceding claims, characterized in that the displacement sensor is an optoelectronic sensor comprising a photoemitter (13) delivering a constant light flux, a photoreceptor (14) arranged to receive the light flux coming from the photoemitter and to deliver an electrical signal whose amplitude is a direct function of the light flux received, and a shutter strip (12) which is integral with the oscillating element (4, 4 ') and which has the role of closing, depending from the angular position of the oscillating element, the light flux picked up by the photoreceptor (14).

8. Probe according to claim 7, characterized in that the photoreceptor (14) is part of an optoelectronic generator of periodic signals (23), intended to deliver an electrical output signal (24) whose frequency is a function direct light flux received by the photoreceptor.