DE102017003478B3 - Magnetic stirrer with sensor - Google Patents

Abstract

In stirrers with stirrer and stirring (stirring) of the stirring body has the closest contact with the medium to be stirred and is therefore predestined as a location for a sensor for detecting a parameter of the medium to be stirred, for which, however, the sensor data from the rotating stirring body on the stationary side are transferred. Some very interesting sensors and sensor techniques (resonant sensors, SAW, etc.), along with the associated electronics, can be miniaturized in the prior art so that they can be integrated into the stirring body. However, the sensors often work with very high signal frequencies, which would even be suitable for the wireless transmission of sensor data in the airspace. But this does not work inside a liquid or in the presence of metallically conductive materials. The transmission of energy and data to supply the sensors with electronics, the use of high frequencies in sensor functions (eg SAW sensors) and the provision of data transmission from the stirring body to the outside require different technical measures. Under the use of a pulse width modulation, the energy and data transmission ensured low frequency to the agitator; using digital beating, sensor data are provided at low frequency and thus transmitted to the outside from the stirring body; the sensor function can operate at any desired high frequency because it is generated and used in a restricted manner on the stirring body. The use of sensors operating with high-frequency signals (for example SAW sensors) is also possible in a liquid medium or in a metallic environment.

Description

The invention relates to magnetic stirrer with a (essential device functions encapsulating) housing (hereinafter referred to as the device base or base unit), which up to the application level of the magnetic stirrer has a possibly heated Aufstellplatte and in the means for generating a variable-rotational magnetic field as a drive are present for a stirring body, which is inserted into the medium in the container set up on the mounting plate and, driven by the variable-magnetic field, the medium is stirred. The device also has means for controlling and / or controlling and / or monitoring internal or external (also application-related) physical and / or chemical parameters. Parameters of internal and external sensors are provided via suitable interfaces. For the detection of physical parameters, the device can also have electronics in addition to sensors, which is referred to here as a control unit and used as such.

Prior Art 1: Magnetic stirrer

Such magnetic stirrers are known in various forms and configurations, with individually and / or repeatedly present vessel installation positions or vessel positions for the stirring medium (s), with a (heatable or non-heatable) mounting plate. These devices often have additions or special additional functions, such as special interfaces, heated mounting plates, weighing devices, temperature measuring devices, etc. To increase the stability of a flat design of the device is advantageous. Basic design features of stirrers are a drive unit and an interchangeable mixing tool and the same handling (choose stirring tool, connect this with the drive unit, dip the stirring tool into the medium, stir). With the patent literature it must be proved that innovations can affect both elements (drive and stirring tool) together and separately (eg DT1557230C3 (1967)) "stirring part for a magnetic stirrer"). In the case of sensors, transponder constructions and, in particular, the use of SAWs in the case of airspace transmissions are generally known and used (eg DE 2916078A1 (1979)).

The use of a SAW sensor is known in the prior art: an input (eg piezoelectric material) on the input side lying interdigital transducer (IDW) converts an electrical signal into a surface acoustic wave that passes over the substrate and at the end of a signal path of a output side lying second interdigital transducer is converted back into an electrical signal. The necessary materials and techniques are known; Such sensors are freely available. In order to keep the designs of these sensors reasonably small, the frequencies to be used must be very large (in general above 10 MHz, far into the GHz range).

The operation of a magnetic stirrer is characterized in that inside the device base coils or (driven by a primary drive) rotating drive magnets generate a variable-rotating magnetic field. The rotationally variable magnetic field is via a magnetic force coupling the drive for a stirring body (a stirring magnet, stirring, eg a simple stirring rod), which is inserted into the medium in the erected vessel and is thus placed in rotating motion and thereby the medium is stirred, the Medium additionally via a heater, eg can be supplied by a heated mounting plate, heat energy.

Since there is a certain distance between the drive magnet (or the coils) due to the construction, the force for driving the stirring body is limited, so that only low-viscosity media can be stirred.

The stirring body itself may be sensors or sensory elements and electronics for determining physical, chemical, biological and / or other parameters (here especially in the (generally liquid) medium) and / or additionally coils and antennas for receiving and / or providing energy and / or or for the transmission of data and / or additionally have means for storing energy and / or additionally having electronic circuits. This opens up new areas of use for the magnetic stirrer.

However, when a sensor is connected to a rotating (stirring) part, data must be transferred to the stationary side of the stirrer (i.e., the user side). For this purpose, contact (e.g., slip rings) or wired and wireless methods are known, e.g. Radio interfaces, which include u.a. also transponder constructions belong.

From the DE4440250A1 is a "magnetic stirrer" of the type mentioned above, in which the determination of physical, chemical and / or biological parameters is specified. Energy and data can be transmitted via the magnetic field between the stirrer and the measuring electronics. As operating frequency frequencies up to the gigahertz range are preferably specified to 135 kHz. The measuring electronics including all sensors (in the stirring body) can form a functional unit in a housing.

Innovations in the field of magnetic stirrers can, independently of one another, principally relate jointly and / or separately to the two always present main components stirrer drive (part of the ever-present base unit) and stirrer, which here is in the form of the stirrer body (eg DT1557230C3 "stirrer for a magnetic stirrer") , but also certain functionalities or specific applications of a magnetic stirrer.

In order to be able to provide additional functionalities for applications of such magnetic stirrers, additional technical components are often required, which are often only a provision of functional additives independent of the magnetic stirrer (if and because the functional additive can also be used independently of a magnetic stirrer and can also be used without a magnetic stirrer, eg a PH meter, as long as the components of the additional functionality need not be connected to the magnetic stirrer base unit). The use of an additional device provides the user of a magnetic stirrer i.a. but always an additional handling effort.

As a result, additives are often found as pluggable or attachable additives. From the DE2144372A (1971), for example, "devices without heating, with heating and additional facilities for the measurement of certain physical quantities in the stirred liquid" are known, wherein "the electric heater is designed as a self-contained, removable from the housing component with the upper parking space for the vessel" ,

A heating device (29) (cf. ) as an additional function for a magnetic stirrer can thus be provided as an integral part of the magnetic stirrer or can be considered and designed as a separate, at least removable component of the magnetic stirrer.

Additional functionality may also be provided e.g. by the design of the stirring body (e.g., triangular or round shapes).

To control a temperature, additional means for influencing the energy supply to the heating device must be provided in the device. This i.a. Electronic means should be referred to collectively as "electronic control".

A "control" takes place here in the sense of the process sequence "observation of an actual value, the detection of deviations from a setpoint and influence on a manipulated variable in order to change the actual value in the direction of the setpoint". As a manipulated variable is here in particular a PWM control as part of a regulatory procedure in the focus of the considerations. The methods used for a control itself are i.a. analog and / or digitally operating control method.

It may be useful to monitor only the temperature of the stirring medium in order to set and / or regulate a temperature exactly. The temperature to be set does not necessarily have to be measured at a defined point, but can be measured equivalently at any point on the heat transport path, from the heating element via the mounting plate, via the material of the Aufstellgefäßes, in the medium or outside, provided that the transport operations can be specified as stable ,

Sensors are present in large numbers in the state of the art, use various technologies for detecting physical, chemical, biological or other variables and can be miniaturized in the state of the art, together with necessary electronic circuits, to such an extent that sensor arrangements and the like may be used. can also be installed directly in a stirring body.

Since the stirring body is in the medium, that is, where the immediately strongest mixing takes place by the stirring and the stirring body is in direct contact with the medium, or the mixing is very effective, because for the medium present in the vessel, the mixing movement there has its origin, a suitable sensor attached directly to this agitator can detect a physical parameter very rapidly (possibly just changing) and effectively (because it is directly at the site of the most efficient mixing action).

The electronic control can i.a. may also be further used to control and / or control and / or monitor other parameters or may be adapted to other tasks and / or may include other application-related, external and / or internal physical and / or chemical parameters, e.g. process or monitor in the medium in the container.

In order to be able to regulate and / or control and / or monitor, appropriate sensors must be provided in the respective control concept, which may possibly also be positioned outside the housing, eg in the vessel with the medium. In order to make the necessary parameters for controlling and / or controlling and / or monitoring accessible to the electronic control, means for wired or wireless data transmission and / or energy transmission, also via the Limits of the housing of the device base away, be present.

The invention described here can be used in all known with magnetic stirrers drive forms, but may u.U. be modified in the context of the respective drive form.

Prior art 2: Magnetic stirrer drive

• - unter der Aufstellplatte angeordnete, elektrisch versorgte und elektronisch gesteuerte Spulen als reiner Magnetspulenantrieb ( ),
• - von einem Motor als Primärantrieb rotierend angetriebene (i.W. länglich orientierte) Antriebsmagnete ( ), die
  • ○ in Längsrichtung magnetisiert sind,
  • ○ deren Rotationsachse
    • ■ senkrecht auf dieser Magnetisierungsrichtung steht und
    • ■ parallel zur Rotationsachse des Rührkörpers liegt (i.W. mit dieser sogar übereinstimmt),
  • ○ deren Rotationsebene
    • ■ parallel zur Rotationsebene des Rührkörpers liegt,
    • ■ die i.W. parallel zur Aufstellfläche liegt,
  sowie
• - von einem Primärantrieb angetrieben rotierende (mehrere, hier vier) Antriebsmagnete ( ), die
  • ○ in Querrichtung magnetisiert sind,
  • ○ deren Rotationsachsen
    • ■ senkrecht auf der Magnetisierungsrichtung stehen und
    • ■ senkrecht zur Rotationsachse des Rührkörpers stehen,
  • ○ deren Rotationsebenen
    • ■ senkrecht zur Rotationsebene des Rührkörpers liegen.

As means for generating rotationally variable, strong magnetic fields which are intended to drive the stirring body in the medium, in the prior art ( ) known:

• - Under the mounting plate arranged, electrically powered and electronically controlled coils as a pure magnetic coil drive ( )
• - Driven by a motor as a prime mover driven (iW longitudinally oriented) drive magnets ( ), the
  • ○ are magnetized in the longitudinal direction,
  • ○ whose rotation axis
    • ■ is perpendicular to this magnetization direction and
    • ■ is parallel to the axis of rotation of the agitator (iW even coincides with it),
  • ○ its rotation plane
    • Is parallel to the plane of rotation of the stirring body,
    • ■ the iW is parallel to the footprint,
  such as
• - Driven by a primary drive rotating (several, here four) drive magnets ( ), the
  • ○ are magnetized in the transverse direction,
  • ○ their rotation axes
    • ■ are perpendicular to the magnetization direction and
    • ■ are perpendicular to the axis of rotation of the stirring body,
  • ○ their rotation planes
    • ■ lie perpendicular to the plane of rotation of the stirring body.

In this state of the art, these three basic forms of drives represent the type of magnetic stirrers that are in focus here: the axes of rotation (1) and the stirrer levels (3) of the stirring body (2) are due to the same function of each magnetic stirrer All forms are represented equal (and are therefore also referred to in the sub-images la-c also equal). The stirring bodies (2) themselves also have a magnet and rotate (coupled to the rotationally variable magnetic field of the drive) about their axis of rotation (1) in the same direction (3). The magnetic poles of the stirring body and the drive magnets are indicated with an N (for north pole) and S (for south pole). In the following, all the magnets which serve to drive this stirring magnet (which is connected to the stirring body) should be referred to as "drive magnet (s)", the magnet in the stirring body as "stirring magnet".

For pure coil drives ( ) is generated by a suitable control (5) of the coils (4) in the device base, a rotationally variable magnetic field, which aligns the stirring magnet and he can follow, whereby he is placed in the medium in rotating motion and the medium stirred. Because the field strength of permanent magnets by means of coils is difficult or can be achieved only with great effort, a relatively high technical and energy costs is necessary.

For the "usual magnetic stirrers" (see Fig.lb u. left in side view, right in top view; with the same designators for the same details), a usually elongated drive magnet (7) is used, whose magnetization takes place in the direction of its length (the magnetic poles N and S are located at the ends of the drive magnet (7)). Force-coupled to the magnetic field, the stirring body (2) inserted in the medium rotates with the drive magnet (7), generally by a certain angle (12) (see FIG. ) offset with. The stirring body (2) is designed as a magnet (with north and south pole) or contains such a permanent magnet (stirring magnet) and rotates with the rotation of the drive magnet (7), parallel to the work surface or to the mounting plate (29) or to the footprint ( 10). The axis of rotation (8) of the drive magnet (7) and the axis of rotation (1) of the magnet of the stirring body (2) lie parallel, and in some cases even coincide. Connected via the rigid coupling of a drive shaft (9) with a motor (6), the drive magnet (7) is driven.

A parameter acquisition for a control (for example, the temperature measurement for a temperature control) can therefore also be carried out directly in the medium itself and e.g. be provided as part of or task of the stirring body, but this requires a transfer of energy and / or data between the base unit and the stirring body.

To the last kind of to described three drive forms for a magnetic stirrer (Fig.lc) is on the DE102014004705B3 directed. This document is to be taken from a magnetic stirrer drive construction, in which the drive magnets, which are also magnetized transversely to its axis of rotation, not parallel to the work surface and not parallel to the Rotate the rotation plane of the stirring magnet. However, the force coupling between the stirring element (stirring magnet) and the driving magnet driving the stirring motion is in this case also the force-exchanging interaction between two strong permanent magnets (ie more efficient with respect to a coil drive). Here, however, this drive has the potential for greater force development compared to a "conventional magnetic stirrer", because the distance between the magnets can be kept smaller.

Arrangements according to this DE102014004705B3 may in particular be such that their axes of rotation iW, such as shows, from the axis of rotation of the stirring body (ie from the inside) away, pointing radially outward. The axes of rotation (15) (16) (18) (19) of these drive magnets (14) are thus perpendicular to the axis of rotation (1) of the stirring body (2); the planes of rotation of the (four) drive magnets (14) are perpendicular to the plane of rotation of the stirring body (1). One to the footprint (55) (s. ) to be considered circle (54) or the circular area (or circle plane) is divided by the (four) drive magnets (51) (52) (56) (57) in four equal quadrants. Along the axis of rotation of a drive magnet (viewed from the outside in the direction of the central axis of rotation (1) of the stirring body ( )) all drive magnets have the same direction of rotation. With the rotation of the driving magnets (51) (52) (56) (57), a strong rotationally variable magnetic field is produced, followed by the stirring-body magnet (2) (50).

Since the motor-driven "usual magnetic stirrers" (see Fig.lb), the rotating movement of a drive magnet (7) in a plane parallel to the worktop and thus parallel to the mounting plate (29), for which the freedom of movement of the drive magnet (7) In the entire plane (with at least the thickness of the drive magnet (7) and up to the radius of the drive magnet), parts of the axes of rotation (15) (16) (18) (19 ) formed quadrant free. (see, eg, or )

The plane in which the drive magnet moves in the case of the "usual magnetic stirrers" does not have to be kept free as a passage space for the rotational movement of one drive magnet (7) and can be used - at least partially - for new functionalities of the magnetic stirrer.

As already stated, the invention described here in all the above-mentioned drive forms according to (ac) can be used, but may need to be adapted constructively to the respective conditions thereby given. The invention will be described below especially for the above-described drive form according to be described, but without thereby the possibilities of the invention are to be limited thereto.

will be used below to illustrate solutions according to the invention, but is still further abstracted from a real version. The stirring body ( , (50)) will now ( ) no longer or only if necessary shown. To each of the four drive magnets (30) (31) (32) (34) with the four radially outward rotation axes (30a) (31a) (32a) (33a) are the rotational movements (30b) (31b) (32b) ( 33b) indicated. The circle shown (34) is more to be seen as a guide, because as a constructive feature. This circle may represent an imaginary demarcation, but may also be a vessel contour in the plan view, the vessel interior (36) may contain a medium to be stirred or may just be the (possibly further outward) boundary of a heating or mounting plate.

The rotational movements (30b) (31b) (32b) (33b) about the axes of rotation (30a) (31a) (32a) (33a) are in the same sense in the sense that when viewed along the rotation axes from the outside to the inside perpendicular to the illustration standing rotational axis (35) of the stirring body, the directions of rotation are the same in each case (in shown on the left). shows the structure in question again in a perspective view.

In this type of drive of a magnetic stirrer, with remaining surfaces over the quadrants formed by the drive magnets, there are further possibilities for implementing additional functions, in particular for use of sensors, but also for the installation of suitable signal transmitters (for electromagnetic fields, sound, ultrasound, light , Impulse exciters, etc.), which are to be subsumed below under "Actuators".

The drive magnets (51) (52) (56) (57) of the respectively. should be in inside the cross-shaped square protective sheath (72). By way of example, a drive magnet (51) is shown laterally, another drive magnet (57) visible from the front (dashed line). The rotation axis (66) of the drive magnet (57) visible from the front carries out a rotation marked (66) here. A drive coupling for the drive magnets (not shown) is to think in the crossing region of the four-edged protective sheath (72).

As an example, in the free area of one of the quadrants a resistance heating element (70) is indicated (the same in all quadrants, immediately lying under the mounting plate (73) would be interpreted).

As a further example of the use of the free spaces of the quadrants, a coil (77) (e.g., a toroidal coil) is indicated which can be installed in the mounting plate (73) up to the footprint. This coil (77) can be used for different purposes, e.g. for an induction heating, or for an inductive coupling to a sensor element in the interior of an erected vessel, or as a sensor for detecting the Rührkörperlage, etc.

An "other functionality" is indicated abstractly by an element (78). This can e.g. be a force transducer for weight determination or a microphone as a sensor for receiving sound or ultrasound or a light sensor for detecting light, etc.

Three or four similar force transducers (78), positioned in the free quadrant surfaces, can very accurately detect the deployed weight without having to drag the weight of the device base as an offset (resolution-reducing in the weight determination). Sound or ultrasound may e.g. used for filling level and / or weight determination or for other sensory tasks; Light (of different wavelengths) may be used for fluorescence measurements or for others, i.a. also spectral resolution optical measurements are used, etc.

Light or sound may be applied in a first quadrant and in another - e.g. opposite - second quadrants are sensory detected. This allows various new, also term-determining applications and measurements in the medium of standing on the mounting plate of the magnetic stirrer Aufstellgefäßes. Light of a certain wavelength can be selected by choosing e.g. replaceable optical filter can be used selectively. An optical interface on the magnetic stirrer can supply or remove light for spectral measurements. Certain applications may be preliminarily provided by suitable connection points.

A backing plate (74), (e.g., a board on which the entire electronic control can also rest) can support all relevant electronic and mechanical components. A motor (pancake, pancake motor, or the like) may be disposed between the support plate (74) and a bottom plate (75).

The overhead mounting plate (73) can be made interchangeable attachable (together with provided actuators and / or sensor elements or with openings for actuators or sensors that are on the board (74)). Thus, magnetic stirrers with identical drive design and complete, possibly nachprogrammierbarer electronics (FPGA, microcontroller, etc.) can be retrofitted with almost any functionality, which is to be seen as an essential, inventive element, the application cost-effective to be implemented PWM-controlled control loops.

Coils (77) provide general interesting applications. Even larger coils can be easily positioned in the free area of the quadrant and directly under the mounting surface. For drives according to (Coil drive) are already coils, but for which control and possibly the mechanical positions would have to be changed; for drives according to ("Otherwise usual magnetic stirrer") are ia additional coils, especially coils larger design, only with an additional large design effort and an increased distance between the drive magnet and stirring magnet to bring. In accordance with described drive the free space in the quadrant for functional accessories, especially for wireless communication with inductive coupling or power supply of sensor elements, even within a medium, can be used easily.

In order to be able to connect and display the functional additions described in more detail below with a PWM control that is equally possible for all drive types in all devices, the following describes the characteristics of a PWM signal in more detail:

Basics: PWM (Pulse Width Modulation)

Due to an otherwise significant undesirable heat development switching controls (two-step controller) are often used in modern regulations, the performance (voltage, current, etc. in the following only power) only completely or not switch further. Since with such a switched-on power, ie with the switch closed, although a very high current flows, but there is practically no voltage across the closed switch, the amount of heat produced by the switch remains small. If the power is not switched on, there may be a very high voltage across the (then open) switch, but since no current flows, the amount of heat produced by the switch is again only very small. Only in the transition, during ongoing switching operations, as long as neither the current nor the voltage across the switch are zero, losses can occur which translate to a significant extent at relatively high frequencies in heat. The actual power delivered to the respective consumer is only determined by the easily adjustable ratio of pulse duration to pulse pause Process called Pulse Width Modulation (PWM). The switches used are electronic switches (eg FET, MOSFET, IGBT, etc.).

By "PWM ratio" is the ratio of _pulse T (%) T to _period (3%) is understood here and as the quotient value T _pulse / T _period (in the range from 0.0 to 1.0) or as a percentage of T _pulse / T _period * 100 (0% -100%). Without this causing misunderstandings, in this sense "PWM" is also used directly as a variable for this relationship. PWM = 50% or PWM = 0.5 is unambiguous in this sense for a PWM ratio and for a PWM variable value of 0.5.

• - bei fester Frequenz
  • ○ durch Variation der Pulsdauer (mit daraus sich ergebender Pulspause) oder
  • ○ durch Variation der Pulspause (mit daraus sich ergebender Pulsdauer)
  erfolgen, oder
• - bei variabler Frequenz
  • ○ durch Variation der Pulsdauer (bei fester Pulspause) und/oder
  • ○ durch Variation der Pulspause (bei fester Pulsdauer) und/oder
  • ○ durch Variation sowohl der Pulsdauer als auch der Pulspause
  erfolgen,
• - wobei der letzte Fall auch als Frequenzmodulation ausgelegt werden kann.

A PWM setting for a control can

• - at fixed frequency
  • ○ by varying the pulse duration (with resulting pulse pause) or
  • ○ by varying the pulse pause (with resulting pulse duration)
  done, or
• - at variable frequency
  • ○ by varying the pulse duration (with fixed pulse pause) and / or
  • ○ by varying the pulse pause (with fixed pulse duration) and / or
  • ○ by varying both the pulse duration and the pulse pause
  respectively,
• - The last case can also be interpreted as frequency modulation.

shows spectral characteristics of the first frequency components in PWM signals with a fundamental frequency f ₀ and first harmonics f ₁ = 2 * f ₀ (91) and f ₂ = 3 * f ₀ (92) depending on the respective PWM ratio. The determination of these frequency components is carried out from the theoretically predetermined function, as is known, by means of Fourier transformation or, in the case of a real PWM signal function, by means of a frequency analyzer.

The magnitude of the amplitudes and the phase position of the respective frequency component vary in each case depending on the PWM setting: The course of the first curve (90) represents, for example, the amplitude of the fundamental frequency component with the frequency f ₀ in the PWM signal, if a certain PWM ratio is given (plotted on the abscissa from 0 to 1, PWM = 0 and PWM = 1 will not occur, however, because a pulse duration = 0 or a pulse break = 0 should be meaningless for real PWM applications). With this curve (90) comparable to interpret, shows also the resulting at a defined PWM value amplitudes to the frequency components f ₁ = 2 * f ₀ (91) and f ₂ = 3 * f ₀ (92).

With a PWM ratio of 0.5, the frequency components f ₀ (fundamental frequency) and f ₂ = 3 * f ₀ with a maximum possible amplitude are present in a given PWM signal, while f ₁ = 2 * f ₀ is absent. Right and left, still relatively close to PWM = 0.5, the amplitudes of f ₀ and f ₂ decrease, initially only slightly. Additionally, with a PWM setting close to 0.5, the frequency f ₁ = 2 * f _{0 is} added; to the right and left of PWM = 0.5 off fast rising.

This applies in general: The fundamental frequency component and all possibly additionally contained in the PWM signal components with the frequencies 2f ₀ , 3f ₀ , 4f ₀ , etc., have a dependent on the respective PWM ratio amplitude.

By changing or varying the PWM ratio, electronics in the device base can thus generate and / or specify signals with varying spectral components in a targeted manner, without requiring an additional technical measure with the corresponding expenditure for the generation. If e.g. If the coils already introduced above are supplied with such a PWM signal, the illustrated characteristics of the PWM signals can be used for a wireless connection to a sensor element in the interior of the vessel.

Since the frequency f ₀ always exists in the respective PWM signal, this frequency is suitable in particular for energy transmission or for broadcasts (non-specific transmissions to all secondary receivers located in the reception range). The use of other frequencies (f ₁ , f ₂ , ...) depends on the application. Preferred or meaningful PWM values generally result from additional requirements; eg use of the range of zero points in the frequency curves (eg at PWM = ⅓, ⅔, ½, ...) and / or the requirement for amplitude equality (eg at PWM ≈ 0.42 / 0.58 for f ₁ and f ₂ ), etc.

An additional phase shift, which results from a symmetrical transition from PWM = 0.5 + δ to PWM = 0.5-δ when switching back and forth by inverting the PWM signal, can be used for a quasi-analogue transmission of values. A first data channel may e.g. an ASK modulation, a second use a phase modulation. The transmission and / or transmission of certain frequencies can be supported on the primary or transmitter side by adding corresponding filters or resonators.

On the secondary or receiving side, a decoupling to the power supply (not necessarily but preferred) takes place on the frequency f ₀ and can, for example, provide the secondary side required energy for electronics. Because the amplitude of f ₀ to the right and left of PWM = 0.5 decreases relatively slowly, this transfer of energy can be made under largely stable conditions, even while changes in the PWM ratio are being made; at least as long as no small PWM values are required or necessary otherwise. At the same time, broadcasts in the form of phase jumps are searched for and expected (Manchester encoded), alternatively at the frequency f ₁ .

If these frequencies are not generated by the primary, the corresponding function can not be provided, which i.a. but without security-relevant consequences remains. Devices with or without intended PWM-related additional functions can cooperate fully with stirrers with or without special sensor function.

It should be noted that the frequency responses with respect to PWM = 0.5 are symmetrical, i. the spectral amount shares are the same on the right and left of 50%, but of course have a different phase. This can be used additionally or alone for a phase modulation. The phase change can also be used to increase the security of current ASK data transmissions as a redundant channel.

In addition, it should be noted that PWM signals, which are right and left of PWM = 0.5, may be caused by inversion apart. Directly when switching the frequency components show an additional phase jump. This switching inversion may e.g. can be achieved by software (with a microcontroller), but can also be achieved only with a single XOR gate (a data input and a PWM signal input).

Other considerations result in additional use potential: If, for example, 62.5 kHz are selected as the PWM frequency (fundamental frequency f ₀ = 62.5 kHz), then f ₁ = ₂ f _{0 =} 125 kHz results in a typical RFID frequency. The device can then communicate with available transponders on this frequency. Data can be transmitted from the device with f ₁ = 125kHz ASK modulated; Data from the transponder can be passed back to the device through load modulation. Thus, tasks such as accessory detections can only be accomplished using a PWM control. By means of a transponder, eg installed in the stirring fish or applied on the vessel (eg glued on) or imprinted, the base device can recognize and / or retrieve a process profile requested with it, etc.

The above-listed attachable additives may e.g. so contactlessly recognized and taken into account by the control of the device base (accessory detection, process assignment, etc.).

A frequency selection for the PWM signal of 31.25 kHz or 62.5 kHz is in an area in which an induction heating can be operated. This can be operated in combination with other applications in addition to a normal heating, even for an extending through glass vessels into the medium, also possibly replaceable attachable induction heater. About the same, provided for an induction heater coil (77) (see. ), transmission of power and data to an external sensor unit may occur.

In general, it is advantageous to place the power supply for a secondary circuit (sensor) in a frequency range in which a high energy dissipation is allowed and the communication to harmonics in a higher frequency range, but with lower energy, via the PWM ratio control and / or settle adjustable.

In the quadrant spaces, in which, as shown above, heating elements (70) may be located directly under the mounting plate additionally provided for other purposes (not for heating purposes) provided coil (77). With this, a magnetic field that forms in the direction of the vessel to be established, can be generated. The coil (77) can be designed by using a shell core so that the possibly very strong magnetic field generated by this coil is not forwarded downwards and not laterally towards the drive magnets, i. The design can be made so that the magnetization of the drive magnets or the stirring magnet is not lost by the magnetic alternating field of the coil.

In the given context electromagnetic fields with these frequencies (eg 30kHz, 32.5kHz, 50kHz, 62.5kHz, 100kHz) also have the advantage that they penetrate conventional materials and liquid media (in glass vessels and through the glass of the glass vessels) without much attenuation can. Suitably designed and PWM-controlled, this coil (77) can thus be used as an excitation coil not only for an (inductive) supply to the electronics in the stirring body.

Prior art 3: Sensors

In the prior art, sensor elements, together with the respective necessary electronic circuits and structures, can be miniaturized very far, but often very high frequencies must be used.

Specifically, due to the underlying measurement principle, SAW sensors not only allow to capture the one special parameter "temperature", but, going far beyond that, can also be used for the determination of other physical, chemical, biological, etc. parameters. SAW sensors for the detection of pressure, masses, etc. are also state of the art, such as a (at least in a free space transfer) connected remote query, even with a possibility of identification of the individual sensor Among other publications show especially dissertations in recent years, the most diverse applications SAW sensors. For example, SAWs are described as particularly sensitive biosensors: so-called markers, which are applied to the surface of a (piezo) material, to which can bind very specific biomolecules, help to detect the presence of molecules to be detected by the fact that the surface acoustic wave properties of a SAW sensors change when biomolecules attach to these markers. Highly specific sensors can be manufactured in this way.

The monitoring of chemical parameters and processes, even directly in a medium to be stirred, is possible in this way and under certain conditions and can be used in the context of the invention by a suitable referencing. This does not necessarily require the use of a SAW sensor, but can be made particularly sensitive with such a sensor.

The sensor elements and effects used for a temperature measurement are so varied that it does not matter which particular sensor technology is used in each case, especially since such sensors, e.g. as easily used commercially available components, often can not be recognized from the outside, based on which physical principle of the respective sensor module. Temperature dependent materials and / or physical effects produced by means of an i.a. collectively referred to as "sensor array" evaluation (ia electronic) of a metrological detection directly (eg resistors, capacitances, inductances, voltages, currents, etc.) or indirectly (eg over the life, speed of sound, material expansion, quartz frequencies, radiation, etc.) accessible can be used for this purpose.

For temperature measurements in a harsh or inaccessible environment, more generally in situations where temperature data must be transmitted wirelessly to an evaluation unit, various transponder designs are used in the prior art. Type and technique of this possibility are known. As an example of such transponders, constructions for acquiring temperature data, in particular using SAWs, are known which, among other things, enable temperature remote queries also into or out of a harsh and / or dangerous environment ( DE2916078A1 ). However, these can only work if the wireless connection is to be made via a free space route (air); the use of the same technique in liquids is generally not possible.

Due to structurally necessary conditions (structure) and the necessary additions for the excitation, for the evaluation and also for a wireless transmission, which are not optional, but simply necessarily provide when using SAWs (eg the interdigital transducer), such constructions (im Particular in a passive embodiment) are not simply mounted in a liquid (to be stirred) medium on a stirring body and used.

From the already mentioned DE4440250A1 a magnetic stirrer is known which induced by the magnetic field of the stirring device, an electrical voltage for power supply for the measuring electronics and the associated components in the stirring body, such as memory, sensors, etc. Among other things, the frequency mentioned there is 135 kHz, a frequency that can still be used without restriction in the given context. On the magnetic field (in addition to the thus realized drive function) so both the operating energy for the measuring electronics, as well as data transmitted to this stirring body in which the measuring electronics form a functional unit with all sensors and the stirring magnet and are arranged together in a housing. Surface wave resonators, resonant sensors, piezo sensors, frequency-analog sensors, in particular SAW sensors are used in this DE4440250A1 not described

From the DE102012008611A1 and the DE102013010275B3 magnetic stirrers are known in which temperature sensors ( DE10201200861 1A1 ) and especially SAW sensors ( DE102013010275B3 ) should be located on a stirring magnet in the stirring medium immediately above a heated mounting plate. The stirring magnet located in the vessel or container in the medium to be stirred should have a SAW sensor there, which is directly connected to an antenna (coil with inductive coupling) wound longitudinally around the stirring magnet. The core material of the stirring magnet should be wrapped lengthwise, thus form a "loop", thus represents an inductively operating antenna. Such in the longitudinal direction to the elongated, generally round rod magnet wound antenna coil can in the medium about the longitudinal axis of this rod Rolling magnets free and pointing an unclear, over and over again changing, random spatial reference, whereby a connection to another antenna is random, is interrupted again and again and can only be made or exist for a short time. Immediate proximity to a liquid and / or metal, a magnet material as a coil core (for the lengthwise wound stirring magnet), etc. also present problems when the signals to be transmitted for the SAW sensor contain higher frequencies.

For small frequencies, it is known that the spatial dimensions of SAW sensors become very large, so that SAW sensors i.a. are designed for frequencies above 10 MHz (up to the GHz range). Should or must be used a SAW sensor, which can only use signals with a high or very high frequency due to a small size required, are obviously in addition to appropriate measures inevitable. In the context of a magnetic stirrer and with a stirring body, which works as a sensor in liquid, so in a problematic for radio communications or high frequencies, there is thus the general problem that the connection between the base unit and sensor are not operated at a high operating frequency can, but the sensor functionality requires or requires one.

task

In the illustrated technological environment, the object of the invention is for sensory tasks in connection with the use of magnetic stirrers, in which arbitrarily positioned sensors that use or require high-frequency signals and which may also be present in the interior of the medium in a prepared vessel, both a Provide supply for an electronics connected to the sensors, as well as to ensure a data exchange between these sensors and an electronic control in the base unit, in which the disadvantages presented above are no longer present.

This object is achieved with the characterizing details of claim 1.

• - für eine induktive Übertragung von Energie und Daten im Basisgerät dicht unter der Aufstellfläche liegende Spulen konstruktiv vorgesehen sind, und dass
• - über diese Spulen auf einer relativ niedrigen Frequenz mittels eines PWM-Signal, das von der elektronischen Steuerung im Basisgerät eingestellt bzw. gesteuert wird, die Versorgung einer Sensorelektronik, auch eines im Medium liegenden Sensors, sichergestellt wird, wobei
• - die PWM-Steuerung verschiedene Frequenzkomponenten des PWM-Signals derart nutzt, dass auch ein Datenaustausch zum Rührkörper möglich ist und dass
• - eine Empfangseinheit der Gerätebasis, die von einem im Medium liegenden Rührkörper-Sensor kommenden, ebenfalls niederfrequenten Signale für eine Weiterverarbeitung aufnimmt.

In particular, by the fact that

• - Are provided structurally for an inductive transmission of energy and data in the base unit close to the footprint lying coils, and that
• - Via these coils at a relatively low frequency by means of a PWM signal, which is set or controlled by the electronic control unit in the base unit, the supply of a sensor electronics, including a sensor located in the medium, is ensured
• - The PWM control uses different frequency components of the PWM signal such that a data exchange to the stirring body is possible and that
• - A receiving unit of the device base, which receives from a lying in the medium Rührkörper sensor, also low-frequency signals for further processing.

A possibly used in the sensor unit for the sensor functionality itself or used, high-frequency signal use is generated and used only internally in the stirring body and thus remains limited to the internal sensor body, so here on the stirring body. A high-frequency signal thus does not need to be brought from outside to the sensor via an antenna connected to the sensor, nor does the base unit need to receive a high-frequency signal coming from this sensor.

Thus, and especially in a stirring body, a SAW sensor can be used without the o.g. Disadvantages can affect. But not only SAW devices use a high or even very high operating frequency directly in the sensor element or require such a high frequency. Also quite simply constructed sensors, e.g. consist only of an RC element and in which the change of the time constant represents the actual sensory elementary principle, can work more accurately or can be made smaller (small designs of a sensor) when high signal frequencies are used.

• die im Stand der Technik bekannten Antriebsformen von Magnetrührern, auch die eines reinen Magnetspulenantriebs ( ),
• die im Stand der Technik bekannte Antriebsform der „sonst üblichen Magnetrührer“
• bis die im Stand der Technik bekannte Form eines „ quadrantenerzeugenden Antriebs“ zeigen, und in einer Aufsicht und in einer räumlichen Seitenansicht,
• . und zeigen die spektralen Eigenschaften eines PWM-Signals, die für die Erfindung relevant sind. Anhand dieser bis wurden oben die Thematiken eingeordnet und bereits beschrieben; weitergehend stellen die folgenden Abbildungen dar:
• zeigt ein Blockschaltbild einer erfindungsgemäßen Anordnung
• zeigt eine an der Blockschaltung der orientierte Ausführung einer erfindungsgemäßen, SAW-Sensoren nutzenden, Sensoranordnung
• zeigt eine andere Ausgestaltung einer erfindungsgemäßen Anordnung

The invention will be illustrated below with reference to the accompanying drawings using the example of a sensor in the agitator and using a sensor that can also use a SAW sensor element will be explained. Show for that

• the known in the prior art drive forms of magnetic stirrers, even those of a pure magnetic coil drive ( )
• the known in the prior art drive form the "usual magnetic stirrer"
• to show the form of a "quadrant-generating drive" known in the prior art, and in a supervision and in a spatial side view,
• , and show the spectral characteristics of a PWM signal that are relevant to the invention. Based on this to the topics were arranged and already described above; further, the following figures show:
• shows a block diagram of an inventive arrangement
• shows one at the block circuit of oriented embodiment of a sensor arrangement according to the invention, using SAW sensors
• shows another embodiment of an inventive arrangement

shows the block diagram of an arrangement according to the invention, in which the connection between the stirring body and device base is relatively low-frequency and (as a necessary condition for a high sensor sensitivity), the sensor operates on the stirring body with a very high signal frequency. Relatively low frequency means that the transmission of energy and data between the stirring body and the device base takes place at frequencies that are significantly below the signal frequency used by the sensor system on the stirring body, which may be above 10 MHz, for example, into the upper GHz report lower frequencies does not exclude. For the transmission of energy and data between stirrer and device base, for example, signal frequencies up to 150kHz can be used, which does not preclude higher frequencies.

Above the block diagram of the are with the identifiers ( 108 ) ( 109 ) the frequency ranges; indicated with LF ( 108 ) a low-frequency connection for the supply and the data transmission from the base unit to the stirring body. In the middle, indicated with HF ( 109 ), is the high-frequency operating part of the sensor or circuit that is completely on the agitator, on the right side, again with LF ( 108 ), the second circuit part is the low-frequency operates and represents the connection from the stirring body in the direction of the device.

The primary-side (device-side) part of the circuit, which also takes over the supply of the circuit, is in total with ( 100 ) (left). On this side of the device ( 100 ), a suitable PWM signal ( 102 ) which is to have the spectral characteristics presented above by manipulating the PWM value from the device base as needed. A preparation ( 101 ) translates the PWM signal into a current that is in a coil ( 103 ), which can also be seen as an antenna, is converted into an electromagnetic field for inductive transmission. On the transmission link, not shown ( 104 ) the connection to a second coil ( 113 ) which induces a voltage from the electromagnetic field. This practically represents a transformer coupling, wherein the frequency selection (by the frequency of the PWM signal ( 102 )) is so low-frequency that the materials present in the vicinity of the transmission path can not yet have a strong damping effect. However, this frequency is much too small for sensor functions, especially for SAW sensors.

A receiving side (secondary side) existing circuit ( 111 ) generates a signal from the received signal ( 112 ) reflecting the spectral characteristics of the PWM signal transmitted from the device base. The secondary or receiver coil ( 113 ), the preparation, ( 111 ) and the signal obtained ( 112 ) already belong to the electronics of the stirring element or are available there.

The receiver coil ( 113 ) must be wrapped around the agitating body so that the windings are not guided longitudinally around the agitating body, because it is well known that that of the spool ( 113 ) wrapped around the surface perpendicular to the electromagnetic field in order to achieve efficient energy extraction from the electromagnetic field. Since this is not ensured at a coil wound longitudinally around the stirring body (which can roll freely in the medium about the longitudinal axis), a coil wound longitudinally about the stirring magnet or agitating body is not so technically particularly useful.

From the received PWM signal ( 112 ), the appropriate or required components are now obtained in the manner described. For this, the functions of the blocks ( 114 ) ( 115 ) ( 116 ), which are shown connected directly to the treatment provided.

As the most important component for the stirring element circuit as a whole, a supply voltage is used ( 117 ) from the fundamental frequency component of the PWM signal ( 102 ) ( 112 ) with the frequency f ₀ won. For this the function block ( 114 ), which may also be responsible for any communication intended for this frequency f ₀ .

The blocks ( 115 ) and ( 116 ) can represent application-dependent different functions: a first block, eg ( 115 ), the function may represent receiving data (eg ASK-modulated) on the PWM frequency f ₁ and / or (eg by load modulation) returning it to the device base (ie realizing a typical RFID application). A second block, eg ( 116 ), the function can represent, from the received PWM signal ( 112 ) to provide the frequency component f ₂ to generate from this frequency f ₂ as a reference by means of a PLL circuit, a first high-frequency signal. This can be one of the generators described below ( 118 ) ( 119 ) and / or those described below and used digital beat signals in terms of their phase position also make absolutely accessible.

The voltage ( 117 ) (here in the ) including the two clock generators ( 118 ) ( 119 ) generating a high frequency digital signal (eg 50MHz), the signal of the first generator ( 118 ) is used as a measurement signal. The actual measurement is made by transit time measurements of this signal of the first generator along several signal paths or signal branches or signal paths ( 121 ) ( 122 ) ( 123 ) realized. The signal propagation times on the signal branches relative to one another represent the actual target parameter or measured value.

From the DE10233604 the Applicant can be seen there a so-called digital beat, with the sensory tasks of the type described here can be solved by runtime measurements (and used here). By sending a first digital signal with a first frequency over several signal paths as run-time paths, some of which are used as reference paths, others as measuring paths, and - downstream of these run-time paths - digital beat signals are formed by a second generator signal, can from the relative phase of digital beat signals to each other a target parameters are determined very accurately.

In this circuit the becomes (just as an example to see) a branch ( 121 ) is used as a (first) reference path and two further (here only indicated as blocks) measuring branches ( 122 ) ( 123 ) as actual measuring sections. Each signal branch ( 121 ) ( 122 ) ( 123 ) is a D flip-flop ( 124 ) ( 125 ) ( 126 ), which, using the signal of the second generator ( 119 ) forms a digital beat; these with the D-flop flops ( 124 ) ( 125 ) ( 126 ) formed digital beat signals have a frequency which exactly the frequency difference of the two generators ( 118 ) ( 119 ) are therefore low frequency; the phase position of the digital beat signals among themselves represent the phase positions of the high-frequency measurement signal from the generator ( 118 ) after passing through the three signal paths ( 121 ) ( 122 ) ( 123 ).

This is the signal that is transmitted over the track ( 121 ) directly from the generator ( 118 ) to a first D flip-flop ( 124 ), where it arrives first in time, a general reference. In each case represents the phase position of the two high-frequency clock signals to each other.

By way of example only, it shall be assumed below that the route ( 122 ) should be used as a measuring route, the route ( 123 ) as another reference link. (The reference route ( 123 ) is intended as a reference with respect to the measuring section ( 122 ); directly over a stretch ( 121 ) without sensor element a D flip-flop ( 124 ) signal of the generator ( 118 ) reflects the phase position of the generator signals in total).

The signal (s) of the generator ( 118 ) goes through the three routes ( 121 ) ( 122 ) ( 123 ) and is delayed on these lines by a certain amount. The delay on the track ( 121 ) is low, yet present. The signal delay on the measuring section ( 122 ) is a signal delay which depends on the properties of the track, and moreover on a parameter to be measured, than the signal delay on the reference track (FIG. 121 ). The reference route ( 123 ) is used to calculate a measured value with respect to the measuring path ( 122 ) and can, for example, reflect the maximum propagation delay on the comparable route.

Of course, the number of these measuring sections (here three) can be extended by additionally inserting several measuring sections or several reference sections. The processing of the high-frequency signals on the stirring body is the same in all cases. For each measuring section, a D flip-flop ( 124 ) ( 125 ) ( 126 ) intended.

In the following diagrams, the symbol of a multiplier is used for these D flip-flops, but this is to be understood as equivalent. A multiplier (eg a Gilbert cell) can process analog and digital signals, a D flip flop requires digital signals. Here it is only important that at the outputs of the D-flip-flops (or multiplier), a low-frequency signal is generated in each of which the phase angles of the signals of the two generators ( 118 ) ( 119 ) (from the first generator ( 118 ) after passing the delay lines). These low-frequency beat signals are transmitted over the track ( 105 ) to a unit on the equipment side, represented by the block ( 106 ). The signal received there ( 107 ) is available to the device for evaluation.

In this presentation of the is behind every D flip flop ( 124 ) 125 ) 126 ) one component each ( 127 ) ( 128 ) ( 129 ) which is to transmit the respective digital beat signal to the device base. As will be shown later, this can often be done with a single signal; Here, the transmission is shown separately to simplify the functional representation.

shows one at the block circuit of oriented embodiment according to the invention:

The transmission from the device to the sensor or stirring element ( 180 ) is low frequency. The Components for this transmission or the functional area intended for this purpose are with LF ( 204 ).

From a base-site generator ( 173 ) is a PWM signal with a defined frequency or period ( 170 ) and a variable pulse duration ( 171 ), prepared ( 174 ), eg reinforced, and a primary-side transformer coil ( 176 ). The illustrated GND reference ( 175 ) is assigned to the base unit. This side of the device (as in the block diagram also on the left side) is indicated by the boundary and arrows ( 172 shown); comparable to the sensor side through the illustrated boundary and arrows ( 178 ).

The coupling ( 177 ) between the base unit and the sensor takes place inductively via the transmission path ( 177 ) (in which inter alia the material of the mounting plate, the glass of the Aufstellgefäßes, parts of the medium, etc. are) by means of coils (inductors). The inductive-transformer coupling ( 177 ) by means of coils primary ( 176 ) and secondary ( 179 ) at such a low frequency (eg 62.5kHz) that by the in the range of the transmission line ( 177 ) materials can not restrict substantial transmission loss. The given energy and data transport from the base unit to the sensor is indicated by arrow ( 178 ).

Sensor side ( 178 ) creates a component ( 181 ) from the one with the coil ( 179 ) received PWM signal a voltage for supply ( 183 ) of the sensor circuit, which can be done simply by rectification and screening of the received signal, for example. This same component ( 181 ) can extract data in the form of phase jumps at the fundamental frequency f o, which may be due to PWM signal manipulations that may have been deliberately performed by the base unit. From this data channel, for example, broadcasts can be received by the base unit and provided to the sensor without disturbing the energy transport at the fundamental frequency.

A second sensor-side component ( 182 ) obtains from the received PWM signal from the first harmonic at the frequency f ₁ and the phase position φ ₁ data of a second data channel over which the device wants to communicate. From this signal but also, for example by means of a PLL generator, a first high-frequency signal can be generated, so that one of the generators required here ( 184 ) 185 ) could possibly be omitted. The supply ( 183 ) is used to connect the two generators ( 184 ) and ( 185 ) and also to operate the rest of the sensor circuit.

• - mit einer direkten Zuleitung eine erste Referenzstrecke (Refl) und erreicht eine erste Mischstufe (196),
• - auf einem zweiten Signalweg wird das Signal dieses ersten Generators (184) in einem ersten SAW-Sensor (187) mit einem Interdigitalwandler (190) (IDW) in eine akustische Oberflächenwelle umgewandelt, die auf der Oberfläche des SAW-Sensors (187) eine geometrisch definierte Strecke (187) durchläuft und am Ende der Strecke (187) mit einem IDW (192) wieder zurück in ein digitales Signal gewandelt wird. Dieses digitale Signal erreicht so, laufzeitbedingt verzögert, eine zweite Mischstufe (195),
• - auf einem dritten Signalweg, der dem zweiten Signalweg vollständig gleichen kann, wird das Signal des ersten Generators (184) in einem zweiten SAW-Sensor (188), wieder mittels IDW (191), in ein akustisches Oberflächenwellensignal und nach dem Durchlauf der Strecke des SAW-Sensors (188) mittels IDW (193) wieder zurück in ein digitales Signal gewandelt, das ein dritte Mischstufe (200), laufzeitbedingt verzögert erreicht.

The signal of a first generator ( 184 ) (which has an area of 2x2mm and a supply current of less than 1mA to generate a digital clock signal with a frequency of 50MHz, for example) is used here for a transit time measurement on three routes: As for the block diagram of represented, passes through this signal ( 186 )

• - With a direct supply line, a first reference path (Refl) and reaches a first mixing stage ( 196 )
• on a second signal path, the signal of this first generator ( 184 ) in a first SAW sensor ( 187 ) with an interdigital transducer ( 190 ) (IDW) is transformed into a surface acoustic wave which is emitted on the surface of the SAW sensor ( 187 ) a geometrically defined path ( 187 ) and at the end of the route ( 187 ) with an IDW ( 192 ) is converted back into a digital signal. This digital signal reaches a second mixing stage (delayed due to the delay) ( 195 )
• on a third signal path, which can completely equal the second signal path, the signal of the first generator ( 184 ) in a second SAW sensor ( 188 ), again using IDW ( 191 ), into a surface acoustic wave signal and after passing through the path of the SAW sensor ( 188 ) by means of IDW ( 193 ) is converted back into a digital signal, which is a third mixing stage ( 200 ), delayed due to runtime.

Depending on the conditions for the respective SAW sensor, the transit times that occur are influenced by all essential parameters; This includes, among other things, the temperature. The two SAW sensors ( 187 ) ( 188 ) generate from the clock signal of the first generator ( 184 ), two signals delay-delayed relative to one another, which in themselves show the same run-time behavior if all the influencing parameters are equal. If the sensor used as a reference is separated from the measuring parameter, eg by insulation, then all other parameters are still effective during the runtime of this reference sensor, but not the target parameter. The difference in the transit times of the measuring sensor and the reference sensor is thus determined iW only the actual target parameter; Runtime changes caused by other parameters are the same for both SAW sensors. (In this regard, the assignment of the SAW sensors to a reference and / or a measurement branch is therefore interchangeable)

• - Da das erste niederfrequente digitale Schwebungssignal (197) aus den beiden Generatorsignalen direkt gebildet wird (die Laufstrecke ist mit Refl bezeichnet und besteht nur aus einer direkten Verbindungsleitung), ist diese Laufzeit minimal und spiegelt damit nur die relativen Phasenlagen der beiden Generatoren wieder.
• - Die Phasenlage des zweiten niederfrequenten digitalen Schwebungssignals, das der Mischer (195) erzeugt, spiegelt eine erste SAW-Sensor-Laufzeit vom ersten SAW-Sensor (187) wieder, die hier z.B. als Referenz (Ref2) genutzt wird, weil ein (Ziel-) Parameter (z.B. durch Isolation) diesen Sensor nicht beeinflusst, aber z.B. dem Temperatureinfluss in der Laufzeit genauso folgt, wie der zweite SAW-Sensor (188).
• - In der Phasenlage des dritten niederfrequenten digitalen Schwebungssignals (das der Mischer (200) erzeugt) spiegelt sich die Laufzeit des zweiten SAW-Sensors (188) wieder, der allerdings vom eigentlichen Zielparameter nicht isoliert worden ist und daher in seiner Laufzeitverzögerung diesen Parameter mit repräsentiert.

The mixing stages (three multipliers ( 195 ) ( 196 ) ( 200 )) at the ends of the signal lines form from the delay-conditioned delayed digital signals and using the signal of the second clock generator ( 185 ) three low-frequency digital beat signals from:

• - Since the first low-frequency digital beat signal ( 197 ) is formed directly from the two generator signals (the path is designated Refl and consists only of a direct connection line), this run time is minimal and thus reflects only the relative phase angles of the two generators again.
• The phase of the second low-frequency digital beat signal that the mixer ( 195 ), a first SAW sensor transit time from the first SAW sensor ( 187 ), which is used here as reference (Ref2), because a (target) parameter (eg due to isolation) does not influence this sensor, but, for example, follows the temperature influence in the runtime just as the second SAW sensor ( 188 ).
• In the phase relationship of the third low-frequency digital beat signal (which the mixer ( 200 ), the transit time of the second SAW sensor ( 188 ), which, however, has not been isolated from the actual target parameter and therefore represents this parameter in its propagation delay.

The low-frequency beat signals reflect in their phase positions the transit times of the high-frequency signals relative to each other; The actual target parameter is represented in the runtime difference.

The low-frequency beat signals are (here only by way of example) with light emitting diodes (eg ( 198 ) ( 199 )) to the device side. These signals could also be transmitted to the device side again by a transformer coupling, but one might have the problem that with the inductive coupling on the left side ( 177 ) could come into conflict. This is not a fundamental problem, but is avoided here for ease of illustration. On the receiving side of the device is only a simple receiving diode ( 201 ), which in the usual way with a series resistor ( 202 ), which provides the signal to be transmitted.

As an example of a possible single-channel signal transmission, Fig. 8 'shows the digital beat signals in a pulse diagram: the beating signal used as a reference, which is transmitted by the mixer ( 196 ), turns on or off a single LED as a whole by pulling the series resistor of the LED to GND. Those of the mixing stages ( 196 ) ( 200 ) in which the propagation times of the signals passing through the SAW components relative to this reference are represented by an XOR gate ( 209 ) connected. At the output of the XOR gate lies with the pulse ( 208 ), in the duration of which the transit time difference on the two SAW sensors, based on an RF period, represents a measured value for the target parameter, but is now transformed to the (small) difference frequency of the clock generators used. For the duration of this pulse ( 208 ), the single LED turns on, which coincides with the beating signal period ( 207 ) the difference frequency repeated.

At a clock signal frequency of, for example, 50 MHz (and, for example, a difference frequency of, for example, 1 kHz), that of the clock generators ( 184 ) ( 185 ), digital beat signals are generated at 1kHz (1ms period). The achievable temporal resolution for the transit time determination is thus theoretically at 0.4ps (based on the RF clock period of 20ns), ie in the digital beat signal with a period of 1ms at about 2ns, which is not transmitted because of the band limitation of the transmission link can be. Resolution-limiting are thus only the properties of the transmission path itself, but this is generally above a resolution achievable with the usual ADCs.

So it is also possible to use a SAW sensor in a stirring body of a magnetic stirrer in order to use it, for. capture and display molecular processes or chemical, biological, physical parameters in the respective medium.

A finding in the patent literature direct coupling of the IDWs of a SAW sensor, which is to be in the medium, by a longitudinally wound around the agitator wire as an antenna (a coil that will not let high frequencies through) and directly with the SAW Sensor should not be able to work.

Only with the use of the technique according to the invention is the use of SAW sensors achieved with their great potential applications. It should be noted at this point that the inventive technique has a seemingly complicated background, but in general can be realized without much effort. For a magnetic stirrer with a drive according to Fig.1a or In addition, the effort is small or the mechanical structure easy to do, in a magnetic stirrer with a drive according to At least the mechanical structure is a bit more difficult but not impossible to solve.

shows a further embodiment of the invention or circuit in which also SAW sensors, but also very elementary RC sensors can be used; top again with the delimitation (LF) of the low-frequency operating areas for transmission of energy and data between base unit and stirrer and by (HF) delimited, the high-frequency side working area for use of the SAW sensors in the stirring body.

The base unit side primary circuit part, in total with ( 151 ) consists of a generator for generating a PWM signal ( 150 ), a (amplifier) adaptation and the primary-side coil of a connection conceived as a transformer. The two coils from the So here are understood as the primary-side and secondary-side winding of a transformer. The transmission takes place, as already for represented over an unspecified route ( 152 ) Wirelessly between a device-side, designed as a coil transmitting antenna to a rührkörperseitig designed as a coil receiving antenna.

On the device side, a PWM signal ( 150 ), with properties that have been presented above as bases. Removed from the secondary transformer coil, the two components ( 153 ) ( 154 ) in the already described manner from the frequency component f ₀ ( 153 ) both the provision of the power supply, as well as a data transmission phase demodulation.

The use of the second frequency component ( 154 ) with the frequency f ₁ and the phase position φ ₁ through the component ( 154 ) can provide a second data channel.

Like already to two high-frequency generators ( 155 ) and ( 156 ) used as clock generators to realize the functionality already described by running time measurements. The signal of a first generator ( 155 ) is sent here over four measuring distances.

• - eine erste Referenzstrecke (157) (Refl), in der sich nur die Phasenlagen der beiden Generatorsignale repräsentieren,
• - eine zweite Referenzstrecke (158) (Ref2), bei der das Signal über eine erste SAW-Sensorstrecke läuft und
• - zwei weitere völlig gleich ausgestaltete Signalstrecken mit SAW-Komponenten (159), (160).

These four routes are used as

• a first reference link ( 157 ) (Refl), in which only the phase positions of the two generator signals represent,
• a second reference link ( 158 ) (Ref2), where the signal passes through a first SAW sensor link and
• - two further signal lines with identical components and SAW components ( 159 ) 160 ).

The respective SAW sensor causes in the real sense a time and space defined signal transit time (as acoustic surface waves from the one end of the sensor to the other end of the sensor) so both terms, ie sensor and signal path are practically regarded as synonyms.

The SAW sensors ( 158 ) ( 159 ) ( 160 ) are in the and recognizable by the fact that each interdigital transducer are shown on the left and right, at the inputs and at the outputs. The actual design of these SAW sensors as components may look different; important here in the context is only their function, signals from the one generator ( 155 ), depending on acting parameters, different delay. The assignment of the meaning of the term as a reference or as a measured variable is application-dependent and will vary from case to case.

However, the concept described here only by way of example using SAW sensors is not limited to SAW sensors. The use of SAW sensors is known in the art, as stated above. In bottom left is the representation of such a SAW sensor shown again, in total with ( 163 ) designated.

Any construct whose elements (however, whatever) cause a time delay can be used in this inventive sensor concept based on variable propagation time characteristics of signal paths. This can be achieved with the simplest RLC sensor systems (sensors that use variable resistances (R) and / or capacitances (C) and / or inductances (L) depending on a physical parameter). For example, RC elements can also be used according to the invention. In bottom left is the representation of such an RC-based sensor, in total with ( 164 shown in this form instead of the illustrated SAW sensors ( 158 ) ( 159 ) ( 160 ) can be used with comparable functionality. The description of the function would be the same as for the SAW based sensors.

In general, a SAW element provided for a measurement will be accessible to the respective target parameter, while a reference path will be isolated or at least rendered insensitive to this parameter.

If e.g. the surface of a SAW sensor substrate is occupied by a marker to which a specific molecule can bind, which makes the SAW sensor sensitive to specific molecule binding, then that surface must face that molecule in the liquid and be accessible. However, this molecule-specific SAW sensor is also affected by other parameters, e.g. from the temperature, influenced. If a specific effect is observed with such a highly specific SAW sensor, it can not be stated with certainty how much of a change in the measured value that has just been recorded is merely due to a temperature change.

If a reference path with a precisely identically constructed SAW sensor is now used, this SAW sensor is however - for example -. by a coating - isolated with respect to the liquid or the molecules, this sensor will show a - at least with respect to the temperature - the same behavior; However, an effect coming from binding molecules will be missing, an effect added by the coating may additionally be noticeable. It may therefore happen that different parameters have different effects, which can only be eliminated with further references.

As another example, a first reference ( 158 ) an upper and a second reference ( 160 ) represent a lower measurement value, eg by placing the markers on the SAW surface of the first reference sensor ( 158 ) completely filled with molecules and then sealed the surface, and the markers on the SAW surface of the second reference sensor ( 160 ) without any molecular occupation also sealed. It is thus possible to distinguish between a fully occupied SAW sensor and a completely empty SAW sensor as a reference (but different due to sealing) and each measurement on a third SAW sensor ( 159 ) in the context of the minimum and the maximum.

As another example, a temperature measurement with an RC element (at ( 159 )) are carried out with a temperature-dependent resistance by using further RC elements without temperature-dependent resistors as a reference, a first reference ( 158 ) an upper and a second reference ( 160 ) represent a lower possible measurement value, eg by using a first reference RC element with a maximum possible resistance independent of the temperature, as a first reference and an RC element with a minimum possible resistance independent of the temperature as a second reference ,

The composition of the signal delays allows to establish both a reference to the signals, to the references, and also to the measured quantities in a single measuring step.

The formation of digital beat signals, in achieved by D flip-flops, is here again by (multiplying) mixing functions ( 161 ). The mixers ( 161 ) form digital beat signals, which may be on the order of a few kHz or even a few hertz, but only by the difference frequency of the two clock generators ( 155 ) and ( 156 ) or derived from these clock frequencies is determined. The transmission of the digital beat signals from the stirring body to the device base and the evaluation of the transit times takes place as already described.

The transmission of signals in a magnetic stirrer is not optical ( 162 ) (although that is of course possible). The four signals that are to be transmitted here can, however, be converted into a single signal relatively easily (Fig.9 '), so that the in indicated receiver circuit of a series resistor ( 166 ) and a photodiode with a device-side GND reference ( 165 ) with the signal ( 167 ) provides all needed information. The reference values (signal 2 and 4 ) are linked (as an example) to an XOR gate. The output signal (signal 5 ) of this XOR function is linked to a low-frequency, non-50% duty-cycle signal by means of the AND function, as a result of which this non-50% duty cycle is only reached during the period in which the two reference signals also move in the runtime. Cycle signal is forwarded. With the actual measuring signal (signal 3 ) is linked by means of a second XOR function, the non-50% duty-cycle signal is from the measured value signal (signal 3 ), once inverted, once not inverted, and so (signal 6 ) be transmitted.

With the period of the signal thus transmitted, the frequency difference of the signals generated by the clock generators is known; the duration of the transmitted non-50% duty cycle signal represents the measurement range (e.g., 0-100 degrees); the inversion of the non-50% duty-cycle signal caused by the measuring signal indicates exactly where the measured value lies in the measuring range. A suitable evaluation is thus accessible to the person skilled in the art by the illustrations of the PWM properties.

Claims (10)

Magnetic stirrer with a stirrer drive and with at least one stirring element (2) inserted or insertable into a vessel (28) with a medium to be stirred and containing a magnet for driving coupling to the stirrer drive and means for transmitting data and / or energy (103 ) (104) (113) for a supply of sensors and an electronic circuit (178) (110) (120) in the stirring body, which requires or be used for the sensor functionality in the agitator high-frequency signals, characterized in that the stirring body two clock generators (184) (118) (185) (119) for generating at least two high-frequency digital clock signals having a small frequency difference and from these clock signals digital beat signals (197) (124) (125) (126) are formed. Magnetic stirrer according to Claim 1 , characterized in that at least two digital beat signals (125) (126) are obtained in that one of the two high-frequency clock signals (121) over at least two Signal paths (122) (123) is passed, resulting in at least two delay-delayed delayed clock signals, and the digital beat signals are formed from the clock signals after the passage of the signal paths (125) (126). Magnetic stirrer according to Claim 2 , characterized in that in the at least two signal paths (122) (123) are elements and / or components that significantly determine the transit time for a clock signal (121) that runs over these signal paths (122) (123). Magnetic stirrer according to Claim 3 , characterized in that run times on a signal path (187) (188) by elements connected in the signal path and / or components that use a signal transport by vibrations and / or waves, in particular mechanical-acoustic effects, in particular by SAW sensor elements, be significantly influenced. Magnetic stirrer after at least one of Claims 1 to 4 characterized in that the digital beat signals (197) (199) are each derived from one of the at least two clock delayed clock signals derived from the signal (186) of the first clock generator (184) and the clock signal (194) selected from second clock generator (185) is derived, by means of D flip-flop (124) (125) (126) or a multiplicative mixing stage (196) (195) (200) are formed. Magnetic stirrer after at least one of Claims 2 to 5 , characterized in that of the signal propagation times, which result from the signal transport on the at least two signal paths (157) (158) (159) (160), the transit time of at least one signal path (157) (158) as a reference for the duration of at least one other signal path (159) (160) is used. Magnetic stirrer after at least one of Claims 1 to 6 , characterized in that provided for supplying the sensors and an electronic circuit in the stirring body data and / or energy generated by the device base PWM signals with selectively manipulated PWM ratio and transmitted inductively. Magnetic stirrer after at least one of Claims 1 to 7 , characterized in that for supplying the sensors and an electronic circuit in the stirring body data and / or energy to such low frequencies are transmitted inductively (152) that the materials commonly present in the environment of the stirring body, the transmission is not significantly attenuate or disturb. Magnetic stirrer after at least one of Claims 1 to 8th , characterized in that the coils required for the inductive transmission of data and / or energy (152) on the secondary side in the stirring body are not wrapped lengthwise around the round, rod-shaped stirring magnet, but surround the stirring magnet as round coil core or are wound around it, in order to prevent the mixing of the transmission from being interrupted by the agitator which may be rolling freely in the medium. Magnetic stirrer after at least one of Claims 1 to 9 , characterized in that the measuring principle for sensory detection of a parameter by the agitator based on a transit time difference measurement, all beat signal frequencies of the frequency difference of the clock signals derived from the two clock generators, and a measured value from the time difference of the clock edges in the beat signals, in particular formed by subtraction or is derived.

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