Device and method for operating a Coriolis mass flow meter

The invention relates to an apparatus and a method for operating a Coriolis mass flow meter, according to the preamble of claim 1.

One known method is that the flowmeter two sensors for Detection of measuring tube movement and an actuator for the mechanical excitation of the measuring tube has. Furthermore, there is a sensor for the temperature measurement and the measuring tube sometimes a sensor for the case temperature measurement.

In W098 / 52000 discloses a method and a device for detection and compensation described by zero influences on mass flow meter, in which there are three sensors for detecting the movement of the measuring tube and an actuator for the mechanical excitation of the measuring tube.

In the known arrangements, the sensor coils for detecting the measuring tube movement are and the actuator coil to generate the power for the measuring tube vibration used. rising costs and error rates in the device with the number of actuators and sensors used.

The object of the invention is to provide a simplified device and a simplified to provide methods for a mass flow meter. The object is solved by the apparatus with respect to the characterizing Features of claim 1 and the characterizing respect to the method by Features of claim 9. So according to the invention are connected to the measuring tube at least two active modules attached, each as an exciter (actuator) and / or as a measured signal receiver (Sensor) are operable. In a particularly advantageous embodiment, the active components are as plunger donors formed, each having a coil and a magnetic core movable therein. Such a plunger-giver known to work so that the Sensor operation, a displacement of the magnetic core, a voltage induced in the coil, whereas in the actuator operation applying an alternating voltage to the Coil magnetic core periodically excites oscillations.

In the inventive arrangement, each coil can be either as a sensor for Gathering the Messrohbewegung or as an actuator for generating the force for the find measuring tube vibration use. This makes it possible to operate the measuring tube in different oscillation modes. Further, the coil by utilizing the phase information between find the voltage and current simultaneously as actuator and sensor use.

Furthermore, there is redundancy, so that the meter even after Failure of a sensor / actuator works. The operator may have a warning be informed of the current emergency, and thus has the possibility prepare for the replacement or repair.

By way current and voltage of each sensor / actuator to measure, is it is possible to determine the resistance of the coil. Thus, a wire break detection or temperature measurement possible. (The copper resistance changes depending on the temperature)

Since the analog-digital converter are synchronized, is a measurement of the time shift between current and voltage, the actuator, but also between the actuator and sensor possible.

In a particularly important and simple arrangement, each individual coil be used simultaneously as an actuator and sensor. For this purpose, both the amplitude and the phase of the respective coil current measured. From the phase relationship and the amplitude ratio between the applied actuator voltage and the coil current can be induced by the measuring tube movement Calculate voltage. This results in particular the phase of the measuring tube vibration.

The described simultaneous use of the coil as an actuator and sensor can the flowmeter also work with only two coils.

A first realization could be in the previous devices (prior art) simply omit the actuators. Possibly but other arrangements are also conceivable. The position of now only two coils may for example both the optimized sensor function as well as on the actuator function back. (Sensors should be as far as possible away from the center of the unit to a large to include phase shift. In contrast, transfer the actuators her strength optimally when they are grown as close to the center.)

Possibly there are on the unit positions with maximum possible emf, thus the maximum possible Deflection, which are not in the middle of the unit. Furthermore, it should be noted that this arrangement special requirements the coil and magnet shapes provides. Thus, in the prior art in the devices ia drive us sensor linear motors of different designs.

In Figur1 a possible embodiment of the invention is shown.

A, C, B are the sensor coils, but which can be used as an actuator as well.

. The other components shown in Figure 1 are:<dl tsize="17" compact="compact"><dt><b>DSP / CPU:</b></dt><dd>Digital Signal Processor / Central Processing Unit (Microprocessor)</dd><dt><b>ADC:</b></dt><dd>Analog-Digital-Converter</dd><dt><b>DCA:</b></dt><dd>Digital-Analog-Converter</dd><dt><b>TP:</b></dt><dd>Low Pass Filter</dd><dt><b>SA, SB, SC:</b></dt><dd>Switch for sensor / actuator A, B, C</dd><dt><b>TP1, TP2, Th:</b></dt><dd>Temperature sensors for detecting the pipe temperature (TP1, TP2) or the ambient temperature (Th)</dd><dt><b>VA, VA ', VB, VB',VC, VC ':</b></dt><dd>amplifier</dd><dt><b>SA, SB, SC:</b></dt><dd>Sensor signal from sensor / actuator unit A, B, C</dd><dt><b>UA, UB, UC:</b></dt><dd>Drive voltage for sensor / actuator unit A, B, C</dd><dt><b>IA, IB, IC:</b></dt><dd>Flow meter of sensor / actuator unit A, B; C</dd></dl>

About the controlled by the DSP switches SA, SB and SC, switchover between the operating modes as a sensor or actuator for each sensor coil A, B or C.

<u>Sensor operation:</u> In operation as a sensor, the induced voltage sensor using amplifies an input amplifier, band limited (anti-aliasing filter) followed by an ADC supplied. In the example of FIG. 1, for example the A sensor signal of the coil to the amplifier VA supplied via the switch SA, there reinforces, the low pass filter TP and after this is supplied to the analog-to-digital converter ADC, after which the pre-processed in such a way sensor signal SA then the DSP in digital signal processor is supplied for further processing. carried analog the signal processing in the respective paths for the coils C and B.

In operation, as a sensor, the switches SA, SB and SC are not shown in Fig. 1 Shift position, but in accordance with in the other switching position.

actuator operation:

If the sensor coils A, B, C are operated as an actuator, so the switches SA, SB and SC brought into the switching position shown in FIG. 1, controlled by a signal from the digital signal processor DSP, as indicated by the corresponding Point bonds. Of the digital signal processor, the respective output target value for the coil voltage UA, UB, UC and via a digital to analog converter DAC generates a sine signal with the aid of a downstream low-pass filter TP band-limited and then a corresponding associated power amplifier VA ', VB', VC 'to the respective actuator coil A, B or C is applied.

Simultaneously, the actuator current from the amplifiers VA ', VB' is, VC 'back recorded a low-pass TP band limited initially and thereafter through an analog-digital converter ADC digitizes and as current measurement value IA, IB or IC digital Signal processor supplied for further evaluation.

The analog-to-digital converter are synchronized thereby, so that at any time the information on the phase relationships between each Actuator current IA, IB and IC and the respective actuator voltage UA, UB or UC is known.

Furthermore, at least one measurement of the measuring tube temperature (Tp1, Tp2) and a further measurement of body temperature (Th) done. The measured values the aforementioned temperature sensors are shown top right in FIG. 1, also via respective pre-amplifier, low-pass filters and analog-to-digital converter as temperature signals to the digital signal processor for further processing supplied.

The stored in the digital signal processor program then determines which of the three coils A, B, C as an actuator and which are operated as sensor. So can For example, the coil C to be operated as an actuator, the switch SC would be in indicated in Fig. 1 position. The other two coils A, B could then are operated as sensor coils, then the corresponding switches SA would and SB in the other switching position.

It could also consist a useful operating state in which coil A as to operate the actuator and the coils C and B as a sensor. Then, the switch SA would would be in its in FIG. 1 switch position shown, and the switches SB and SC in each case in the other switching position.

Overall, however, in the embodiment of Fig. 1, each coil only in a previously selected operating mode, either as an actor or as a sensor operable.

In FIG. 2, a further possible embodiment of the inventions is illustrated. In the Embodiment of FIG. 2, the assignment of the relevant mode of operation for one of the Coils, namely whether it is operated as a sensor or as an actuator, a much more flexible is handled as in the embodiment according to Fig. 1. Another difference that in the embodiment of FIG. 2, four coils, namely A, B, C, D are attached to the measuring tube. The temperature sensors Tp1 and Tp2 for detecting the pipe temperature at the tube inlet and the tube outlet and the temperature sensor Th for detecting the body temperature are also in the execution provided back to FIG. 2. In contrast to FIG. 1, however, the signal detection path - Amplifier, low-pass TP, analog-to-digital converter ADC - for detecting the temperature signals present only once, see Fig. 2, upper right. A multiplexer ensures that, controlled by the digital signal processor DSP via a corresponding line of action between the digital signal processor, and this multiplexer, each in turn the temperature signals of the three temperature sensors Tp1, Tp2, Th can be queried. This embodiment saves up some components, since the temperature sensor signal acquisition path to be carried out easily needs.

Is by, in contrast to the embodiment in the embodiment of FIG. 2 Fig. 1 with the assignment shown there, the operating mode of a relatively firm Coil, the assignment of the operation modes of the individual coils implemented using multiplexers. The Aktoransteuerungstreiber which of the voltage paths - Voltage signal U, digital-to-analog converter DAC, low-pass TP, amplifier - and appropriate returns the current signal - via a further low-pass TP, analog-to-digital conversion of an analog-to-digital converter ADC to the current signal I - made correspond to those described with Fig 1 already.. In the embodiment of FIG. 2, two such driver circuits for the actuator control provided, once described with UA or IA and IB or UB. About each one the amplifier associated multiplexers can now Aktoransteuerungsspannung each of the four coils A, B, C, D are assigned. Which of the respective coils the Aktoransteuerungsspannung is allocated, decides due to the provided program in the digital signal processor DSP. The selection and Driving the multiplexer takes a Multiplexersteuerleitung. To this Way is a very flexible selection of the operating mode for each of the four coils possible.

Below the Aktoransteuerungstreiber are shown in FIG. 2, three signal paths for detecting shown the sensor voltage of a coil. The signal paths are made as already described above in FIG. 1, an amplifier, a low pass and an analog-to-digital converter ADC. Between the amplifier and the respective Coil is also here in the embodiment of FIG. 2 are each a one multiplexer assigned signal path. The signal path multiplexers are the Multiplexersteuerleitung controlled and selected. In this way, it is possible to very flexibly intrude each of the four coils on each of the three signal paths, depending on as is the case under stored in the digital signal processor program. The operation the device is characterized overall very flexible to handle.

Another advantage of the embodiment of FIG. 2 is that it is now is possible to operate a spool simultaneously both as an actuator and as a sensor. This is due in consideration of the specification set forth above.

Namely, for example via the Aktoransteuerungspfad UA / IA coil A are driven as an actuator and at the same time via the signal path C, the coil signal are recognized as a sensor signal when the two multiplexers involved accordingly are connected.

could a possible sensible sequence of activation of the four coils A, B, C, D for example, be such that the coil A and B are operated as actuator coils, the coil C and D as sensor coils, and shortly thereafter the coils C and D as Actuator coils, and the coils A and B as sensor coils.

Displayed 1 and 2 in the embodiments of FIGS electronic Components, such as amplifiers, multiplexers, low-pass filters, analog-to-digital converter, Digital-to-analog converters are well known in the rest of electronic assemblies and depending on the state of the art with modern devices prepared, but the skilled man are available so far. The same applies to the illustrated digital signal processor DSP.