In a Coriolis mass flow meter for determining the concentration
of a flowing fluid, a concentration function is stored in a concentration
evaluating unit. This enables the user to produce a concentration
value at given temperature and density of the medium appropriate
for a given application.
4. A coriolis mass flow meter for determining the concentration
of a flowing fluid, comprising: a digital signal processor (DSP),
which determines from the sensor signals and the temperature signals
of the transducer the density of the flowing fluid; and a concentration
evaluating unit connected thereafter, in which a concentration curve
5. The coriolis mass flow meter as claimed in claim 4 wherein:
the concentration curve is stored in the form of a two-dimensional
6. The coriolis mass flow meter as claimed in claim 5 wherein:
the degree of the density polynomial is 4 and the degree of the
temperature polynomial is 3.
 The invention relates to a Coriolis mass flow meter for
 Coriolis mass flow meters are used in many cases for determining
mass flow of a fluid in a section of a pipeline. In this, the fluid
flows through at least one oscillating measuring tube. In most Coriolis
mass flow meters, one oscillation exciter and two oscillation sensors
are arranged on the measuring tube. Measuring tube and fluid form,
together, an oscillatable system, which is normally excited to its
resonance frequency. The resonance frequency depends on, among other
things, the material and the dimensions of the measuring tube. It
varies, additionally, with the density of the flowing fluid. In
some cases, the measuring tube is not excited to the resonance frequency,
but, instead, to a neighboring frequency. The two oscillation sensors
register the oscillatory motion of the measuring tube at two locations
spaced from one another in the direction of flow and convert the
oscillatory movements of the measuring tube to sensor signals. Both
sensor signals have the same frequency as the oscillatory movement
of the measuring tube, but they are shifted in phase relative to
one another. The phase shift between these two sensor signals is
a measure of the mass flow rate.
 The sensor signals are evaluated in a signal processing
unit and converted into a signal proportional to the mass flow rate.
Besides the mass flow rate, other properties of the fluid can also
be determined, for example its density. For this purpose, the frequency
of the oscillatory motion of the measuring tube is evaluated and,
if need be, the temperature of the flowing fluid is determined.
 Such a Coriolis mass flow meter is known from the commonly-owned
patent application DE 100 45 537.
 Often in industrial processes, the concentration of a solution
is a measured quantity of interest. This is true for mass- and volume-concentrations,
as well as for various industry-specific concentration specifications,
such as .degree.Oechsle in wine-production or .degree.Plato in beer
brewing. A basic ingredient for the measurement of concentration
in most cases is the density of the fluid. Correspondingly, various
density functions, for example .degree.Brix, .degree.Plato, .degree.Balling,
.degree.API, are already implemented in the Coriolis mass flow meters
Promass 63 and Promass 83 of the firm Endress+Hauser.RTM.).
 Various concentration measures are, however, not defined
unequivocally in the literature. Different users apply different
definitions, which then lead to different concentration values.
 In the case of conventional Coriolis mass flow meters, the
output of different concentration values is only conditionally possible.
 It is an object of the invention to provide a Coriolis mass
flow meter for concentration measurement, which is simple and economical
 This object is achieved by a Coriolis mass flow meter for
concentration measurement as defined in claim 1.
 Advantageous further developments of the invention are given
in the dependent claims.
 An essential idea of the invention is the providing in the
Coriolis mass flow meter for measuring concentration a unit, in
which a predeterminable concentration curve is stored.
 There follows a more detailed explanation of the invention
on the basis of an example of an embodiment, as illustrated in the
drawings, which show as follows:
 FIG. 1 a schematic drawing of the transducer of a Coriolis
mass flow meter; and
 FIG. 2 a block diagram of a signal processing unit for a
Coriolis mass flow meter having a concentration determining unit.
 FIG. 1 is a schematic drawing of a transducer 1 for a Coriolis
mass flow meter. The transducer 1 is arranged in a pipeline, which
is not shown in further detail. A fluid F flows in the pipeline.
The mass flow rate of the fluid is one of the parameters of interest.
The connection with the pipeline is by way of the two flanges 2
 The transducer 1 includes a single, straight measuring tube
4 which is secured at its inlet end at the flange 2 by an end-plate
13 and at its outlet end at flange 3 by an end-plate 14.
 The flanges 2 3 and the end-plates are secured on or in
a support tube 15.
 For causing the measuring tube to oscillate, an oscillation
exciter 16 is arranged at the middle of the measuring tube 4 between
the two end-plates 13 14. The oscillation exciter 16 can be, for
example, an electromagnetic drive composed of a permanent magnet
161 and a coil 162. The coil 162 is secured to the tube 15 and the
permanent magnet to the measuring tube 4. The amplitude and the
frequency of the bending oscillation of the measuring tube 4 which
occurs in the plane of the drawing, are controlled by the electrical
current flowing in the coil 162.
 Coriolis forces arise in the plane of the drawing, when
a fluid F flows through the measuring tube 4. A result of these
forces is that all points of the measuring tube 4 no longer oscillate
 The oscillatory motion of the measuring tube 4 is registered
with the help of two oscillation sensors 17 18 which are arranged
likewise on the support tube, about symmetrically on either side
of the oscillation exciter 16. The oscillation sensors 17 18 can
be, for example, electromagnetic converters, which are constructed
similarly to the oscillation exciter 16.
 The two permanent magnets 171 181 thereof are secured to
the measuring tube 4 and the two coils 172 182 are secured to the
support tube 15. The motion of the measuring tube 4 causes the magnets
171 181 to induce voltages in the associated coils 171 181 and
these voltages are tapped as analog sensor signals X.sub.17 respectively
 Two temperature sensors 20 19 serve for registering the
temperature of the fluid.
 Temperature sensor 19 is located on end-plate 13 and temperature
sensor 20 is on support tube 15.
 Transducer 1 is connected to a digital signal processing
unit DSP. The signal processing unit DSP delivers at its outputs
the measurements mass flow rate, density and temperature of the
flowing fluid F.
 FIG. 2 is a block diagram of the signal processing unit
associated with the transducer 1. Among other things, it evaluates
the sensor signals X.sub.17 X.sub.18 and it regulates the oscillation
excitations of the measuring tube 4. The two sensor signals X.sub.17
and X.sub.18 are fed, respectively, to a first amplifier V.sub.1
and a second amplifier V.sub.2. The amplification of the amplifier
V.sub.2 is variable via an adjustable amplification factor.
 The amplifier V.sub.1 is connected to an A/D converter AW.sub.1
and to a difference stage D, in parallel therewith. The amplifier
V.sub.2 is connected to a second input of the difference stage D.sub.1.
The output of the difference stage D.sub.1 is connected to a second
A/D converter AW.sub.2. The two outputs of the A/D converters AW.sub.1
and AW.sub.2 provide, respectively, the sensor signal S.sub.1 and
the difference signal D.sub.1 both in digital form. Both outputs
are connected to respective inputs of the digital signal processing
 The two temperature sensors 19 and 20 are likewise connected
to respective inputs of the signal processing unit DSP.
 The signal processing unit delivers, in known manner, on
plural outputs A.sub.1 A4 A5 the values of the mass flow rate,
the density and the temperature, respectively, of the fluid F. Additionally,
the signal processing unit DSP controls the exciter current, which
drives the oscillation excitation of the measuring tube 4 and the
amplification factor VF of the amplifier V.sub.2.
 The signal processing unit is additionally connected to
a concentration determining unit 210. In the concentration determining
unit 210 density and temperature of the fluid are evaluated. The
concentration determining unit 210 is connected to a display unit
AE for displaying the desired concentration value. Besides presenting
the concentration value in the display unit AE, a transmitting of
the concentration value to a superordinated evaluating unit (not
shown in further detail) is also possible.
 The concentration determining unit 210 stores a concentration
curve C as a function of density and temperature of the fluid. Input
of the current density value and the current temperature of the
fluid enables easy determination of the desired concentration.
 One possibility for storing the concentration curve is to
store the corresponding polynomial coefficients. The polynomial
coefficients can be easily determined by providing concentration
values for particular density and temperature values and conducting
a corresponding polynomial approximation.
 In the simplest case, this involves a two-dimensional polynomial.
1 c ( , ) = i = 0 M a i + i = 1 Z b i
 The polynomial degree of the density polynomial is preferably
M=4 the polynomial degree of the temperature polynomial Z=3.
 By entering various concentration values, a user can produce
a concentration specification tuned to one's application.