Measuring and testing – Volume or rate of flow – Mass flow by imparting angular or transverse momentum to the...
Patent
1982-01-20
1984-08-28
Ruehl, Charles A.
Measuring and testing
Volume or rate of flow
Mass flow by imparting angular or transverse momentum to the...
73 3, 377 21, 417 63, G01F 100
Patent
active
044676573
DESCRIPTION:
BRIEF SUMMARY
Technical field
The present invention relates to a device for measuring the amount of flow and/or the speed of flow of a medium which is pumped by means of a pump unit, which device comprises a drive motor to cause working cycles of the pump unit, a pick-off for detecting said working cycles and transmitting a pick-off signal depending on said working cycles, an electronic unit to record, by means of said pick-off signal, a value proportional to the number of working cycles from which value the amount flowing through and/or the speed of flow can be determined by means of a nominal calibration factor fixed for the pump unit.
Background art
The measuring of the amount and/or the speed of flow in a medium which is pumped in a conduit hitherto had to be effected by means of separate flowmeters when it was necessary to meet strict requirements with regard to the measuring accuracy. In this case, these flowmeters are coupled into the conduit in series with a necessary pump unit. Such flowmeters are very expensive since they usually involve a high cost price and entail a complicated and expensive installation as well as requiring a great deal of service. It is also known, however, to measure the amount flowing through and the speed of flow of a medium by measuring the pump movements carried out starting from given pump data, which is possible with pumps of the so-called displacement type, such as gear pumps, impeller pumps and the like. With pumps of the rotating type, this is effected by means of a pick-off which is mounted on the pump shaft and which is adapted to deliver a signal depending on the rotation of the pump shaft, that is to say the number of revolutions effected or the speed of rotation of the shaft. Guided by nominal data for the pump in question, that is to say specified amounts per revolution according to the manufacturing data, the amount pumped or the speed of flow can thus be measured and utilized to control the drive motor of the pump, that is to say the stop function in a proportioning pump or control of the number of revolutions per minute.
The technical problem:
Nevertheless it has been found that a satisfactory measuring accuracy could not be achieved by the technique hitherto known, because nominal pump data do not coincide with actual data for the pump with regard to the amount pumped per revolution due to the fact that this value is influenced by a number of parameters which vary from case to case. Thus considerable errors appear in this approximate measurement, caused, inter alia, by the pressure in the conduit, the viscosity of the pumped medium, and wear in the pump unit.
The object of the present invention is to improve the last-mentioned type of measuring technique so as to obtain a satisfactory measuring accuracy.
The solution:
Said object is achieved by means of a device according to the invention which is characterized in that the electronic unit includes on the one hand a calibrating unit which can be adjusted to convert said pick-off signal into at least one ouput signal which represents a certain true calibration factor, calculated on the basis of a certain correction factor for correction of the nominal calibration factor, and on the other hand devices for recording the amount and/or speed of flow of the medium flowing through, adapted to be controlled by the output signal from the calibrating unit.
Brief description of drawings:
The invention will be described in more detail below with an example of embodiment with reference to the accompanying drawings in which;
FIG. 1 shows diagrammatically a pump unit with a measuring and control device according to the invention;
FIG. 2 shows, likewise diagrammatically, the principle on which the present device is based, according to the invention;
FIG. 3 shows an example of an electronic unit included in the device shown in FIG. 1;
FIG. 4 shows an amount calculating unit which is included in the electronic unit shown in FIG. 3;
FIG. 5 shows a calibrating unit which is likewise included in the electronic unit shown in FIG. 3;
FIG.
REFERENCES:
patent: 3873814 (1975-03-01), Mirdadian
patent: 4331262 (1982-05-01), Snyder et al.
Ruehl Charles A.
Telfa Jabsco AB
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