Electromagnetic flowmeter
First Claim
1. An electromagnetic flowmeter comprising:
- a measuring pipe through which a conductive fluid to be measured can flow;
at least one excitation coil for applying, upon reception of an excitation current, a magnetic flux corresponding to the excitation current to the fluid in the measuring pipe;
electrodes for detecting the electromotive force induced in the fluid due to a mutual effect by the fluid and the magnetic flux applied to the fluid by said excitation coil;
noise detection means for detecting, upon reception of the electromotive force detected by said electrodes, the noise included in the electromotive force;
excitation current supply means for alternately and selectively supplying, upon reception of an output signal from said noise detection means, one of at least two excitation currents which have different frequencies to said excitation coil every predetermined period when said noise detection means detects no noise, and for supplying one excitation current whose frequency is farthest from the frequency of the noise when said noise detection means detects the noise; and
flow rate detection means for calculating, upon reception of the electromotive force detected by said electrode, the flow rate of the fluid based upon the electromotive force.
1 Assignment
0 Petitions
Accused Products
Abstract
Excitation coils apply a magnetic flux corresponding to the excitation current to a fluid. An electromotive force induces in the fluid and the amplified electromotive force is supplied to first and second filter circuits. The first circuit generates a predetermined signal upon reception of a signal of a frequency higher than a first frequency. The second circuit generates a predetermined signal upon reception of a signal of a frequency lower than a second frequency which is lower than the first frequency. The contents of a flip-flop are inverted at every given period. A selection circuit outputs one of signals having the first and second frequencies as an excitation signal in response to the contents of the flip-flop. In response to the excitation signal, an exciting circuit selectively supplies to excitation coils a first excitation current of a frequency higher than the first frequency and a second excitation current of a frequency lower than the second frequency. When the exciting circuit outputs the first excitation current and the second circuit generates the predetermined signal, and when the exciting circuit outputs the second excitation current and the first circuit generates the predetermined signal. Thereby the control circuit prevents the flip-flop from being inverted.
-
Citations
11 Claims
-
1. An electromagnetic flowmeter comprising:
-
a measuring pipe through which a conductive fluid to be measured can flow; at least one excitation coil for applying, upon reception of an excitation current, a magnetic flux corresponding to the excitation current to the fluid in the measuring pipe; electrodes for detecting the electromotive force induced in the fluid due to a mutual effect by the fluid and the magnetic flux applied to the fluid by said excitation coil; noise detection means for detecting, upon reception of the electromotive force detected by said electrodes, the noise included in the electromotive force; excitation current supply means for alternately and selectively supplying, upon reception of an output signal from said noise detection means, one of at least two excitation currents which have different frequencies to said excitation coil every predetermined period when said noise detection means detects no noise, and for supplying one excitation current whose frequency is farthest from the frequency of the noise when said noise detection means detects the noise; and flow rate detection means for calculating, upon reception of the electromotive force detected by said electrode, the flow rate of the fluid based upon the electromotive force. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. An electromagnetic flowmeter comprising:
-
a measuring pipe through which a fluid to be measured can flow; at least one excitation coil for applying, upon reception of an excitation current, a magnetic flux corresponding to the excitation current to the conductive fluid flowing through said pipe; electrodes for detecting an electromotive force induced in the fluid by a mutual effect of the magnetic flux applied to the conductive fluid and the fluid itself; a first filter circuit, connected to said electrode, for receiving the electromotive force detected by said electrodes and generating a predetermined signal upon reception of a signal of a frequency equal to or higher than a first frequency; a second filter circuit, connected to said electrode, for receiving the electromotive force detected by said electrodes and generating a predetermined signal upon reception of a signal of a frequency equal to or lower than a second frequency which is lower than the first frequency; flip-flop means whose content is inverted at every given period; supply means for selectively supplying to said excitation coil a first excitation current of a frequency equal or higher than the first frequency and a second excitation current of a frequency equal or lower than the second frequency in response to an output signal from said flip-flop means; control means, connected to said first and second filter circuits and responsive to the output signals therefrom, for detecting the predetermined signal from said second filter circuit, when said excitation current supply means supplies the first excitation current to said excitation coil and said second filter circuit generates the predetermined signal, and for detecting the predetermined signal from said first filter circuit, when said excitation current supply means supplies the second excitation current to said excitation coil and said first filter circuit supplies the predetermined signal, thereby preventing said flip-flop means from being inverted; and flow rate detection means, connected to said electrode, for sampling the electromotive force detected by said electrodes so as to obtain the flow rate of the fluid based upon the sample value.
-
Specification