Electromagnetic flowmeter

• US 5,388,465 A
• Filed: 11/17/1992
• Issued: 02/14/1995
• Est. Priority Date: 11/17/1992
• Status: Expired due to Term

• Current Assignee: Yamatake Corporation
• Original Assignee: Yamatake-Honeywell Company Limited
• Inventors: Okaniwa, Hiroshi, Koshimizu, Atsushi, Mitsutake, Ichiro
• Primary Examiner(s): Goldstein, Herbert
• Assistant Examiner(s): Dougherty, Elizabeth L.
• Application Number:
  US07/978,088
• Time in Patent Office: 819 Days
• Field of Search: 73/861.12, 73/861.16, 73/861.17
• US Class Current: 73/861.17
• CPC Class Codes: G01F 1/60 Circuits therefor

Abstract

In an electromagnetic flowmeter for obtaining a signal corresponding to flow rate of conductive fluid in a magnetic field, a noise detector detects a noise superimposed on the fluid, and a timing signal generator produces timing of generating an exciting current to produce the magnetic field and timing of sampling electrical potential generated in electrodes in the fluid, based on the noise detected by the noise detector.

Claims

1. An electromagnetic flowmeter for detecting a signal corresponding to flow rate of a conductive fluid in an imposed magnetic field by sampling electrical potential generated at electrodes submerged in said fluid, which comprises:

a noise detection means for detecting noise superimposed on said fluid from said electrodes to produce a noise signal; and

a timing signal generation means for generating timing of an exciting current for generating said magnetic field and timing of said sampling, wherein said timing signal is generated in synchronization with said noise signal and wherein said timing of said sampling is generated at a fixed delay subsequent to a change in polarity of said exciting current.

2. The electromagnetic flowmeter according to claim 1, which further comprises a pseudo-noise generation means for sending a pseudo-noise signal substantially synchronous with said noise signal to said timing signal generation means when said noise signal is not detected by said noise detection means.

3. An electromagnetic flowmeter for detecting a signal corresponding to flow rate of conductive fluid in an imposed magnetic field by sampling electrical potential generated in electrodes submerged in said fluid, which comprises:

a noise detection means for detecting noise superimposed on said fluid from said electrodes to produce a noise signal;

a detector logic means for determining whether or not said noise signal exists;

a delay means for delaying transmission of said noise signal by a predetermined period;

a pseudo-noise generation means for generating a pseudo-noise signal synchronized with said predetermined period when said detector logic means determines that said noise signal is not present; and

a timing signal generation means for generating timing of an exciting current for generating said magnetic field and timing of said sampling, wherein said timing signal of said exciting current is generated in substantially constant synchronization with change in polarity of said noise signal or said pseudo-noise signal.

4. An electromagnetic flowmeter for detecting a signal corresponding to flow rate of conductive fluid in an imposed magnetic field by sampling electrical potential generated at electrodes submerged in said fluid, which comprises:

a noise detection means for detecting a noise superimposed on said fluid to transmit a noise signal;

a filter means for picking up only the commercial power supply frequency component from said noise signal;

a pulse generation means for generating a timing pulse at each polarity change of every half period of said commercial power supply frequency in response to an input signal of said commercial power supply frequency picked up by said filter means;

a pseudo-noise generation means for generating a pseudo-noise signal synchronous with same period as said noise signal when said noise detection means does not transmit said noise signal; and

a timing signal generation means for generating timing of an exciting current for generating said magnetic field and timing of said sampling, delayed for a fixed period after said timing pulse generated by either said pulse generation means or said pseudo-noise signal generated by said pseudo-noise generation means.

5. An electromagnetic flowmeter for detecting a signal corresponding to flow rate of conductive fluid in a magnetic field by sampling with a predetermined timing electrical potential generated in electrodes submerged in said fluid, which comprises:

a noise detection means for detecting a noise superimposed on said fluid at said electrodes to transmit a noise signal;

a timing detection means for detecting the commercial power supply frequency from said noise signal to transmit as a timing detection signal one shot pulse signal every half period of said commercial power supply frequency;

a standard timing signal output means for transmitting as a standard timing signal a pulse that becomes "High" for a fixed duration within an interval from a time of one pulse signal transmission to a time of the following pulse signal transmission;

a logical product means for making logical product of said timing detection signal transmitted by said timing detection means and said standard timing signal transmitted by said standard timing signal output means;

a pseudo-signal generation means for generating a pseudo-signal with same frequency as the noise signal when said noise detection means does not transmit said noise signal; and

a timing signal generation means for generating timing of producing an exciting current for generating said magnetic field and timing of said sampling, triggered by a pulse signal output from said logical product means or a pseudo-signal output from said pseudo-signal generation means.