Inductive flow meter
AssigneeTurbo-Werk Messtechnik GmbH
InventorFriedhelm Doll
Life of this patent
Estimating the term…
Abstract
In an inductive flow meter, the magnetic field generator (11), provided for generating a magnetic field within a tube (10), is connected to a alternating current voltage source via an electronic switch (13). The switch (13) is controlled in such a manner that it becomes conducting only at a zero crossing of the alternating current, respectively, and subsequently remains in the conducting state until the next zero crossing of the exciting current (i) occurs. The useful voltage received at the electrodes (16a, 16b) is integrated in an integrator (19) whereby the noise voltage, coupled into the electrode loop by self-induction, is zero because of ##EQU1##
Claims17
An inductive flow meter, comprising:
- a magnetic field generator connectable to an alternating current voltage,
- a pair of electrodes,
- an evaluating circuit connected to said electrodes,
- a control circuit provided with a zero crossing detector for detecting the zero crossings of the alternating current voltage, and
- an electronic switch connecting the magnetic field generator to the alternating current voltage, which electronic switch is controlled by the control circuit in such a manner that it becomes conducting only at a zero crossing of the alternating current voltage and is switched out at a zero crossing of the exciting current,
- characterized in that the electronic switch supplies the alternating current voltage to the magnetic field generator each time for less than one period length and that the evaluating circuit includes an integrator which, starting with the conducting state of the switch, integrates the electrode voltage over one period length of the alternating current or a multiple thereof.
An inductive flow meter, comprising:
- a magnetic field generator,
- a pair of electrodes,
- a switch for connecting the magnetic field generator to a source of alternating current voltage, whereby the alternating current voltage is supplied to the magnetic field generator and an exciting current is supplied to the magnetic field generator,
- a control circuit, the control circuit including a zero crossing detector for detecting a zero amplitude of the alternating current voltage, means for bringing the switch to a conductive state at a zero amplitude of the alternating current voltage, and means for bringing the switch to a non-conductive state at a zero amplitude of the exciting current,
- means for controlling the switch to supply the alternating current voltage to the magnetic field generator for a duration less than a period of the alternating current voltage, and
- an evaluating circuit connected to the pair of electrodes, the evaluating circuit including an integrator for integrating a voltage at the electrodes over a period of time beginning when the switch is brought to the conductive state and corresponding to at least a period of the alternating current voltage.
Dependencies are inferred from the claim text.