Arrangement for generating DC magnetic fields of alternating polarity for the magnetic-inductive flow measurement

• US 4,410,926 A
• Filed: 08/06/1982
• Issued: 10/18/1983
• Est. Priority Date: 10/02/1980
• Status: Expired due to Term

• Current Assignee: Endress+Hauser Flowtec AG (Endress+Hauser AG)
• Original Assignee: Flowtec AG
• Inventors: Hafner, Peter, Flecken, Peter
• Primary Examiner(s): EISENZOPF, REINHARD
• Application Number:
  US06/406,061
• Time in Patent Office: 438 Days
• Field of Search: 361/100, 361/101, 361/93, 361/156, 363/55, 363/56, 363/57, 363/58, 363/86, 363/89, 318/341
• US Class Current: 361/93.9
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: H03K 17/04166 in bipolar transistor switches
• CPC Class Codes: H03K 17/64 having inductive loads
• CPC Class Codes: H03K 17/662 each output circuit comprising more than one controlled bipolar transistor

Abstract

An arrangement for generating DC magnetic fields of alternating polarity for the magnetic-inductive flow measurement by means of a field coil which is connected via alternately controlled switching members to a DC voltage source, wherein during the reversal time following the change-over of the switching members a capacitor is connected to the field coil to form a resonant circuit separate from the DC voltage source and the capacitance C of the capacitor in dependence upon the desired reversal time Δt has substantially the value ##EQU1## wherein L is the inductance and R the ohmic resistance of the field coil.

Claims

1. An arrangement for generating DC magnetic fields of alternating polarity for the magnetic-inductive flow measurement by means of a field coil which is connected via alternately controlled switching members to a DC voltage source, wherein during the reversal time following the change-over of the switching members a capacitor is connected to the field coil to form a resonant circuit separate from the DC voltage source and the capacitance C of the capacitor in dependence upon the desired reversal time Δ

t has substantially the value ##EQU7## wherein L is the inductance and R the ohmic resistance of the field coil.

2. An arrangement as defined in claim 1 wherein the field coil lies in the first diagonal of a bridge circuit to the second diagonal of which the DC voltage source is connected and in the four bridge branches of which switching members lie, the switching members lying in diametrically opposite bridge branches being rendered alternately conductive and non-conductive in pairs, and the capacitor is connected in parallel with the second bridge diagonal.

3. An arrangement as defined in claim 2 wherein between the connection point of the capacitor and the DC voltage source a switch member is inserted which blocks the connection during the reversal time.

4. An arrangement as defined in claim 3 wherein the switch member is a diode.

5. An arrangement as defined in any one of claims 2 to 4 wherein between the connection point of the capacitor and the DC voltage source a current regulator is inserted.

6. An arrangement as defined in claim 1 wherein each switching member is formed by a mechanical contact.

7. An arrangement as defined in claim 1 wherein each switching member is formed by a controllable electronic switch member.

8. An arrangement as defined in claim 7 wherein each electronic switch member is formed by a switch element conductive only in one direction and a diode connected oppositely poled parallel therewith.

9. An arrangement as defined in claim 8 wherein the controllable switch element is a transistor.

10. An arrangement as defined in claim 9 wherein the diode connected oppositely poled in parallel is a substrate diode.

11. An arrangement as defined in claim 8 wherein the controllable switch element is a thyristor.

12. An arrangement as defined in any one of claims 6 to 11 wherein the output voltage of the DC voltage source is increased during the reversal time.

13. An arrangement as defined in claim 1, comprising a DC voltage source having two output terminals supplying two output voltages of opposite polarity symmetrical with respect to the potential of a reference point, a first switching member connected between the first output terminal of said two output terminals and one terminal of said field coil, a second switching member connected between the second output terminal of said two output terminals and said one terminal of said field coil, the other terminal of said field coil being connected to said reference point, a first capacitor connected between said common reference point and the connection between said first switching member and said first output terminal, and a second capacitor connected between said common reference point and the connection between said second switching member and said second output terminal.

14. An arrangement as defined in claim 13, comprising a first switch member inserted between said first output terminal and the connection point of said first capacitor and a second switch member inserted between said second output terminal and the connection point of said second capacitor, each of said switch members blocking the connection during the reversal time.

15. An arrangement as defined in claim 14 wherein each switch member is a diode.

16. An arrangement as defined in claim 13 wherein in each connection between said one terminal of said field coil and the first and second output terminals of the DC voltage source a current regulator is inserted.

17. An arrangement as defined in claim 16 wherein each current regulator is formed by the corresponding switching member.

18. An arrangement as defined in claim 11 wherein the diode connected oppositely poled in parallel is a substrate diode.