Circuit arrangement for the power supply of a two-wire sensor

• US 6,897,639 B2
• Filed: 08/15/2002
• Issued: 05/24/2005
• Est. Priority Date: 09/19/2001
• Status: Expired due to Fees

• Current Assignee: VEGA Grieshaber KG (Grieshaber Verwaltungsgesellschaft mbH)
• Original Assignee: VEGA Grieshaber KG (Grieshaber Verwaltungsgesellschaft mbH)
• Inventors: Woehrle, Albert, Koernle, Ralf, Motzer, Juergen
• Primary Examiner(s): Han, Jessica
• Application Number:
  US10/218,629
• Publication Number:
  US 20030052657A1
• Time in Patent Office: 1,013 Days
• Field of Search: 323/274, 323/275, 323/277, 323/280, 323/324, 323/908, 324/771, 324/537, 361/87, 361/93.9
• US Class Current: 323/277
• CPC Class Codes: G05F 3/18 using Zener diodes
• CPC Class Codes: H02H 9/008 Intrinsically safe circuits
• CPC Class Codes: Y10S 323/908 Inrush current limiters

Abstract

A two-wire sensor (6) is attached to one pole of a voltage distribution source (U) by an initial connecting line (V1) in which a current-limiting resistor (R1) is positioned and is attached to the other pole by a second connecting line (V2). Parallel to the series connection consisting of the two-wire sensor (S) and the current-limiting resistor (R1) is at least one limiting diode (D1). A current regulator (SR) which is attached to the poles of the power source (U) regulates a parallel current (I) which runs parallel to the current through the two-wire sensor (D), so that there is a sum current at the poles of the power source (U) that always corresponds to the measured value delivered by the two-wire sensor (S). The regulating inputs of the current regulator (SR) are connected to the terminals of a current-sensing resistor (R2) positioned in a connecting line (V1). When a HART®-interface is used with the two-wire sensor (S) a HART®-resistor (RH) is positioned in one of the two connecting lines (V1).

Claims

1. A circuit arrangement for providing voltage to a two-wire sensor (S) which is attached to a power source (U) at a first pole by an initial connecting line (V1) in which a current-limiting resistor (R1) is positioned and which a two-wire sensor (S) is attached to the power source at a second pole by a second connecting line (V2), while at least one limiting diode (D1) is positioned parallel to the two-wire sensor (S) and the current-limiting resistor (R1), wherein

the two poles of the power source (U) are connected by a current regulator (SR) having regulating inputs and in one of the two connecting lines (V1) a current sensor (R2) is positioned whose terminals are connected to the regulating inputs of the current regulator (SR).

2. A circuit arrangement according to claim 1, wherein the current-limiting resistor (R1) also serves as a current sensor.

3. A circuit arrangement according to claim 1, wherein the current sensor (R2) is a current-sensing resistor.

4. A circuit arrangement according to claim 3, wherein

said first pole of the power source (U) is connected to one of the terminals of the two-wire sensor (S) by connecting line (V1) in which connecting line (V1) is positioned as a series connection consisting of the current-sensing resistor (R2) and the current-limiting resistor (R1), while the other terminal of the two-wire sensor (S) is connected by the second connecting line (V2) to the second pole of the power source (U);

said first pole of the power source (U) is connected to the second pole of the power source (U) by a series connection consisting of a diode (D2) and an initial resistor (R6);

said first pole of the power source (U) is connected by a second resistor (R3) to a drain electrode of a field-effect transistor (T1) having a source electrode connected to the second connecting line (V2);

the shared node of the diode (D2) and the first resistor (R6) is connected by a third resistor (R5), and the drain electrode of the field-effect transistor (T1) is connected by a fourth resistor (R4) to the inverted input of an operational amplifier (OP) whose non-inverted input is connected to the shared node of the current-limiting resistor (R1) and the current-sensing resistor (R2) and wherein an outlet is attached to a gate electrode of the field-effect transistor (T1).