Calibration of current sensors by means of reference current during current measurement

• US 10,132,907 B2
• Filed: 09/17/2015
• Issued: 11/20/2018
• Est. Priority Date: 09/17/2014
• Status: Active Grant

• Current Assignee: Continental Automotive GmbH (Continental AG), Continental Teves AG & Co. OHG (Continental AG)
• Original Assignee: Continental Automotive GmbH (Continental AG), Continental Teves AG & Co. OHG (Continental AG)
• Inventors: Schramme, Martin, Jockel, Wolfgang
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): Rhodes-Vivour, Temilade
• Application Number:
  US15/505,216
• Publication Number:
  US 20170269184A1
• Time in Patent Office: 1,160 Days
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 27/16 Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence
• CPC Class Codes: G06F 1/00 Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00 architectures of general purpose stored program computers G06F15/76
• CPC Class Codes: G09G 1/00 Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of datacathode-ray oscilloscopes G01R13/20; radar display arrangements G01S7/04; display of digital non-picture data in television systems H04N7/0255
• CPC Class Codes: G11C 5/00 Details of stores covered by group G11C11/00

Abstract

A method for calibrating a current sensor which is configured to determine, in a vehicle'"'"'s onboard power system, an electric operating current which flows through a measuring resistor, based on comparison of a voltage drop at the measuring resistor caused by the operating current and based on a rule which is dependent on the measuring resistor, including: determining an operating voltage drop brought about at the measuring resistor by the operating current; impressing a known electric calibration current into the measuring resistor, detecting an overall voltage drop brought about at the measuring resistor by the calibration current and the operating current, filtering the operating voltage drop from the overall voltage drop, such that a calibration voltage drop which is brought about by the calibration current remains, and calibrating the rule, dependent on the measuring resistor, based on the comparison of the calibration current and the calibration voltage drop.

Claims

1. A method for calibrating a current sensor that is set up to determine, in an onboard power supply system of a vehicle, an electric operating current flowing through a measuring resistor based on a comparison of a voltage drop across the measuring resistor brought about by the operating current and a rule dependent on the measuring resistor, comprising:

determination of an operating voltage drop brought about across the measuring resistor by the operating current;

impression of a known electric calibration current into the measuring resistor,

detection of a total voltage drop brought about across the measuring resistor by the calibration current and the operating current,

filtering of the operating voltage drop from the total voltage drop, so that a calibration voltage drop brought about by the calibration current remains, and

calibration of the rule dependent on the measuring resistor based on a comparison of the calibration current and the calibration voltage drop,

wherein;

a) the calibration current is a current pulse having a pulse width,

b) the operating voltage drop is detected by detecting at least two operating voltage measured values at at least two measurement times positioned on opposites sides of the current pulse, such that the current pulse lies between the operating voltage measured values, and

c) at a middle time between the measurement times a mean value is formed between these at least two operating voltage measured values and used to determine the operating voltage drop for calibrating the current sensor, wherein the total voltage drop, the operating voltage drop and the calibration voltage drop are determined at the middle time.

2. The method as claimed in claim 1, wherein the total voltage drop and the operating voltage measured values are buffer-stored and each converted into a digital value at staggered times using a common analog-to-digital converter.

3. The method as claimed in claim 2, wherein a buffer store is provided for the total voltage drop and one buffer store is provided for each of the operating voltage measured values, and another measured value is stored in another buffer store during the actual reading of one of the buffer stores.

4. The method as claimed in claim 3, wherein the read signals for reading the buffer stores are longer than measured value signals for reading into the buffer store.

5. An apparatus that performs a method as claimed in claim 1.

6. A current sensor for measuring an electric current, comprising:

an electrical measuring resistor via which the electric current to be measured is routable, and

an apparatus as claimed in claim 5 for determining the electric current based on the operating voltage dropped across the electrical measuring resistor and the predetermined rule and for calibrating the rule.

7. A method for calibrating a current sensor that is set up to determine, in an onboard power supply system of a vehicle, an electric operating current flowing through a measuring resistor based on a comparison of a voltage drop across the measuring resistor brought about by the operating current and a rule dependent on the measuring resistor, comprising:

determination of an operating voltage drop brought about across the measuring resistor by the operating current;

impression of a known electric calibration current into the measuring resistor,

detection of a total voltage drop brought about across the measuring resistor by the calibration current and the operating current,

filtering of the operating voltage drop from the total voltage drop, so that a calibration voltage drop brought about by the calibration current remains, and

calibration of the rule dependent on the measuring resistor based on a comparison of the calibration current and the calibration voltage drop,

wherein;

a) the calibration current is a current pulse having a pulse width,

b) the operating voltage drop is detected by detecting at least two operating voltage measured values that lie outside the current pulse and the current pulse lies between the operating voltage measured values, and

c) a mean value is formed between these at least two operating voltage measured values, and

wherein the total voltage drop and the operating voltage measured values are each converted into a digital value using a separate analog-to-digital converter each and are each stored in a separate memory, the analog-to-digital converters being interchanged with one another at intervals of time.

8. A method for calibrating a current sensor that is set up to determine, in an onboard power supply system of a vehicle, an electric operating current flowing through a measuring resistor based on a comparison of a voltage drop across the measuring resistor brought about by the operating current and a rule dependent on the measuring resistor, comprising:

determination of an operating voltage drop brought about across the measuring resistor by the operating current;

impression of a known electric calibration current into the measuring resistor,

detection of a total voltage drop brought about across the measuring resistor by the calibration current and the operating current,

filtering of the operating voltage drop from the total voltage drop, so that a calibration voltage drop brought about by the calibration current remains, and

calibration of the rule dependent on the measuring resistor based on a comparison of the calibration current and the calibration voltage drop,

wherein;

a) the calibration current is a current pulse having a pulse width,

b) the operating voltage drop is detected by detecting at least two operating voltage measured values that lie outside the current pulse and the current pulse lies between the operating voltage measured values, and

c) a mean value is formed between these at least two operating voltage measured values,

wherein the total voltage drop brought about across the measuring resistor by the calibration current and the operating current is amplified by at least one amplifier stage,

wherein the amplifier stage has at least one upstream chopper circuit that converts the signal from the total voltage drop into an AC signal, wherein the polarity of the signal from the total voltage drop is periodically interchanged, and

wherein the operation and/or clocking of the chopper circuit is designed such that within an interval of time, bounded by the times at which the two operating voltage measured values that are detected outside the current pulse are determined, no polarity change and/or period change for the chopper circuit is performed.

9. The method as claimed in claim 8, wherein determination of the operating voltage drop from the total voltage drop involves using a dechopper element, and determination of the calibration voltage drop involves no dechopper element being used, but rather an intermediate tap is provided downstream of a first amplifier and all measured values tapped off from the intermediate tap are tapped off in a pulse period of the chopper signal.