Self-calibrating device for measuring voltage and corresponding method

• US 20050248351A1
• Filed: 05/09/2005
• Published: 11/10/2005
• Est. Priority Date: 05/07/2004
• Status: Abandoned Application

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Graf, Hans-Michael
• Application Number:
  US11/125,550
• Publication Number:
  US 20050248351A1
• Time in Patent Office: Days
• US Class Current: 324/433
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• 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: H03F 2200/261 Amplifier which being suitable for instrumentation applications

Abstract

A device for measuring a battery voltage is a self-calibrating device. The battery voltage is connected to a voltage divider formed of series-connected resistors, or components that are subject to a voltage drop. For the purposes of calibration the voltage divider is separated from the battery voltage and a reference current or reference voltage source is connected to the voltage divider in its place. The voltages dropping across the voltage divider are measured and an actual resistance ratio of the resistors of the voltage divider is calculated, based on the measured voltages. The voltage divider is then re-connected to the battery voltage that is to be measured and a battery voltage is determined with the aid of the voltage divider, taking into account the calculated resistance ratio.

Claims

1. A device for measuring voltage, comprising:

a voltage divider formed by series-connected resistors R₃, R₄ for measuring a battery voltage V₀;

a first switch having an open position disconnecting the battery voltage from said voltage divider;

a second switch having a closed position connecting a reference current source or a reference voltage source to said voltage divider;

a measuring device connected to said voltage divider for measuring respective voltages dropping across said voltage divider; and

a calculating device connected to said measuring device and configured to calculate an actual resistance ratio of said resistors R₃, R₄ of said voltage divider based on the measured voltages when said second switch is in the closed position, and an actual battery voltage based on the calculated resistance ratio.

2. The device according to claim 1, wherein at least one of said series-connected resistors is a component across which voltage drops.

3. The device according to claim 1, which further comprises a temperature sensor for recording a current temperature value, and wherein said calculating device is configured to calculate the resistance ratio of said resistors of said voltage divider at predetermined temperature values and to determine an actual battery voltage based on the resistance ratio at the temperature.

4. The device according to claim 3, which further comprises a memory for storing the resistance ratio calculated for a given temperature.

5. A method of automatically calibrating a voltage measuring device, which comprises the following method steps:

connecting a reference current or reference voltage source to a voltage divider and measuring respective voltages dropping across the voltage divider;

calculating an actual resistance ratio of the resistors of the voltage divider based on the voltages measured in the measuring step; and

determining a battery voltage V_{0 with the voltage divider, taking into account the resistance ratio calculated in the calculating step.}

6. The method according to claim 5, which comprises measuring a temperature T and performing the connecting, calculating, and determining steps at predetermined temperatures.

7. The method according to claim 6, which comprises storing a resistance ratio of the resistors of the voltage divider, wherein the resistance ratio has been calculated for a specific temperature.