Watchdog For Voltage Detector Display

• US 20130057409A1
• Filed: 09/05/2012
• Published: 03/07/2013
• Est. Priority Date: 09/05/2011
• Status: Active Grant

• Current Assignee: Fluke Corporation (Fortive Corp.)
• Original Assignee: Fluke Corporation (Fortive Corp.)
• Inventors: Rodehorst, Lutz
• Granted Patent: US 9,128,129 B2
• Time in Patent Office: Days
• US Class Current: 340/660
• CPC Class Codes: G01R 19/2503 for measuring voltage only, e.g. digital volt meters (DVM's) G01R19/2506 - G01R19/257 take precedence
• CPC Class Codes: G01R 35/00 Testing or calibrating of apparatus covered by the other groups of this subclass

Abstract

The present invention relates to a watchdog timer dedicated to the display controller of a voltage detector wherein the watchdog determines a malfunction in the microcontroller and triggers a visual warning to be displayed via the display controller. This prevents inaccurate voltage information from being displayed in the case of a microcontroller malfunction and thereby the user from being exposed to the risk of extreme injury through, for example, a high-voltage shock.

Claims

1. A voltage detector that detects voltage, the detector comprising:

a microcontroller configured to control writing of detected voltage values to a display,

the display configured to display detected voltage values;

a watchdog timer to determine a malfunction of the microcontroller, wherein the watchdog timer is configured to trigger a visual warning on the display, if a malfunction is determined.

2. The voltage detector of claim 1 wherein the watchdog timer is independent of the microcontroller.

3. The voltage detector of claim 1 wherein the display comprises a plurality of LEDs for indicating the detected voltage values and the visual warning comprises operation of all of the LEDs simultaneously.

4. The voltage detector of claim 1 further comprising a display controller to control the display, wherein the watchdog timer is configured to trigger the visual warning by triggering an asynchronous reset of the display controller.

5. The voltage detector of claim 4 wherein the asynchronous reset is triggered if a specific sequence of signals from the microcontroller is not received by the display controller within a predetermined time period.

6. The voltage detector of claim 5 wherein the display controller comprises a clock input configured to suppress signals sent from the microcontroller and received by the display controller after the predetermined time period.

7. The voltage detector of claim 6 wherein the display controller further comprises a clear input which may be set to a low level or a high level and wherein the clock input suppresses signals from the microcontroller a wait period after the clear input has been reset from the low level to the high level.

8. A method for a voltage detector comprising a display to display detected voltage values comprising:

using a watchdog timer to determine a malfunction of a microcontroller;

triggering a visual warning on the display if a microcontroller malfunction is determined by the watchdog timer.

9. The method of claim 8 wherein the watchdog timer is independent of the microcontroller.

10. The method of claim 8 wherein the display comprises a plurality of LEDs for indicating the detected voltage values and operating all of the LEDs simultaneously in order to display the visual warning.

11. The method of claim 8 further comprising providing a display controller to control the display, and triggering an asynchronous reset of the display controller by the watchdog timer in order to trigger the visual warning.

12. The method of claim 11 further comprising triggering the asynchronous reset if a specific sequence of signals from the microcontroller is not received by the watchdog timer within a predetermined time period.

13. The method of claim 12 further comprising using a clock input in the display controller to suppress signals sent from the microcontroller and received by the display controller after a predetermined time period.

14. The method of claim 13 further comprising:

providing a clear input in the display controller and resetting the clear input; and

using the clock input to suppress signals from the microcontroller received a wait period after the clear input has been reset.

15. A detector that detects data, the detector comprising:

a processor configured to control writing of detected data to a display,

the display configured to display data detected by the detector;

a watchdog timer to determine a malfunction of the processor, wherein the watchdog timer is configured to trigger a visual warning on the display, if a malfunction is determined.

16. The detector of claim 15 wherein the watchdog timer is independent of the processor.

17. The detector of claim 15 wherein the display comprises a plurality of LEDs for indicating the detected data and the visual warning comprises operation of all of the LEDs simultaneously.

18. The detector of claim 15 further comprising a display controller to control the display, wherein the watchdog timer is configured to trigger the visual warning by triggering an asynchronous reset of the display controller.

19. The detector of claim 18 wherein the asynchronous reset is triggered if a specific sequence of signals from the processor is not received by the display controller within a predetermined time period.

20. The detector of claim 19 wherein the display controller comprises a clock input configured to suppress signals sent from the processor and received by the display controller after the predetermined time period;

and a clear input which may be set to a low level or a high level and wherein the clock input suppresses signals from the processor a wait period after the clear input has been reset from the low level to the high level.