Flutter reduction apparatus and method

• US 7,230,418 B2
• Filed: 07/16/2004
• Issued: 06/12/2007
• Est. Priority Date: 07/16/2004
• Status: Active Grant

• Current Assignee: Auto Meter Products Incorporated
• Original Assignee: Auto Meter Products Incorporated
• Inventors: Schubert, Thomas A.
• Primary Examiner(s): Lefkowitz; Edward
• Assistant Examiner(s): WHITTINGTON, KENNETH
• Application Number:
  US10/892,370
• Publication Number:
  US 20060012361A1
• Time in Patent Office: 1,061 Days
• Field of Search: 324160-180, 116/284
• US Class Current: 324/167
• CPC Class Codes: G01P 1/04 Special adaptations of driving means
• CPC Class Codes: G01P 1/07 Indicating devices, e.g. for remote indication indicating working conditions of vehicles G07C5/00
• CPC Class Codes: G01P 3/44 for measuring angular speed G01P3/56 takes precedence

Abstract

A tachometer circuit includes a flutter reduction circuit and a tachometer. The tachometer circuit cancels pointer flutter in the tachometer without adversely affecting pointer response.

Claims

1. A tachometer circuit comprising:

a tachometer; and

a flutter reduction circuit electrically coupled to and driving said tachometer, said flutter reduction circuit generating a voltage to cancel ripple voltages;

wherein said flutter reduction circuit including a high pass filter circuit; and

a tachometer driver circuit electrically coupled to said high pass filter circuit, said high pass filter circuit filtering the unwanted input voltages and generating the voltage to cancel ripple voltages; and

said high pass filter circuit further includes an operational amplifier, said operational amplifier is biased by a bias signal from said driver circuit; and

a voltage divider electrically coupled to said operational amplifier.

2. The tachometer circuit of claim 1, wherein said voltage divider further comprises two resistors in connected series.

3. The tachometer circuit of claim 1, wherein said operational amplifier outputs the voltage that is used to cancel rippled voltages.

4. The tachometer circuit of claim 1, wherein the tachometer is an aircore tachometer.

5. The tachometer circuit of claim 1, wherein said tachometer is an aircore mini-meter.

6. The tachometer circuit of claim 1, wherein the tachometer is a motorcycle tachometer.

7. The tachometer circuit of claim 1, wherein said high pass filter is connected to a charge pump filter capacitor.

8. The tachometer circuit of claim 1, wherein a divider ratio for the voltage divider is approximately 10/47.

9. The tachometer circuit of claim 1, further including input circuitry connected to said tachometer driver circuit.

10. The tachometer circuit of claim 1, further including a one shot circuit connected to said tachometer driver circuit.

11. A flutter reduction circuit for use with a tachometer, said flutter reduction circuit comprising:

a high pass filter circuit; and

a driver circuit electrically coupled to said high pass filter circuit, said high pass filter circuit passing unwanted input signals to a first circuit within the driver adapted to cancel out the signals and said high pass filter circuit generating a voltage to cancel ripple voltages; and

wherein said high pass filter circuit further comprises;

an operational amplifier; and

a voltage divider electrically coupled to said operational amplifier.

12. The tachometer circuit of claim 11, further including a one shot circuit connected to said driver circuit.

13. The flutter reduction circuit of claim 11, wherein said voltage divider further comprises two resistors in connected series.

14. The flutter reduction circuit of claim 11, wherein said operational amplifier outputs the voltage that is used to cancel rippled voltages.

15. The flutter reduction circuit of claim 11, wherein said operational amplifier is biased by a bias signal from said driver integrated circuit.

16. The flutter reduction circuit of claim 11, wherein the flutter reduction circuit connects to an aircore tachometer.

17. The flutter reduction circuit of claim 11, wherein the flutter reduction circuit connects to an aircore mini-meter.

18. The flutter reduction circuit of claim 11, wherein the flutter reduction circuit connects to a motorcycle tachometer.

19. The tachometer circuit of claim 11, wherein said high pass filter is connected to a charge pump filter capacitor.

20. The flutter reduction circuit of claim 11, further including input circuitry connected to said driver circuit.