ADJUSTABLE LINEARITY ELECTRONIC TACHOMETER WITH PEAK READOUT

• US 3,822,402 A
• Filed: 07/31/1972
• Issued: 07/02/1974
• Est. Priority Date: 07/31/1972
• Status: Expired due to Term

• Current Assignee: Gary W. Vest
• Original Assignee: Gary W. Vest
• Inventors: Vest, Gary W.
• Primary Examiner(s): Lynch, Michael J.
• Application Number:
  US05/276,523
• Time in Patent Office: 701 Days
• Field of Search: 324/166,168,169,170,173,174,175,162,78J,78E,161,102,103,111 328/140 307/271,230,233,304
• US Class Current: 324/169
• CPC Class Codes: G01P 3/4805 by using circuits for the electrical integration of the generated pulses measuring impulse frequency by integration G01R23/09
• CPC Class Codes: G01P 3/4807 by using circuits for the detection of the pulses delivered by the ignition system of an internal combustion engine

Abstract

An improved tachometer for measuring and indicating the speed rate of an internal combustion engine having an electrical ignition system. Electrical pulses from the ignition system are used to energize a transistor that switches on and off in response to each ignition pulse. The resulting square wave pulses in the transistor circuit are filtered to provide a D.C. voltage that varies non-linearly with engine speed. The D.C. voltage is impressed across a field-effect transistor with a response characteristic that varies non-linearly in a manner that balances the non-linearity of the D.C. voltage variation to produce a voltage acorss a meter, that varies essentially linearly or in an otherwise controlled manner with engine speed. A '"'"''"'"''"'"''"'"'memory'"'"''"'"''"'"''"'"' capacitor may be connected in parallel with the field-effect transistor input to be charged to a level representative of the maximum voltage impressed across the field-effect transistor input in response to the ignition system impulses and then at a later time be switched into the field-effect transistor input circuit to provide a meter readout of the stored maximum signal.

Claims

1. In a device for converting a train of electrical pulses with a frequency representative of an engine speed, into a voltage signal that varies predictably with the engine speed, including a direct current voltage source, and a circuit connected to said voltage source responsive to said engine speed pulses for providing uniform operating pulses at the frequency of said engine speed pulses, the improvement which comprises:

circuit means connected to said circuit for converting said operating pulses into a voltage signal with a level that varies non-linearly with engine speed, a field-effect transistor connected to receive its input from said circuit means for producing a resulting signal, and means for biasing said field-effect transistor into having a response characteristic that varies non-linearly with voltage level in a manner such that said resulting signal varies essentially linearly with engine speed.

2. A device as defined in claim 1 including a milliammeter connected to said field-effect transistor for receiving said resulting signal.

3. A device as defined In claim 2 wherein said circuit means includes a memory capacitor adapted to be charged by said signal voltage to a level representative of the maximum engine speed achieved in an interval of engine operation and switch means for selectively connecting said capacitor to the input of said field-effect transistor.

4. A device as defined in claim 1 including means for adjusting the nonlinearity of said voltage signal level as a function of engine speed.

5. A device as defined in claim 1 including means for expanding said voltage signal within a defined range while simultaneously suppressing said voltage signal level in other ranges above or below said defined range.

6. A device as defined in claim 5 including a milliammeter means for displaying said voltage expansion and suppression.

7. A device as defined in claim 1 wherein said circuit means includes an output suitable for operating voltage actuated control devices.

8. A device as defined in claim 7 wherein said circuit means includes an output suitable for operating voltage actuated control devices, wherein said voltage actuated control devices would include means for regulating engine speed.

9. A tachometer for converting an electrical pulse train signal representative of an engine speed into a voltage level that varies linearly with the engine speed rate, comprising:

a milliammeter, a direct current voltage source, a circuit connected to said voltage source responsive to said electrical pulse train for producing uniform operating pulses at the frequency of said electrical pulse train, circuit means connected to said circuit for converting said operating pulses to a voltage signal with a level that varies non-linearly with engine speed, a field-effect transistor receiving its input from said circuit means and delivering its output to said meter, and means for biasing said field-effect transistor into having a response characteristic that varies non-linearly with voltage level in a manner such that the input supplied to said milliammeter varies linearly with engine speed.

10. A tachometer as defined in claim 9 in combination with an internal combustion engine electrical ignition system.

11. In an electronic tachometer for an internal combustion engine having an electrical ignition system and a direct current voltage source, the tachometer having a milliammeter, a circuit connected to said voltage source and responsive to electrical pulses from the ignition system at a frequency representative of the speed rate to be measured for producing uniform operating pulses at the frequency of said electrical pulses, and circuit means connected between said circuit and said milliammeter for converting said operating pulses to a voltage signal representative of engine speed, to be applied to said milliammeter, the improvement which comprises:

a memory capacitor in said circuit means, adapted to be charged by said signal voltage to a level representative of the maximum engine speed achieved in an interval of engine operation, switch means for measuring the charge on said capacitor using said milliammeter, a diode in said circuit means through which said memory capacitor is charged, said diode being adapted to assure that the charge developed on said memory capacitor is at the same level as said engine speed voltage signal, and means for cancelling out the forward voltage drop across said diode when the voltage stored across said memory capacitor is measured by said meter in response to actuation of said switch means.

12. A tachometer as defined in claim 11 including means for cancelling out errors caused by radio frequency interference.