Method and apparatus for time based measurement of impedance

• US 4,546,441 A
• Filed: 07/22/1982
• Issued: 10/08/1985
• Est. Priority Date: 07/22/1982
• Status: Expired due to Fees

• Current Assignee: John Burch
• Original Assignee: John Burch
• Inventors: Burch, John
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): Woo, Louis
• Application Number:
  US06/400,911
• Time in Patent Office: 1,174 Days
• Field of Search: 364/481, 364/482, 324/57 R, 324/60 R, 324/59, 324/62, 340/347 NT, 343/458
• US Class Current: 702/65
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00

Abstract

Method and apparatus for time lapse based measurement of impedance wherein a series of time measurements are made by voltage transitions with respect to a reference voltage across an unknown component and across a reference component with a known impedance. The time measurements are fed to a microprocessor or other computer means for calculating the impedance of the unknown component.

Claims

1. System for automatic time-based measurement of impedance in an electrical unknown component, comprising:

(a) generating circuit means for generating a sine wave signal of desired measurement frequency,

(b) measurement circuit means containing an unknown impedance component and also including reference resistance means in series with said unknown component across which said sine wave signal is simultaneously applied,

(c) comparator circuit means for receiving the signals applied across the unknown component and across the reference resistance means, said signals being amplified to said comparator circuit means such that they are not subjected to phase sensitive detection nor to analog-to-digital conversion, said comparator circuit means also including reference voltage circuit input means for establishing a reference voltage level and further including polarity reversing circuit input means so that sine wave signals applied to said reference resistance means and said unknown component cross and recross in positive going and negative going transistions the defined reference voltage level to produce detectable and measureable time defined signals,

(d) timing circuit means for receiving signals from said generating circuit means in order to initiate four timing cycles at the same point in time, two each of which said four cycle measure lapses of time with respect to transitions of said sine wave signal across said reference voltage level for each of said unknown component and said reference resistance means to thereby enable calculations by a processor means of impedance based on said timing cycles, and to receive time defined signals from said comparator circuit means, and

(e) processor means for reading said time lapses and for calculating impedance in said unknown component.

2. The time-based impedance measuring system according to claim 1 and in which said generator circuit means includes a crystal controlled oscillator circuit means of predetermined frequency the signal of which is applied to said sine wave generating circuit.

3. The time-based impedance measuring system according to claim 2 and in which said measurement circuit means includes selection switch means for selectively connecting said unknown component and said reference resistance means to said comparator circuit means.

4. The time-based impedance measuring system according to claim 3 and in which a differential amplifier is included between said measurement circuit means and said comparator circuit means for transmitting a sine wave measurement signal of desired amplitude to said comparator circuit means.

5. The time-based impedance measuring system according to claim 4 and in which the output signal of said comparator circuit means is a rectangular wave which said transitions to negative going or positive going states occur when said sine wave measurement signal crosses said defined reference voltage level.

6. The time-based impedance measuring system according to claim 5 and in which said polarity reversing circuit means is connected to said comparator circuit means for receiving the rectangular output signal therefrom for selectively reversing the polarity of said rectangular output signal or transmitting said output signal unchanged to said timing circuit means.

7. The time-based impedance measuring system according to claim 6 and in which reset circuit means are interconnected between said oscillator circuit means and said timing circuit means for reinitiating timing cycles after timing the transitions across said reference voltage level are completed.