ELECTRICAL COMPONENT TESTING APPARATUS HAVING A TEMPERATURE-COMPENSATING CIRCUIT

• US 3,633,098 A
• Filed: 11/17/1969
• Issued: 01/04/1972
• Est. Priority Date: 11/17/1969
• Status: Expired due to Term

• Current Assignee: AT&T, Inc.
• Original Assignee: Robert L. Westlund
• Inventors: Westlund, Robert L.
• Primary Examiner(s): Kubasiewicz, Edward E.
• Application Number:
  US04/877,094
• Time in Patent Office: 778 Days
• Field of Search: 324/57,62,65,64
• US Class Current: 324/721
• CPC Class Codes: G01N 27/041 of a solid body
• CPC Class Codes: G01N 27/046 provided with temperature compensation
• CPC Class Codes: G01R 31/3278 of relays, solenoids or reed switches measuring contact resistance G01R27/205; high voltage magnetic switches G01R31/3271, G01R31/333; testing electric windings G01R31/72; monitoring of fail safe circuits H01H47/002

Abstract

In testing apparatus in which voltages are developed across an electrical component and a standard resistance and are compared to determine whether the resistance of the electrical component falls within desired limits, temperature-compensating circuitry is provided for modifying the voltage developed across the standard resistance in response to changes in temperature and as a direct function of the temperature coefficient of resistance of a specific electrically conducting material in the electrical component. The temperature compensating circuitry is adjustable over a preselected range in accordance with the percentage of the specific electrically conducting material in the electrical component, and is connected between the standard resistance and a comparator circuit so as to feed the modified voltage to the comparator circuit for comparison with the voltage developed across the electrical component.

Claims

1. In apparatus in which a voltage developed across an electrical component and a voltage developed across a standard resistance are fed to a comparing means for determining whether the resistance of the electrical component falls within desired limits, and in which the percentage of a specific electrically conducting material in the electrical component may vary, the improvement which comprises:

temperature-compensating means for modifying the voltage developed across the standard resistance in response to changes in temperature and as a direct function of the temperature coefficient of resistance of the specific electrically conducting material, said temperature-compensating means being adjustable over a preselected range in accordance with the percentage of the specific electrically conducting material in the electrical component and being connected between the standard resistance and the comparing means so as to feed the modified voltage to the comparing means for comparison with the voltage developed across the electrical component.

2. In apparatus as recited in claim 1, the improvement which further comprises:

said temperature-compensating means being responsive to the voltage developed across the standard resistance for developing voltages over a range from a voltage which is representative of an optimum resistance for an electrical component containing zero percent of the specific electrically conducting material to a voltage which is representative of an optimum resistance for an electrical component containing 100 percent of the specific electrically conducting material; and

means for feeding a voltage in accordance with the percentage of the specific electrically conducting material in the electrical component under test, from said temperature-compensating means to the comparing means.

3. In apparatus in which a voltage developed across an electrical component and a voltage developed across a standard resistance are fed to a comparing means for determining whether the resistance of the electrical component falls within desired limits, and in which the percentage of a specific electrically conducting material in the electrical component may vary, the improvement which comprises:

temperature-compensating means for modifying the voltage developed across the standard resistance in response to changes in temperature and as a direct function of the temperature coefficient of resistance of the specific electrically conducting material, said temperature-compensating means including first and second amplifying circuits connected in parallel;

meanS for feeding the voltage developed across the standard resistance to both of said amplifying circuits;

said first amplifying circuit having a constant gain and having an output voltage representative of the voltage developed across the standard resistance;

said second amplifying circuit having a gain which varies in response to changes in temperature and as a direct function of the temperature coefficient of resistance of the specific electrically conducting material; and

having an output voltage which varies in proportion to the voltage developed across the standard resistance as a direct function of the temperature coefficient of resistance of the specific electrically conducting material;

a resistance connected across outputs of said amplifying circuits such that the voltages at successive points on said resistance vary as a function of the temperature coefficient of resistance of the specific electrically conducting material, from a voltage which is representative of an optimum resistance for an electrical component containing a preselected lower percentage of the specific electrically conducting material to a voltage which is representative of an optimum resistance for an electrical component containing a preselected upper percentage of the specific electrically conducting material;

means for tapping voltage off of said resistance in accordance with the percentage of the specific electrically conducting material in the electrical component under test; and

means for feeding the tapped voltage to the comparing means.

4. In apparatus as recited in claim 3, the improvement which further comprises:

said first amplifying circuit having a gain of unity and including an input resistance and a feedback resistance of the same relatively high resistance value, said resistances each having a zero temperature coefficient of resistance; and

said second amplifying circuit including an input resistance and a feedback resistance of the same relatively high resistance value at a fixed reference temperature, the input resistance having a zero temperature coefficient of resistance and the feedback resistance being made of the specific electrically conducting material.