Circuit testing device

• US 5,572,143 A
• Filed: 10/19/1993
• Issued: 11/05/1996
• Est. Priority Date: 10/19/1993
• Status: Expired due to Term

• Current Assignee: Stanley Works Limited (Stanley Black & Decker, Inc.)
• Original Assignee: Mac Tools (Stanley Black & Decker, Inc.)
• Inventors: Mellott, James F., Masterman, Jeff, Myers, Dean E.
• Primary Examiner(s): Regan, Maura K.
• Application Number:
  US08/138,711
• Time in Patent Office: 1,113 Days
• Field of Search: 324/555, 324/133, 324/713, 324/556, 324/511, 324/705
• US Class Current: 324/555
• CPC Class Codes: G01R 1/06788 Hand-held or hand-manipulated probes, e.g. for oscilloscopes or for portable test instruments end pieces terminating in a probe H01R11/18
• CPC Class Codes: G01R 19/155 Indicating the presence of voltage
• CPC Class Codes: G01R 19/16557 Logic probes, i.e. circuits indicating logic state (high, low, O); modifications of electronic switches or gates for indicating state of switch H03K17/18
• CPC Class Codes: G01R 19/16561 in hand-held circuit testers see also G01R19/155
• CPC Class Codes: G01R 19/175 Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00

Abstract

A hand held electrical circuit testing for use by technicians to determine circuit conditions such as, whether a duty cycle is present or whether constant voltage is present. The invention makes use of three visual indicating means within a clear body portion of the device which reveal a lighting pattern that will provide an experienced technician with information to determine the circuit condition.

Claims

1. A method for testing a circuit condition of a point in a circuit, comprising the steps of:

connecting a first lead extending from a voltage divider network to a power source;

connecting a second lead extending from said voltage divider network to a ground source;

providing a first constant reference voltage from said voltage divider network to a first op-amp in a first comparator circuit arrangement;

providing a second constant reference voltage from said voltage divider network to a second op-amp in a second comparator circuit arrangement;

providing a third constant reference voltage from said voltage divider network to a third op-amp in a third comparator circuit arrangement;

providing said third constant reference voltage from said divider network to a fourth op-amp in a fourth comparator circuit arrangement;

contacting a probe to a selected circuit point to be tested to provide an input signal to said first and second comparator circuit arrangement;

providing a first output signal from said first comparator circuit through a first RC network to said third comparator circuit and a fifth op-amp circuit in a voltage follower arrangement when said first constant reference voltage is less than the high state of said input signal;

providing a second output signal from said first comparator circuit through said first RC network to said third comparator circuit and said fifth op-amp circuit when said first constant reference voltage is higher than the low state of said input signal, wherein said third comparator circuit is referenced to said third constant reference voltage;

illuminating a first LED when said first comparator circuit transitions from sending said first output signal to sending said second output signal to said third comparator circuit;

illuminating a second LED when said fifth op-amp circuit receives said first output signal from said first comparator circuit;

providing a third output signal from said second comparator circuit through a second RC network to said fourth comparator circuit and a sixth op-amp circuit in a voltage follower arrangement when said second reference voltage is less than the high state of said input signal;

providing a fourth output signal from said second comparator circuit through said first RC network to said fourth comparator circuit and said sixth op-amp circuit when said second constant reference voltage is higher than the low state of the input signal, wherein said fourth comparator circuit is referenced to said third constant reference voltage;

illuminating said first LED when said second comparator circuit transitions from sending said third output signal to sending said fourth output signal to said fourth comparator circuit;

illuminating a third LED when said fourth input signal from said second comparator is provided to said sixth op-amp circuit.

2. The method of claim 1, further comprising:

analyzing the lighting pattern of said red, yellow and green LEDs to determine a percentage duty cycle of said circuit being tested.

3. A circuit testing device comprising:

a body having first and second ends, said body having electrical circuit means contained therein;

a probe communicating with said electrical circuit means and extending from said first end of said body;

a first power lead having a first end communicating with said electrical circuit means and extending from said second end of said body;

a second power lead having a first end communicating with said electrical circuit means and extending from said second end of said body;

first, second and third visual indicating means in association with said electrical circuit means for providing an indication of a circuit condition;

a voltage divider network in communication with said first and second power leads for generating three reference voltages;

a first comparator in communication with said voltage divider network for receiving a first of said reference voltages and also in communication with said probe for receiving an input signal therefrom;

a second comparator in communication with said voltage divider network for receiving a second of said reference voltages and also in communication with said probe for receiving an input signal therefrom;

a third comparator in communication with the output of said first comparator and also in communication with said voltage divider network for receiving a third of said reference voltages, wherein said third comparator is also in communication with said first visual indicator means;

a fourth comparator in communication with the output of said second comparator and also in communication with said voltage divider network for receiving said third of said reference voltages, wherein said fourth comparator is also in communication with said first visual indicator means;

a first voltage follower network in communication with the output of said first comparator and in communication with said second visual indicator means; and

a second voltage follower network in communication with the output of said second comparator and in communication with said third visual indicator means.