Detection circuit for measurement of test lead and using the same

• US 20080088317A1
• Filed: 10/13/2006
• Published: 04/17/2008
• Est. Priority Date: 07/12/2006
• Status: Active Grant

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Escort Instruments Corporation (Agilent Technologies, Inc.)
• Inventors: Wu, James, Tsai, Larry, Hsiao, Winston
• Granted Patent: US 7,408,361 B2
• Time in Patent Office: Days
• US Class Current: 324/527
• CPC Class Codes: G01R 31/69 of terminals at the end of a cable or a wire harness; of plugs; of sockets, e.g. wall sockets or power sockets in appliances

Abstract

A low error, plugged test lead detecting circuit for providing accurate current measurement and the method using the same. When a test lead of the plugged detecting circuit is plugged into a split contact jack of the plugged detecting circuit, the circuit stops oscillating during operations for a test lead detecting mode or a fuse open detecting mode. During the test lead detecting mode, if the test lead is plugged into the split contact jack, the oscillating unit stops automatically and outputs a quiescent state. Conversely, if the test lead is unplugged into the split contact jack, the oscillating unit generates a pre-determined frequency pulse according to the oscillating unit. During the fuse open detecting mode, the test lead is plugged into the split contact jack. If a fuse is presented, the oscillating unit stops automatically and outputs a quiescent state. If the fuse is not presented or blown, the oscillating unit generates a pre-determined frequency pulse according to the oscillating unit. During the current measurement mode, the protecting unit and the shunt form a series parallel circuit when the test lead is plugged into the split contact jack. The impedance of the shunt is negligible in comparison to the impedance of the protecting unit, and the voltage drop across the shunt is proportional to the injected current.

Claims

1. A detecting circuit for detecting the contacting condition of a test lead with a split contact jack of an electrical measuring instrument, said plugged test lead detecting circuits comprising:

a shunt coupled to ground and first terminal of said split contact jack;

an oscillating unit coupled to second terminal of said split contact jack through a protecting unit for generating a pulse or a quiescent state output; and

a recognizing unit coupled to said oscillating unit for receiving an output signal transmitted from said oscillating unit, and determining a condition of said plugged test lead detecting circuits by utilizing said oscillating unit.

2. The circuit of claim 1, wherein said split contact jack includes at least two contact plates.

3. The circuit of claim 1, wherein said protecting unit coupled to said oscillating unit has high impedance to prevent error current from oscillating unit into said shunt.

4. The circuit of claim 1, wherein said shunt includes a resistor.

5. The circuit of claim 1, wherein the impedance of said protecting unit is larger than that of said shunt so that the impedance of said shunt can be neglected.

6. The circuit of claim 1, further including a fuse.

7. A detecting method of a detecting circuit with a plugged test lead, comprising:

setting an operation mode of said detecting circuit by a recognizing unit;

transmitting a signal to said recognizing unit by an oscillating unit when said test lead plugs or unplugs into a split contact jack;

receiving said signal from said oscillating unit by said recognizing unit, determining a condition of said detecting circuit; and

sending a message to a user in accordance with said determining result of said recognizing unit.

8. The method of claim 7, wherein said operation mode of said detecting circuit includes a test lead detecting mode, a fuse open detecting mode and a current measurement mode.

9. The method of claim 7, wherein said oscillating unit is stopped oscillating and outputs a quiescent state voltage to said recognizing unit when said plugged test lead is inserted into said split contact jack.

10. The method of claim 7, wherein said oscillating unit generates a pre-determined frequency pulse to said recognizing unit when said test lead is unplugged into said split contact jack.

11. The method of claim 7, wherein said operation mode of said plugged test lead detecting circuit comprises a test lead detecting mode, said oscillating unit outputs a quiescent state voltage to said recognizing unit when said test lead is plugged into said split contact jack, and said recognizing unit sending the message to notice the user without inserting said test lead into said split contact jack.

12. The method of claim 7, wherein said operation mode of said plugged test lead detecting circuit comprises a current measurement mode, said oscillating unit transmits a oscillating signal to said recognizing unit when said test lead is unplugged into said split contact jack, and said recognizing unit sending the message to notice the user inserting said test lead into said split contact jack or checking a fuse open or blown.

13. The method of claim 7, wherein said operation mode of said plugged test lead detecting circuit comprises a fuse open detecting mode, when said test lead is plugged into said split contact jack, said oscillating unit transmitting the oscillating signal to said recognizing unit, said recognizing unit receiving said oscillating signal from said oscillating unit to determine said fuse open or blown, said recognizing unit sending the message to notice the user to replace said fuse.