Claims
- 1. A fieldbus network comprising:
(a) a home run conductor; (b) a spur conductor electrically connected to said home run conductor; and (c) a spur current limiter interposed between said spur conductor and said home run conductor.
- 2. The network of claim 1 further comprising an indicator that current in said spur conductor exceeds a nominal current.
- 3. The network of claim 1 wherein said spur conductor current limiter comprises:
(a) a variable impedance conductor interposed between said spur conductor and said home run conductor; and (b) an impedance adjuster to increase said impedance of said variable impedance conductor in response to electrical current in said spur conductor greater than a nominal current.
- 4. The apparatus of claim 3 wherein said variable impedance conductor comprises a first transistor connected to conduct current between said spur conductor and said home run conductor and having a bias influenced by said impedance adjuster.
- 5. The apparatus of claim 4 wherein said impedance adjuster comprises a second transistor having a bias signal responsive to said current in said spur conductor and connected to reduce said bias of said first transistor in response to an increase in said spur conductor current.
- 6. An apparatus to limit an electrical current in a spur conductor connected a home run conductor of a field bus network comprising:
(a) a variable impedance conductor electrically connecting said spur conductor to said home run conductor; and (b) an impedance adjuster to alter said impedance of said variable impedance conductor in response to a change in current in said spur conductor.
- 7. The apparatus of claim 6 further comprising an indicator that said electrical current in said spur conductor exceeds a nominal current.
- 8. The apparatus of claim 6 wherein said variable impedance conductor comprises a first transistor connected to conduct current between said spur conductor and said home run conductor and having a bias influenced by said impedance adjuster.
- 9. The apparatus of claim 8 wherein said impedance adjuster comprises a second transistor having a bias signal responsive to said current in said spur conductor and connected to reduce said bias of said first transistor in response to an increase in said current in said spur conductor.
- 10. An apparatus to limit current in a spur conductor electrically connected to a home run conductor of a fieldbus network comprising:
(a) a first transistor electrically connected to vary the impedance of said spur conductor in response to a bias signal to said first transistor; and (b) a second transistor electrically connected to vary said bias signal to said first transistor in response to a change in said current in said spur conductor.
- 11. The apparatus of claim 10 further comprising an indicator that said electrical current in said spur conductor exceeds a nominal current.
- 12. An apparatus to limit current in a spur conductor electrically connected to a home run conductor of a fieldbus network comprising:
(a) a first transistor electrically connected to vary the impedance of said spur conductor in response to a bias of said first transistor; (b) a second transistor electrically connected to vary said bias of said first transistor in response to a change in said current in said spur conductor; and (c) an indicator of said current in said spur conductor responsive to said variation of said bias of said first transistor.
- 13. An apparatus to connect a first conductor to a second conductor of a fieldbus network comprising:
(a) a connection block including a conductive connection between a mounting terminal for said first conductor and an first electrical connection arranged for selective engagement; and (b) a current limiter including a conductive connection between a mounting terminal for said second conductor and a second electrical connection arranged for selective engagement with said first electrical connection of said connection block.
- 14. A method for connecting a first conductor and a second conductor of a fieldbus network comprising:
(a) connecting said first conductor to a conductor arranged for selective engagement; (b) connecting said second conductor to an electrically conducting current limiter; and (c) engaging said current limiter and said conductor arranged for selective engagement.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No. 09/771,152, filed Jan. 26, 2001 which is a continuation of application Ser. No. 09/344,408, filed Jun. 24, 1999.
Continuations (2)
|
Number |
Date |
Country |
Parent |
09771152 |
Jan 2001 |
US |
Child |
09866187 |
May 2001 |
US |
Parent |
09344408 |
Jun 1999 |
US |
Child |
09771152 |
Jan 2001 |
US |