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A valve actuator is provided that comprises a unitary housing and a piston translatably mounted within the housing. The piston comprises a first portion having a first diameter and a second portion having a second diameter that is greater than the first diameter. A position sensor having a third dia

A valve actuator is provided that comprises a unitary housing and a piston translatably mounted within the housing. The piston comprises a first portion having a first diameter and a second portion having a second diameter that is greater than the first diameter. A position sensor having a third diameter at least as large as the second diameter is fixedly coupled to the housing and to the piston for determining the position of the piston.

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What is claimed is: 1. A valve actuator, comprising: a unitary housing; a piston translatably mounted within said housing, said piston comprising a first portion having a first diameter and a second portion having a second diameter greater than said first diameter; and a position sensor fixedly cou

What is claimed is: 1. A valve actuator, comprising: a unitary housing; a piston translatably mounted within said housing, said piston comprising a first portion having a first diameter and a second portion having a second diameter greater than said first diameter; and a position sensor fixedly coupled to said housing and to said piston for determining the position of said piston, said position sensor having a third diameter at least as large as the second diameter; wherein said unitary housing includes an inner wall and said second portion is configured to abut said inner wall when said piston is in an extended position. 2. A valve actuator according to claim 1 wherein said position sensor comprises a first section fixedly coupled to said housing and in sealing engagement therewith, said first section having a diameter substantially equal to the third diameter. 3. A valve actuator according to claim 2 wherein said position sensor further comprises a second section fixedly coupled to said first portion and at least partially residing therein, said second section translatably coupled to said first section. 4. A valve actuator according to claim 2 further comprising: a first sealing assembly disposed between an inner surface of said housing and said first portion; a second sealing assembly disposed between an inner surface of said housing and said second portion; and a third sealing assembly disposed between an inner surface of said housing and said first section. 5. A valve actuator according to claim 4 wherein said first and said third sealing assemblies each comprise at least two seals. 6. A valve actuator according to claim 1 wherein said position sensor is a linear variable differential transformer. 7. A valve actuator according to claim 6 wherein said transformer is a dual-channel linear variable transformer. 8. A value actuator according to claim 2 wherein said second portion is configured to abut said first section when said piston is in a retracted position. 9. A valve actuator, comprising: a unitary housing; a piston translatably mounted within said housing, said piston comprising a first portion having a first diameter and a second portion having a second diameter greater than said first diameter; and a position sensor fixedly coupled to said housing and to said piston for determining the translational position of said piston, said position sensor comprising: a first section fixedly coupled to said housing and in sealing engagement therewith, said first section having a third diameter at least as large as the second diameter; and a second section fixedly coupled to said first portion and translatably coupled to said first section; wherein said housing includes an opening at a first end thereof through which said piston and said positioning sensor may be inserted during assembly. 10. A valve actuator according to claim 9 further comprising: a first sealing assembly disposed between said housing and said first portion; a second sealing assembly disposed between said housing and said second portion; and a third sealing assembly disposed between said housing and said first section. 11. A valve actuator according to claim 10 wherein said first and said third sealing assemblies each comprise at least two seals. 12. A valve actuator according to claim 9 wherein said position sensor is a dual-channel linear variable transformer. 13. A valve actuator according to claim 9 wherein said housing includes an inner wall and said second portion is configured to abut said inner wall when said piston is in an extended position and abut said first section when said piston is in a retracted position. 14. A valve actuator according to claim 9 wherein said positioning sensor further comprises a third section having a fourth diameter larger than said third diameter, said third section configured to abut said housing proximate said first end thereof. 15. A valve actuator to be coupled to a pneumatic valve by way of a valve link, comprising: a unitary housing; a piston mounted within said housing and translatable therein to actuate the valve, said piston having a first portion that is coupled to the valve link and having a second portion of a first predetermined diameter; a linear variable differential transformer for determining the linear positioning of said piston within said housing, said sensor comprising: a body having a second predetermined diameter that is at least as large as the first predetermined diameter and having a substantially longitudinal bore therein, said body fixedly coupled to said housing; and a translatable head having a first end that is coupled to said piston and having a second end configured to translate within the longitudinal bore; a first sealing assembly substantially disposed between said housing and said first portion; a second sealing assembly substantially disposed between said housing and said second portion; and a third sealing assembly substantially disposed between said housing and said body. 16. A valve actuator according to claim 15 wherein said first predetermined diameter is substantially equal to said second predetermined diameter. 17. A valve actuator according to claim 15 wherein said body comprises an elongated neck portion having at least a portion of the longitudinal bore formed therein, and wherein said piston has a cavity formed therein for receiving said neck portion proximate said second portion. 18. A valve actuator according to claim 15 wherein said translatable head is coupled to said first portion.