Abstract: A downhole tool is described comprising a housing (24), a fluid flow passage (28) located within (5) the housing (24), and at least one thermoelectric generator (30) located between the fluid flow passage (28) and the housing (24) and operable to generate an electrical output in the event of there being a temperature difference between, in use, the fluid within the fluid flow passage (28), and fluid in contact with the exterior of the housing (24).

Abstract: A downhole tool is described comprising a housing (24), a fluid flow passage (28) located within (5) the housing (24), and at least one thermoelectric generator (30) located between the fluid flow passage (28) and the housing (24) and operable to generate an electrical output in the event of there being a temperature difference between, in use, the fluid within the fluid flow passage (28), and fluid in contact with the exterior of the housing (24).

Abstract: A sensor arrangement is described comprising a sensor housing (28), a first sensor (30) sensitive to a downhole parameter and carried by the housing (28), a second sensor (32) sensitive to the same downhole parameter as the first sensor (30) and carried by the housing (28), the second sensor (32) being spaced apart from the first sensor (30) by a fixed distance D in the axial direction of the housing (28), and a control unit (38) operable to monitor the outputs of the first and second sensors (30, 32) to ascertain information relating to the position, movement and/or related information of the housing (28). A related operating method is also described.