Compensated capillary indicator

Abstract

A temperature compensated bellows is provided for storage and displacement of a first fluid used as an indicator in a capillary tube. The bellows is made of a housing made of flexible, watertight material. The housing is made up of an upper portion, a lower portion, and an outer accordion formed portion. The accordion formed portion has a length/and is sealingly connected along a periphery between the upper and lower portions. At least one entry/exit port formed on at least one of the portions thereof. At least one of the upper and lower portions extends from a periphery of the accordion formed portion substantially within the housing so as to reduce the storage volume. Preferably, within this area defined by the portion which extends within the housing, a temperature compensation device is disposed. This device is made up of a miniature bellows and reservoir in which a second fluid is placed having a coefficient of expansion which is different than the first fluid. The device is arranged to allow expansion of the second fluid to negatively affect the displacement of the first fluid in the capillary tube. In this manner, the appropriate selection of a first and second fluid allows for temperature compensation, so as to yield an indication which is consistent and accurate across a large range of temperatures.