In the filter industry conventional differential pressure indicator devices, which are mounted into the filter housing, generally have only one actuation setting. This setting is based on a predetermined value of differential pressure across the filter element (i.e., the difference in pressure measured upstream and downstream of the filter). When the differential pressure exceeds a certain preload setting, a “pop-up” button and/or electrical signal is activated.Normally the user does not know how long it will take for the filter element to become clogged by the contaminants it continually captures. The user only becomes aware upon actuation that this differential pressure has been reached.The purpose of this paper is to describe a hydraulic fluid monitoring device which has been developed to provide real time, continuous data for the differential pressure developed across a filter within the hydraulic system. Also outlined is a feature of this device which provides an improved solution for the problem of false actuation at low temperatures.