Instrumentation for sensing moisture content of material using a transient thermal pulse

摘要

Instrumentation for sensing moisture content of material using a transient thermal pulse is comprised of a sensing probe (12) having a sensing element (14) in the form of a ribbon excited by a constant current pulse from a source (16) to increase the temperature, and therefore the resistance, of the ribbon linearly. Moisture in web material (10) will limit the increase of temperature during the pulse in proportion to the moisture content. This increase in temperature produces a proportional increase in resistivity which is measured with a Wheatstone bridge (R.sub.1, R.sub.2, R.sub.3, 14) as a change in voltage displayed by a measurement display unit (20). The probe (12) is glued in a shallow groove of a Lucite bar (15c) and connected to copper pins (15a, 15b) embedded in the bar. A cylindrical Lucite block (21) may be used to hold the sensing element (14) connected to axial pins (22a, 22b) in order for the probe to roll and thus reduce its wear.